Patent ID: 12230414

DETAILED DESCRIPTION

Embodiments will be described below.

DESCRIPTION OF EMBODIMENTS OF PRESENT DISCLOSURE

Embodiments of the present disclosure will be listed and described. In the following description, the same reference symbols denote the same or corresponding elements, and a description thereof will be omitted.

(1) A vehicle cable according to an embodiment of the present disclosure is a vehicle cable capable of transmitting a signal of 4 GHz or higher. The vehicle cable according to the embodiment includes a two-core cable, a general shield layer that has a braided structure and is disposed on an outer periphery of the two-core cable, and an outer sheath disposed on an outer periphery of the general shield layer. The two-core cable includes two conductors that are a pair of stranded wires arranged in parallel to each other, an insulation layer configured to bundle and cover the two conductors, and a first shield layer including a first metal foil that is disposed on an outer periphery of the insulation layer.

Using a stranded wire as a conductor increases the flexibility, in which the vehicle cable can be easily bent, and the bendability, in which the vehicle cable is not easily broken when bent repeatedly, compared to a case where the conductor is a solid wire instead of a stranded wire.

Also, in the vehicle cable according to the embodiment, since the two conductors are bundled and covered, the material environment between the two conductors can be made uniform easily. Hence, it is possible to sufficiently suppress the insertion loss in high-frequency band signals of 4 GHz or higher, and thus implement a vehicle cable capable of transmitting a high-frequency band signal of 4 GHz or higher.

(2) The first metal foil included in the first shield layer may be in contact with the general shield layer.

Since the first metal foil included in the first shield layer is in contact with the general shield layer, the first shield layer can be easily coupled to an external terminal through, for example, the general shield layer.

(3) A plurality of two-core cables may be included. The plurality of two-core cables may be twisted, and a second shield layer including a second metal foil may be disposed on the outer periphery of the twisted plurality of two-core cables. The general shield layer and the outer sheath may be disposed so as to cover the outer periphery of the second shield layer.

Including the plurality of two-core cables can increase the variety of devices that can be supported.

Furthermore, by disposing the second shield layer on the outer periphery of the two-core cables, an electrical coupling can be formed between the first shield layer and the general shield layer.

(4) The second shield layer includes a double-sided metal tape that is wound helically along the longitudinal direction of the plurality of two-core cables and includes the second metal foil on an upper surface and a lower surface of a substrate. The second metal foil disposed on the upper surface of the substrate may be in contact with the general shield layer.

By helically winding the double-sided metal tape, which includes the metal foil on the upper and lower surface of the substrate, along the longitudinal direction of the plurality of two-core cables, the metal foils disposed on the upper and lower surfaces of the substrate come into contact with each other at an overlapping portion, thus allowing the two members to be electrically coupled. The metal foil disposed on the upper surface of the substrate contacting the general shield layer can form an electrical coupling between the first shield layer of the two-core cable and the general shield layer through the second shield layer. Electrically coupling the first shield layer, the second shield layer and the general shield layer to each other allows the first shield layer and the second shield layer to be easily coupled to an external terminal through the general shield layer. Furthermore, the first shield layer, the second shield layer and the general shield layer can suppress the leakage of signals to the outside of the cable and the introduction of electromagnetic waves from the outside of the cable.

(5) The second metal foil may be made of copper or aluminum.

By using copper or aluminum to form the second metal foil included by the second shield layer, the metal foil can have a uniform and sufficient conductivity. This can suppress the leakage of signals to the outside of the cable and the introduction of electromagnetic waves from the outside of the cable.

(6) The insulation layer may contain one or more types of insulating resins selected from polypropylene and cross-linked polyethylene.

Since polypropylene and cross-linked polyethylene have excellent heat resistance, containing one or more types of insulating resins selected from polypropylene and cross-linked polyethylene increases heat resistance of the insulation layer and the vehicle cable that includes the insulation layer.

(7) The first metal foil may be made of copper or aluminum.

By using copper or aluminum to form the first metal foil included in the first shield, the metal foil can have a uniform and sufficient conductivity. This can suppress the leakage of signals to the outside of the cable and the introduction of electromagnetic waves from the outside of the cable.

(8) The two-core cable includes an insulating tape layer between the insulation layer and the first shield layer. The insulating tape layer may include an insulating tape that is wound helically along the longitudinal direction of the insulation layer and includes an insulating substrate layer containing polyethylene terephthalate.

Polyethylene terephthalate has a higher permittivity than polypropylene, polyethylene, or the like. Hence, when the characteristic impedance of the vehicle cable is to be set to a desired value, providing the insulating tape layer containing polyethylene terephthalate can reduce the size of the insulation layer more than in a case where the insulating tape layer is not provided. Therefore, the size of the vehicle cable can be reduced, and thus the handling of the vehicle cable can be improved.

(9) The thickness of the outer sheath may be 0.3 mm or more to 1.0 mm or less.

Setting the thickness of the outer sheath to 0.3 mm or more to 1.0 mm or less can improve the abrasion resistance, the flame retardancy, and the flexibility of the vehicle cable.

(10) The thickness of the outer sheath may be 0.4 mm or more to 0.8 mm or less.

Setting the thickness of the outer sheath to 0.4 mm or more to 0.8 mm or less can improve the abrasion resistance, the flame retardancy, and the flexibility of the vehicle cable.

Details of Embodiments of Present Disclosure

Specific examples of the vehicle cable according to each embodiment (to be referred to as “the embodiment” hereinafter) of the present disclosure will be described below with reference to the accompanying drawings. Note that the present invention is not limited to these examples. The present invention is intended to be indicated by the appended claims and to include all changes and modifications within the scope of the appended claims and within the meaning and scope of the equivalents of the appended claims.

Vehicle Cable

(1) First Embodiment

FIG.1illustrates a cross-sectional view taken along a plane perpendicular to the longitudinal direction of a vehicle cable10according to the embodiment. InFIG.1, the X-axis direction indicates the height direction of the vehicle cable10, the Y-axis direction indicates the width direction of the vehicle cable10, and the Z-axis direction perpendicular to the page indicates the longitudinal direction of the vehicle cable10.

The inventor of the present invention has investigated a vehicle cable capable of transmitting a signal of 4 GHz or higher, that is, a vehicle cable in which insertion loss with respect to a high-frequency band signal of 4 GHz or higher is suppressed. The inventor has found that a two-core cable including an insulation layer that bundles and covers two conductors for signal transmission can be used to implement a vehicle cable in which insertion loss with respect to a high-frequency band signal of 4 GHz or higher is suppressed. The inventor has completed the invention based on this finding.

Therefore, the vehicle cable according to the embodiment relates to a vehicle cable capable of transmitting a signal of 4 GHz or higher.

The components included by the vehicle cable according to the embodiment will be described hereinafter.

(1-1) Two-Core Cable

As illustrated inFIG.1, the vehicle cable10according to the embodiment includes a two-core cable101including two conductors11that are a pair of stranded wires arranged in parallel to each other, an insulation layer12bundling and covering the two conductors11, and a first shield layer14including a first metal foil disposed on the outer periphery of the insulation layer12. The components included in the two-core cable101will be described below.

(1-1-1) Conductors

The vehicle cable according to the embodiment can include two conductors that are a pair of stranded wires arranged in parallel to each other.

In the interest of enhancing the workability when wiring is performed to attach the vehicle cable to a vehicle, the vehicle cable is required to have flexibility that allows it to be bent easily in accordance with the shape of the attachment position. Also, the vehicle cable may bend repeatedly due to a force being applied in accordance with the movement of a connected component. Thus, the vehicle cable is required to have bendability that curtails breaking when it is bent repeatedly.

Hence, as illustrated inFIG.1, the vehicle cable10according to the embodiment can use a stranded wire as each conductor11for signal transmission. Using a stranded wire as the conductor11increases the flexibility, in which the vehicle cable can be easily bent, and the bendability, in which the vehicle cable is not easily broken when bent repeatedly, compared to a case where the conductor11is a solid wire instead of a stranded wire.

A wire diameter D111of each wire111and the number of the wires111forming the stranded wire of each conductor11are not particularly limited, and can be selected based on the type of signals to be transmitted by the vehicle cable10or the degree of the flexibility or the like required for the vehicle cable10.

(Wire Diameter D111)

The wire diameter D111of each wire forming the stranded wire serving as each conductor11is preferably, for example, 0.100 mm or more to 0.500 mm or less. More preferably, the wire diameter D111may be 0.110 mm or more to 0.220 mm or less. By setting the wire diameter D111to 0.100 mm or more, the productivity of the stranded wire serving as the conductor11can be enhanced while reducing the number of wires used to form the stranded wire serving as the conductor11. In addition, setting the wire diameter D111of each wire forming the stranded wire serving as the conductor11to 0.500 mm or less can increase the flexibility and the bendability of each conductor11and the flexibility and the bendability of the vehicle cable10including the conductors11.

The wire diameter of each wire can be measured and calculated based on the following procedure.

First, in any cross section perpendicular to the longitudinal direction of a wire, the wire diameter of the wire is measured by a micrometer along the two orthogonal diameters of the wire that is being evaluated. An average of the values measured at the aforementioned two locations can be set as the wire diameter of the wire. In this specification, the wire diameter of each wire can be measured and calculated in the same manner.

(Number of Wires)

The number of wires forming the stranded wire serving as the conductor11is not particularly limited. For example, the number of wires is preferably 7 or more to 37 or less, and is more preferably 7 or more to 19 or less. Setting the number of wires that form the stranded wire serving as the conductor11to 7 can increase the flexibility and the bendability of each conductor11as well as the flexibility and the bendability of the vehicle cable10including the conductors11. Furthermore, setting the number of wires foaming the stranded wire serving as the conductor11to 37 or less can enhance the productivity of the stranded wire serving as the conductor11. The number of wires forming the stranded wire serving as the conductor11represents the number of wires included in each conductor11, that is, the number of wires included in each of a conductor11A and a conductor11B.

Each of the conductor11A and the conductor11B can include, for example, the above-described number of wires that have the above-described wire diameter D111, and can be formed by helically twisting the wires along the longitudinal direction. It is preferable for the conductor11A and the conductor11B to be formed by the same wires and the same number of wires. A stranded wire formed by twisting seven strands of wire with a wire diameter of 0.2 mm can be a specific configurational example of each of the conductor11A and the conductor11B.

(Distance L11)

A distance L11between the conductor11A and the conductor11B is not particularly limited. However, it is preferable for the distance L11to be 0.5 mm or more to 3.0 mm or less, and more preferably be 0.8 mm or more to 2.0 mm or less. Setting the distance L11between the conductor11A and the conductor11B to 0.5 mm or more can ensure a sufficient distance between the conductor11A and the conductor11B and can reliably prevent electrical contact between the conductors11A and11B, that is, reliably prevent the generation of short circuits. Also, setting the distance L11between the conductor11A and the conductor11B to 3.0 mm or less can restrain the size of the vehicle cable10while increasing the flexibility of the vehicle cable10.

The distance L11between the conductor11A and the conductor11B represents the distance between the center of the conductor11A and the center of the conductor11B in a cross section perpendicular to the longitudinal direction of the vehicle cable10. The center of the conductor11A and the center of the conductor11B each represents the center of a circumscribed circle of the conductor in a cross section perpendicular to the longitudinal direction of the vehicle cable10.

The distance L11between the conductors can be, for example, a value measured on any cross section perpendicular to the longitudinal direction of the vehicle cable10. However, since the distance L11between the conductors may include a certain amount of variation, it is preferable for the distance L11to be the average of values measured on multiple cross sections perpendicular to the longitudinal direction of the vehicle cable10. For example, it is preferable for the distance L11between the conductors to be the average of the values obtained by measuring the distance between the conductors on 3 or more to 10 or less cross sections, which are perpendicular to the longitudinal direction of the vehicle cable10. Particularly, in the interest of efficiency, it is preferable for the distance L11of the conductors to be the average of the values obtained by measuring the distance between the conductors on three cross sections. When the distance L11between the conductors is to be measured on multiple cross sections perpendicular to the longitudinal direction of the vehicle cable10, the distance between two adjacent measurement surfaces in the longitudinal direction of the vehicle cable10is preferably 10 mm or more to 50 mm or less. For example, the distance between two adjacent measurement surfaces in the longitudinal direction of the vehicle cable10can be 20 mm.

A specific configurational example of the distance L11between the conductor11A and the conductor11B is 1.8 mm.

The conductors11A and11B can be arranged in parallel to each other in the above-described manner. It is preferable for the distance L11between the conductor11A and the conductor11B to be constant. However, even in such a case, the distance L11between the conductor11A and the conductor11B can be within a range that can be considered constant, including manufacturing tolerances.

(Material of Conductors)

The material of each conductor11is not particularly limited, but one or more conductive materials selected from, for example, annealed copper, silver, nickel-plated annealed copper, tin-plated annealed copper, and the like can be used.

(1-1-2) Insulation Layer

The vehicle cable10according to the embodiment can use the insulation layer12that bundles and covers the two conductors11.

Conventionally, in the two-core cable referred to as the Twinax cable, each conductor is covered with an insulation layer, and the two coated wires are subsequently covered by a shield layer or an outer sheath. However, covering each conductor with an insulation layer may generate variation in the thickness of the insulation layers due to manufacturing or may cause the shield layer to fall in a recessed portion between the two coated wires, and thus it is difficult to maintain a uniform environment for, for example, the materials between the two conductors. Hence, it is difficult to implement a cable that is capable of transmitting a high-frequency band signal of, for example, 4 GHz or higher while suppressing insertion loss in a high-frequency band signal of 4 GHz or higher.

In contrast, since the two conductors11are bundled and covered in the vehicle cable according to the embodiment, the the environment for the material between the two conductors11can be made uniform easily. Hence, it is possible to implement a cable that is capable of transmitting a high-frequency band signal of 4 GHz or higher while suppressing insertion loss in the high-frequency band signal of 4 GHz or higher.

Note that the vehicle cable10according to the embodiment suffices to be capable of transmitting a high-frequency band signal of 4 GHz or higher. Although there is no particular upper limit to the frequency band of the signal to be transmitted, it is preferable for the vehicle cable10to be capable of transmitting a signal in a high-frequency band that ranges from, for example, 4 GHz or higher to 30 GHz or lower.

(Size of Insulation Layer)

The size of the insulation layer12is not particularly limited. However, it is preferable for a width W121corresponding to the length of the long axis of the insulation layer12, in a cross section perpendicular to the longitudinal direction of the vehicle cable10, to be 1.5 mm or more to 9.0 mm or less and more preferably to be 1.5 mm or more to 4.0 mm or less.

By setting the width W121to 1.5 mm or more, the surfaces of the conductors11can be covered with the insulation layer12of a sufficient thickness to protect the conductors11while ensuring a sufficient distance between the conductors11. Also, by setting the width W121to 9.0 mm or less, it is possible to restrain the size of the vehicle cable10and improve the handling of the vehicle cable10.

In addition, the height H12corresponding to the length of the short axis of the insulation layer12is preferably 0.75 mm or more to 4.5 mm or less, and is more preferably 0.8 mm or more to 3.5 mm or less.

By setting the height H12of the insulation layer12to 0.75 mm or more, the surfaces of the conductors11can be covered with the insulation layer12of a sufficient thickness to protect the conductors11. Also, by setting the height H12of the insulation layer12to 4.5 mm or less, it is possible to restrain the size of the vehicle cable10and to particularly increase the flexibility of the vehicle cable10.

The insulation layer12can also include a flat part122along the width direction, that is, the Y-axis direction in a cross section perpendicular to the longitudinal direction of the vehicle cable10. Although a width W122of the flat part122is not particularly limited, it is preferable for the width W122to be, for example, 0.5 mm or more to 3.0 mm or less and more preferably to be 0.8 mm or more to 2.5 mm or less.

The vehicle cable10can be easily bent along, for example, the X-axis direction. However, by setting the width W122of the flat part122to be 0.5 mm or more, the vehicle cable10can particularly be bent more easily. That is, the flexibility of the vehicle cable10can be increased.

In addition, by setting the width W122of the flat part122to be 3.0 mm or less, it is possible to restrain the size of the vehicle cable10, and thus improve the handling of the vehicle cable10.

The length of each part of the insulation layer12is not particularly limited, and the length of each part can be selected in the above described manner from, for example, the above-described ranges. For example, as representative values, the width W121can be 3.7 mm, the height H12can be 1.8 mm, and the width W122of the flat part122can be 1.8 mm.

The respective dimensions of the parts of the insulation layer12, that is, the width W121, the width W122of the flat part, and the height H12can be values obtained by measuring, for example, any cross section perpendicular to the longitudinal direction of the vehicle cable10. However, since the length of each part of the insulation layer12of the vehicle cable10may include a certain amount of variation, it is preferable for the length of each part to be the average of values measured on multiple cross sections perpendicular to the longitudinal direction of the vehicle cable10. For example, it is preferable for each of the width W121, the width W122of the flat part, and the height H12described above to be the average of the values obtained by measuring the length of the part on 3 or more to 10 or less cross sections, which are perpendicular to the longitudinal direction of the vehicle cable10. Particularly, in the interest of efficiency, it is preferable for the length of each part to be the average of the values obtained by measuring the length of each part on three cross sections. When the length of each part is to be measured on multiple cross sections perpendicular to the longitudinal direction of the vehicle cable10, the distance between two adjacent measurement surfaces in the longitudinal direction of the vehicle cable10is preferably 10 mm or more to 50 mm or less. For example, the distance between two adjacent measurement surfaces in the longitudinal direction of the vehicle cable10can be 20 mm.

(Material of Insulation Layer)

The material of the insulation layer12is not particularly limited, and can be selected in accordance with the properties required for the vehicle cable10.

The insulation layer12can contain, for example, an insulating resin. The insulating resin is not particularly limited, but is preferable to be one or more types of insulating resins selected from, for example, polypropylene and cross-linked polyethylene. That is, the insulation layer12preferably contains one or more types of insulating resins selected from polypropylene and cross-linked polyethylene.

Since polypropylene and cross-linked polyethylene have excellent heat resistance, containing one or more types of insulating resins selected from polypropylene and cross-linked polyethylene in the insulation layer12increases heat resistance of the insulation layer12and the vehicle cable10that includes the insulation layer12.

Note that since it is typically difficult for polypropylene to be cross-linked, a non-crosslinked polypropylene, which has not been cross-linked, can be suitably used.

The insulation layer12can also contain various types of additives other than the insulating resin described above. The insulation layer12can contain, as an additive, one or more types of additives selected from, for example, a flame retardant, an antioxidant, a cross-linking agent, a cross-linking coagent, a lubricant, and the like.

The flame retardant, the antioxidant, cross-linking agent, and the like are not particularly limited, and known materials can be used as the flame retardant, the antioxidant, cross-linking agent, and the like.

For example, halogenated flame retardants and non-halogenated flame retardants can be used as the flame retardants. Brominated flame retardants or the like can be used as the halogenated flame retardants. Metal hydroxides such as magnesium hydroxide, nitrogen-based flame retardants, antimony trioxide, and phosphate-based flame retardants such as red phosphorus and organophosphates can be used as the non-halogenated flame retardants.

Although the formation method of the insulation layer12is not particularly limited, the material contained in the insulation layer can be formed on the outer periphery of the conductors11by full extrusion molding.

Although a drain wire or the like can be provided other than the above-described conductors11in the insulation layer12, it is preferable not to include a drain wire or the like in the insulation layer12of the vehicle cable according to the embodiment. Since a drain wire is electrically coupled to a shield layer or the like, it is usually used without coating. Hence, if a drain wire is disposed in the insulation layer12, the drain wire may come into contact with the conductors11and cause a short circuit. In contrast, by not disposing a drain wire in the insulation layer12, it is possible to prevent electrical coupling between the conductors11and the drain wire, that is, it is possible to prevent the generation of a short circuit.

In particular, in the vehicle cable10according to the embodiment, it is preferable for the conductors11to be the only electric wires present in the insulation layer12.

(1-1-3) First Shield Layer

The vehicle cable10can include the first shield layer14including a first metal foil disposed on the outer periphery of the insulation layer12.

By including the first shield layer14in the vehicle cable10, it is possible to prevent the leakage of signals to the outside of the cable and to prevent the introduction of electromagnetic waves from the outside of the cable. That is, a shielding effect can be exerted.

Further, it is preferable for the first metal foil included in the first shield layer to be in contact with a general shield layer15(to be described later). The first metal foil included in the first shield layer14being in contact with the general shield layer15allows the first shield layer14to be easily coupled to an external terminal or the like via, for example, the general shield layer15.

Although the configuration of the first shield layer14is not particularly limited, it can include, for example, a metal tape including metal foil helically wound on the outer periphery of the insulation layer12or an insulating tape layer13(to be described later) along the longitudinal direction of the insulation layer12. The first shield layer14can be formed by this aforementioned metal tape. In such a case, the metal foil included by the metal tape is the first metal foil.

As described above, in a case where the first shield layer14includes the metal tape, the configuration of the metal tape is not particularly limited. However, it is preferable for the metal tape to include the metal foil on, for example, at least one of the surfaces of its substrate.

The metal tape used to form the first shield layer14can have, for example, the configuration of a metal tape141whose cross section perpendicular to the longitudinal direction is illustrated inFIG.4A.

The metal tape141illustrated inFIG.4Ahas a structure in which a substrate1411and a metal foil1412are stacked. Hence, the first shield layer14including the first metal foil can be formed by helically winding the metal tape141on the outer periphery of the insulation layer12or the like along the longitudinal direction of the insulation layer12. Note that to form the first shield layer14on the entire outer periphery of the insulation layer12, it is preferable to wind the metal tape141on the outer periphery of the insulation layer12so that the parts of the metal tape141overlap each other.

The metal tape141can also include an adhesive layer1413on a surface of the substrate1411on which the metal foil1412is not disposed. Including the adhesive layer1413in the metal tape141allows the parts of the metal tape141to be adhered together, via the adhesive layer1413, at the overlapping parts of the metal tape141when the metal tape141is helically wound on the outer periphery of the insulation layer12or the like in the longitudinal direction of the insulation layer12. Hence, the shape of the first shield layer14can be stabilized.

In a case where the first shield layer14is to be famed by the metal tape141, it is preferable to wind the metal tape141on the outer periphery of the insulation layer12by positioning a surface141B, which is on the side of the metal foil1412, on the side of the general shield layer15so that the metal foil1412can contact and be electrically coupled to the general shield layer15or the like. In this case, a surface141A, which is on the side of the substrate1411, is positioned on the side of the insulation layer12.

The metal tape used to form the first shield layer14is not limited to the metal tape141. The metal tape used to foam the first shield layer14may be a double-sided metal tape that includes a metal foil on both sides, that is, the upper and lower surfaces, of a substrate as in a double-sided metal tape142illustrated inFIG.4B. The double-sided metal tape142includes an upper metal foil1422on the upper surface of a substrate1421and a lower metal foil1423on the lower surface of the substrate1421.

Even in a case of the double-sided metal tape142illustrated inFIG.4B, an adhesive layer can be provided on either a surface142A of the lower metal foil1423or a surface142B of the upper metal foil1422. Alternatively, an adhesive layer may be provided on both of the surfaces142A and142B.

The size of the metal tape used to form the first shield layer14is not particularly limited. For example, if the metal tape141illustrated inFIG.4Ais used, it is preferable the total of the thicknesses of the metal foil and the substrate, that is, a thickness T141inFIG.4Ais preferably, for example, 5 μm or more to 30 μm or less and is more preferably 10 μm or more to 30 μm or less. By setting the total of the thicknesses of the metal foil and the substrate in the metal tape141illustrated inFIG.4Ato 5 μm or more, the metal foil can be ensured to have a sufficient thickness, and thus enhance a shielding effect. Also, by setting the total of the thicknesses of the metal foil and the substrate to 30 μm or less, it becomes easier to make the metal tape follow the outer shape of the insulation layer12or the like when the metal tape is wound on the outer periphery of the insulation layer12or the like. Hence, the shape of the first shield layer14can be made uniform regardless of its position on the longitudinal direction of the vehicle cable, and the signal transmission performance of the vehicle cable can be stabilized.

If the double-sided metal tape142illustrated inFIG.4Bis used to foam the first shield layer14, it is preferable the total of the thicknesses of the metal foil and the substrate, that is, a thickness T142is preferably, for example, 10 μm or more to 100 μm or less and is more preferably 15 μm or more to 80 μm or less. By setting the total of the thicknesses of the metal foil and the substrate to 10 μm or more, each metal foil can be ensured to have a sufficient thickness, and thus enhance the shielding effect. Also, by setting the total of the thicknesses of the metal foil and the substrate to 100 μm or less, it becomes easier to make the metal tape follow the outer shape of the insulation layer12or the like when the metal tape is wound on the outer periphery of the insulation layer12or the like. Hence, the shape of the first shield layer14can be made uniform regardless of its position on the longitudinal direction of the vehicle cable, and the signal transmission performance of the vehicle cable can be stabilized.

The thicknesses T141and T142are not particularly limited, and can be selected in the above describe manner from, for example, the above-described ranges. For example, as representative values, the thickness T141can be 15 μm, and the thickness T142can be 20 μm.

A thickness T1413of the adhesive layer1413is also not particularly limited. However, it is preferable for the thickness T1413to be, for example, 0.1 μm or more to 10 μm or less, and more preferably to be 0.1 μm or more to 5 μm or less. By setting the thickness T1413of the adhesive layer1413to 0.1 μm or more, a sufficient amount of adhesive can be contained, and the shape of the first shield layer14can be particularly stabilized. Since there is no difference in the stabilizing effect even if the adhesive layer1413is made excessively thick, it is preferable for the thickness T1413to be 10 μm or less as described above in terms of cost. The thickness T1413of the adhesive layer1413is not particularly limited, and can be selected in the above described manner from, for example, the above-described ranges. For example, as a representative value, the thickness T1413can be 2 μm.

In the interest of the shielding effect, the material of the first metal foil included in the first shield layer14suffices to be a conductive material and is not particularly limited. However, it is preferable for the material of the first metal foil to be, for example, copper or aluminum. By using copper or aluminum as the first metal foil included in the first shield layer14, the metal foil can be ensured to have a uniform and sufficient conductivity. This can particularly suppress the leakage of signals to the outside of the cable and the introduction of electromagnetic waves from the outside of the cable.

Note that the material of the substrate1411of the metal tape141or the material of the substrate1421of the double-sided metal tape142is not particularly limited. However, for example, it is possible to use polyethylene terephthalate (PET) as the material of each substrate.

(1-1-4) Insulating Tape Layer

The two-core cable101can also include the insulating tape layer13between the insulation layer12and the first shield layer14described above.

The insulating tape layer13can include an insulating tape130, which is illustrated inFIG.3, that is helically wound on the outer periphery of the insulation layer12along the longitudinal direction of the insulation layer12. Note that the insulating tape layer13can also be formed by the insulating tape130.

FIG.3illustrates a cross section of the insulating tape130in the thickness direction. The insulating tape130can include an insulating substrate layer131containing polyethylene terephthalate (PET). The insulating substrate layer131can also be made of polyethylene terephthalate.

The permittivity of polyethylene terephthalate is higher than those of polypropylene, polyethylene, and the like. Hence, when the characteristic impedance of the vehicle cable10is to be set to a desired value, providing the insulating tape layer13containing polyethylene terephthalate can reduce the size of the insulation layer12more than in a case where the insulating tape layer13is not provided. Therefore, the size of the vehicle cable10can be reduced, and thus the handling of the vehicle cable10can be improved.

The insulating tape130can also include an adhesive layer132on either the upper surface or the lower surface of the insulating substrate layer131. Providing the adhesive layer132allows the parts of the insulating tape130to be adhered together, via the adhesive layer132, at the overlapping portions of the insulating tape130when the insulating tape130is helically wound on the outer periphery of the insulation layer12along the longitudinal direction of the insulation layer12. Hence, the shape of the insulating tape layer13can be stabilized.

Note that when winding the insulating tape130including the adhesive layer132on the outer periphery of the insulation layer12, it is preferable to wind the insulating tape130so that a surface13B on which the adhesive layer132is disposed is positioned on the side of the aforementioned first shield layer14. That is, in this case, it is preferable to arrange the insulating tape130so that a surface13A on which the adhesive layer132is not disposed is positioned on the side of the insulation layer12.

By arranging the surface13A on which the adhesive layer132is not disposed on the side of the insulation layer12, it is possible to prevent the insulation layer12from being adhered to the insulating tape layer13by the adhesive layer132. As a result, the process of removing an outer sheath16or the like and taking out the conductors11at the end of the vehicle cable10in the longitudinal direction can be performed more easily when the vehicle cable10is to be coupled to a device or the like.

Although a thickness T131of the insulating substrate layer131included in the insulating tape130is not particularly limited, it is preferable for the thickness T131to be, for example, 5 μm or more to 80 μm or less, and more preferably to be 5 μm or more to 20 μm or less.

By setting the thickness of the insulating substrate layer131to 5 μm or more, the insulating tape layer, which is the layer containing polyethylene terephthalate that has high permittivity, can be made sufficiently thick, thereby reducing the core formed by the insulation layer12. As a result, the size of the vehicle cable10can be restrained and the flexibility of the vehicle cable10can be increased.

Setting the thickness of the insulating substrate layer131to 80 μm or less can restrain the size of the vehicle cable10and increase the flexibility of the vehicle cable10.

In a case where the insulating tape130includes the adhesive layer132, a thickness T132of the adhesive layer132is not particularly limited. However, it is preferable for the thickness T132to be, for example, 0.1 μm or more to 10 μm or less, and more preferably to be 0.1 μm or more to 5 μm or less.

By setting thickness T132of the adhesive layer132to 0.1 μm or more, a sufficient amount of adhesive can be contained, and the shape of the insulating tape layer13can be particularly stabilized. Since there is no difference in the stabilizing effect even if the adhesive layer132is made excessively thick, it is preferable for the thickness T132to be 10 μm or less as described above in terms of cost.

The thickness T131of the insulating substrate layer131and the thickness T132of the adhesive layer132are not particularly limited, and each thickness can be selected from, for example, the above-described ranges. However, for example, thickness T131of the insulating substrate layer131can be 12 μm, and the thickness T132of the adhesive layer132can be 2 μm.

(1-2) General Shield Layer

The vehicle cable10according to the embodiment can include the general shield layer15that has a braided structure and is disposed on the outer periphery of the two-core cable101.

The general shield layer15can be formed by disposing metal wires so as to form the braided structure as described above. The material of the metal wires included in the general shield layer15is not particularly limited, but a material such as copper, aluminum, a copper alloy, or the like can be used. The surfaces of the metal wires of the general shield layer15may be plated with nickel or tin. Hence, for example, a silver-plated copper alloy, a tin-plated cooper alloy, or the like can also be used as the metal wires of the general shield layer15.

As described above, it is preferable for the general shield layer15to contact and be electrically coupled to the first metal foil of the above-described first shield layer14. In such a case, the first shield layer14can be, for example, easily connected to an external terminal or the like via the general shield layer15.

By providing the general shield layer15together with the above-described first shield layer14, it is possible to reduce the introduction of noise from the outside of the cable and to reduce signal leakage to the outside of the cable. In addition, by electrically coupling the general shield layer15to the above-described first shield layer14, the first shield layer14can be easily connected to an external terminal via the general shield layer15.

Although a thickness T15of the general shield layer15is not particularly limited, it is preferable for the thickness T15to be 0.1 mm or more to 0.5 mm or less and more preferably be 0.1 mm or more to 0.3 mm or less.

By setting the thickness T15of the general shield layer15to 0.1 mm or more, it is particularly possible to reduce the introduction of noise from the outside of the cable and to reduce signal leakage to the outside of the cable. Also, by setting the thickness T15of the general shield layer15to 0.5 mm or less, the flexibility of the vehicle cable10can be increased.

The thickness T15of the general shield layer15can be freely selected from, for example, the above-described ranges. However, as a representative value, the thickness T15of the general shield layer15can be, for example, 0.2 mm.

The thickness T15of the general shield layer15can be measured and calculated by, for example, the following procedure.

The thickness of the general shield layer15is measured by measuring, by a micrometer, a total of two locations in any cross section perpendicular to the longitudinal direction of the vehicle cable10. The two locations to be measured by the micrometer are a location along the width direction of the vehicle cable10and a location along the height direction of the vehicle cable10. Note that the width direction is the Y-axis direction inFIG.1and can also be called the long hand direction. The thickness direction is the X-axis direction inFIG.1and can also be called the short hand direction.

Subsequently, the average of the measure values obtained by measuring the two locations can be set as the thickness T15of the general shield layer15.

The thickness T15of the general shield layer15can be a value obtained by measuring any cross section perpendicular to the longitudinal direction of the vehicle cable10. However, as the thickness T15of the general shield layer15may include a certain amount of variation, it is preferable for the thickness T15to be the average of values measured on multiple cross sections perpendicular to the longitudinal direction of the vehicle cable10. For example, it is preferable for the thickness T15of the general shield layer15to be the average of the values obtained by measuring the thickness T15on 3 or more to 10 or less cross sections, which are perpendicular to the longitudinal direction of the vehicle cable10, in the above-described manner. Particularly, in the interest of efficiency, it is preferable for the length of each part to be the average of the values obtained by measuring the thickness T15on three cross sections. When the length of each part is to be measured on multiple cross sections perpendicular to the longitudinal direction of the vehicle cable10, the distance between two adjacent measurement surfaces in the longitudinal direction of the vehicle cable10is preferably 10 mm or more to 50 mm or less. For example, the distance between two adjacent measurement surfaces in the longitudinal direction of the vehicle cable10can be 20 mm.

A thickness T16of the outer sheath16can also be measured in the same manner.

(1-3) Outer Sheath

The vehicle cable according to the embodiment includes the outer sheath16that is disposed on the outer periphery of the general shield layer15. By providing the outer sheath16, the two-core cable101and the general shield layer15that are disposed inside of the cable can be protected.

Although the material of the outer sheath16is not particularly limited, it can contain one or more types of resin selected from, for example, polyolefin resins such as polyethylene and polypropylene, and polyvinyl chloride and the like. The resin of the outer sheath16may be cross-linked or may not be cross-linked.

In addition to the above-described resins, the outer sheath16can contain additives such as flame retardants, flame retardant coagents, antioxidants, lubricants, colorants, reflective additives, concealers, processing stabilizers and plasticizers.

Although the formation method of the outer sheath16is not particularly limited, the outer sheath16can be formed by performing filled extrusion molding or drawdown extrusion molding by using, for example, the above-described materials contained in the outer sheath16.

The thickness T16of the outer sheath16is not particularly limited. However, for example, it is preferable for the thickness T16to be 0.2 mm or more to 1.2 mm or less, more preferably be 0.3 mm or more to 1.0 mm or less, and even more preferably be 0.4 mm or more to 0.8 mm or less.

By setting the thickness T16of the outer sheath16to 0.2 mm or more, the two-core cable101and the general shield layer15inside the cable can be sufficiently protected. Also, by setting the thickness T16of the outer sheath16to 1.2 mm or less, the size of the vehicle cable10can be restrained, and the flexibility of the vehicle cable10can be increased.

Also, setting the thickness T16of the outer sheath16to 0.3 mm or more to 1.0 mm or less, or more particularly to 0.4 mm or more to 0.8 mm or less can particularly improve the abrasion resistance, the flame retardancy, and the flexibility of the vehicle cable.

The thickness T16of the outer sheath16can be freely selected from, for example, the above-described ranges. However, as a representative value, the thickness T16of the outer sheath16can be, for example, 0.5 mm.

Since the thickness T16of the outer sheath16can be measured in a similar manner to the thickness T15of the general shield layer15describe above, a description thereof will be omitted.

(2) Second Embodiment

The vehicle cable according to the embodiment can also include a plurality of two-core cables in accordance with the device to be coupled.

As illustrated inFIG.2, a vehicle cable20according to the embodiment can include the plurality of two-core cables101. In this case, the plurality of two-core cables101are twisted together, and a second shield layer24including a second metal foil on the outer periphery of the twisted plurality of two-core cables101can be arranged in the vehicle cable20.

The general shield layer15and the outer sheath16described above can be disposed to cover the outer periphery of the second shield layer24.

Including the plurality of two-core cables101in the vehicle cable20according to the embodiment in the above described manner can increase the types of devices that can be supported by the vehicle cable20.

Note that a description of some of the matters already described in the first embodiment with respect to the two-core cable101and the like will be omitted. The components included in the vehicle cable10according to the embodiment will be described hereinafter.

(2-1) Two-Core Cables

The vehicle cable20illustrated inFIG.2includes two two-core cables101. However, the vehicle cable according to the embodiment can also include three or more two-core cables.

The plurality of two-core cables101can be helically twisted with each other along the longitudinal direction. At this time, the twist rate is not particularly limited and can be selected in accordance with the size of the twisted units. However, for example, it is preferable for the twist rate to be 100 mm or more to 300 mm or less. Note that each two-core cable101includes, as described above, two conductor11that are two stranded wires arranged in parallel to each other, the insulation layer12configured to bundle and cover the two conductors11, and the first shield layer14disposed on the outer periphery of the insulation layer12. The insulating tape layer13can also be provided between the first shield layer14and the insulation layer12.

Since the two-core cable101has already been described, a description thereof will be omitted here.

(2-2) Second Shield Layer

The second shield layer24can be disposed on the outer periphery of the twisted plurality of two-core cables101, and can be disposed so as to be in contact with the respective outer peripheries (outer surfaces) of the two-core cables101. Disposing the second shield layer on the outer periphery of the two-core cable allows an electrical coupling to be formed between the first shield layer14and the general shield layer15.

The second shield layer24preferably includes a metal tape that can include the second metal foil and be helically wound along the longitudinal direction of, for example, the plurality of two-core cables101. To form the second shield layer24so as to cover the entirety of the plurality of two-core cables101, it is preferable to wind the metal tape around the outer periphery of the plurality of two-core cables101so that parts of the metal tape will overlap each other.

It is preferable for the metal tape included in the second shield layer24to be a double-sided metal tape that includes a metal foil on both surfaces of the substrate. That is, it is preferable for the metal tape included in the second shield layer24to include the upper metal foil1422on the upper surface of the substrate1421and the lower metal foil1423on the lower surface of the substrate1421as in the double-sided metal tape142illustrated inFIG.4B. It is also preferable for the upper metal foil1422, which is the metal foil disposed on the upper surface of the substrate1421, to be in contact with the general shield layer15. It is also preferable for the lower metal foil1423, which is the metal foil disposed on the lower surface of the substrate1421, to be in contact with the first metal foil of the first shield layer14. In this case, the upper metal foil1422and the lower metal foil1423form the second metal foil included in the second shield layer24.

By helically winding a double-sided metal tape, which includes the metal foil on the upper and lower surface of the substrate1421, along the longitudinal direction of the plurality of two-core cables101, the upper metal foil1422and the lower metal foil1423can come into contact at overlapping portions and be electrically coupled. The upper metal foil1422disposed on the upper surface of the substrate1421contacting the general shield layer15allows, for example, the first shield layer14of each two-core cable101to be electrically coupled to the general shield layer15via the second shield layer24. By electrically coupling the first shield layer14, the second shield layer24, and the general shield layer15as described above, the first shield layer14and the second shield layer24can be easily connected to an external terminal via the general shield layer15. Further, the first shield layer14, the second shield layer24, and the general shield layer15can be used to suppress signal leakage to the outside of the cable and to suppress the introduction of electromagnetic waves from the outside of the cable.

In the interest of the shielding effect, the material of the second metal foil included in the second shield layer24suffices to be a conductive material and is not particularly limited. However, it is preferable for the material of the second metal foil to be, for example, copper or aluminum. By using copper or aluminum as the second metal foil of the second shield layer24, the metal foil can be ensured to have a uniform and sufficient conductivity. This can particularly suppress the leakage of signals to the outside of the cable and the introduction of electromagnetic waves from the outside of the cable.

As the preferable thicknesses of the respective portions of the double-sided tape illustrated inFIG.4Bhave already been described, a description thereof will be omitted here.

(2-3) General Shield Layer and Outer Sheath

The general shield layer15and the outer sheath16can be formed in the same manner as in the first embodiment. Hence, a description thereof will be omitted.

EXAMPLES

Although specific examples of the embodiment will be described hereinafter, the present invention is not limited to these examples.

Experiment Example 1

The vehicle cable10(to be also referred to as “the cable of configuration 1” hereinafter) that has the cross-sectional structure illustrated inFIG.1and a cable50(to be also referred to as “the cable of configuration 2” hereinafter) that has the cross-sectional structure illustrated inFIG.5were prepared, and the skew and the insertion loss of each cable were evaluated.

The cable of configuration 1 is the example of the embodiment, and the cable of configuration 2 is the comparative example.

(1) Configuration of Cables

(Cable of Configuration 1)

The vehicle cable10having the cross-sectional structure illustrated inFIG.1is famed according to CONFIGURATION 1 indicated in TABLE 1. More specifically, the vehicle cable10included two conductors11. Each conductor11was formed by twisting 7 wires111that were tin-plated copper wires. The wire diameter D111of each wire111was 0.16 mm. The diameter of each conductor11was 0.48 mm.

TABLE 1CONFIGURATION 1CONFIGURATION 2CONFIGURATION 3REFERENCELENGTHREFERENCELENGTHREFERENCELENGTHSYMBOL(THICKNESS)SYMBOL(THICKNESS)SYMBOL(THICKNESS)WIRE DIAMETERD1110.16D5110.16D610.41(CONDUCTORDIAMETER)(mm)DISTANCEL111.48L511.23L611.40BETWEENCONDUCTORS(mm)SIZE OFW1212.96D521.23W6212.80INSULATIONH121.48H621.40LAYER(mm)TWIST RATE—52A, 52B12—(mm)INSULATINGT13112T13112T13112TAPE LAYER(μm)FIRSTT14115T14115T14115SHIELD LAYER(μm)GENERALT150.4T550.4——SHIELD LAYER(mm)OUTER SHEATHT160.5T560.5——(mm)

The measurement of the wire diameter was performed in accordance with the following procedure. First, in any cross section perpendicular to the longitudinal direction of the wire, the diameter of the wire was measured by a micrometer along the two orthogonal diameters of the wire. The average of the measured values obtained in the aforementioned two locations was obtained as the wire diameter. The conductor diameter was also measured and calculated in a similar manner.

The two conductors11are arranged in parallel to each other, and the insulation layer12bundles and covers the two conductors11. Polypropylene was used for the material of the insulation layer12, and no cross-linking was performed. The distance L11between the conductors11and the width W121and the height H12of the insulation layer12were as indicated in TABLE 1. Note that the distance between the conductors11correspond to the distance between the respective centers of the circumscribed circles of the conductors11.

The distance L11between the conductors11and the width W121and the height H12of the insulation layer12were measured and calculated according to the following procedure. The procedure will be described by using the distance L11between the conductors11as an example.

The distance L11between the conductors11was measured on each of the acquired three cross sections perpendicular to the longitudinal direction of the vehicle cable. The average of the measured values thereof was set as the distance L11between the conductors11of the vehicle cable. The three measured cross sections were set so that the distance between adjacent cross sections was 20 mm in the longitudinal direction of the cable. The width W121and the height H12of the insulation layer12were measured in the same manner.

The insulating tape layer13, the first shield layer14, the general shield layer15, and the outer sheath16are disposed on the outer periphery of the insulation layer12. The thickness of each layer is as indicated in TABLE 1.

The insulating tape layer13was formed using the insulating tape130illustrated inFIG.3. Hence, the thickness T131of the insulating substrate layer131is indicated as the thickness of the insulating tape layer in TABLE 1. The insulating substrate layer131was made of polyethylene terephthalate.

The first shield layer14was formed by using the metal tape141illustrated inFIG.4A. Hence, the thickness T141as the total of the thicknesses of the substrate1411and the metal foil1412in the metal tape141is indicated in TABLE 1. The substrate1411is made of polyethylene terephthalate, and the metal foil1412is made of aluminum foil.

When the insulating tape layer13and the first shield layer14were formed, the insulating tape130and the metal tape141were helically wound along the longitudinal direction of the insulation layer12so that the adhesive layer132of the insulating tape130and the adhesive layer1413of the metal tape141would adhere. That is, the insulating tape130was wound so that the surface13A was positioned on the side of the insulation layer12, and the metal tape141was wound so that the surface141A was positioned on the side of the insulation layer12.

Tin-plated copper wires were used as the wires forming the general shield layer15. Polyethylene was used as the resin material of the outer sheath16, and cross-linking was performed.

The thickness T15of the general shield layer15and the thickness T16of the outer sheath16were measured and calculated according to the following procedure. The procedure will be described using the case of the general shield layer15as an example.

First, in each of the acquired three cross sections perpendicular to the longitudinal direction of the vehicle cable10, the thickness T15was measured by a micrometer at a total of two locations, that is, one location along the width direction and the one location along the height direction of the vehicle cable10. The average of the measured values of the two locations was set as the thickness T15of the general shield layer15at each cross section.

Next, the average of all of the thicknesses T15of the general shield layer15that were individually calculated for the three cross sections was obtained and set as the thickness T15of the general shield layer15of the vehicle cable. The three measured cross sections were set so that the distance between adjacent cross sections was 20 mm in the longitudinal direction of the cable.

The thickness T16of the outer sheath16was also measured and calculated in a similar manner to the thickness T15of the general shield layer15.

(Cable of Configuration 2)

The cable50that has the cross-sectional structure illustrated inFIG.5has the configuration of CONFIGURATION 2 indicated in TABLE 1. More specifically, the cable50included two conductors51. Each conductor51was formed by twisting 7 wires511that were tin-plated copper wires. A wire diameter D511of each wire511were 0.16 mm. The outer diameter of each conductor51was 0.48 mm.

The wire diameter of each wire and the outer diameter of each conductor were measured and evaluated in a similar manner to the cable of configuration 1.

The conductors51were formed as coated wires52A and52B, each of which with an insulation layer521disposed on the outer periphery. The two coated wires52A and52B were twisted at a twist rate of 12 mm. Cross-linked polyethylene was used for the insulation layer of each of the coated wires52A and52B.

The outer diameter D52of each coated wire was 1.23 mm, and a distance L51between the conductors51was 1.23 mm. Note that the distance L51between the conductors51correspond to the distance between the respective centers of the circumscribed circles of the conductors51.

The outer diameter D52of each coated wire was evaluated in the same manner as the wire diameter. The distance L51between the conductors51was evaluated in the same manner as the cable of configuration 1.

A insulating tape layer53, a first shield layer54, a general shield layer55, and an outer sheath56are disposed on the outer periphery of the two coated wires52A and52B. The respective thicknesses of the layers are as indicated in TABLE 1.

The insulating tape layer53to the outer sheath56were famed in the same manner as the vehicle cable10of configuration 1 described above.

Since the length of each of the insulating tape layer53to the outer sheath56was measured and calculated in the same manner as the cable of configuration 1, a description thereof will be omitted.

(2) Evaluation

(Skew)

A digital serial analyzer was used to send electric pulses to the two conductors of the cable of the configuration 1 described above and to the two conductors of the cable of configuration 2, and the skew was obtained by measuring the delay time per meter. 20 cables of the same configuration were measured for each of the cable of configuration 1 and the cable of configuration 2.

In the case of the vehicle cable10of configuration 1, it was confirmed that skew was distributed in the range of 0 psec/m or more to 4 psec/m or less.

In contrast, in the case of the cable50of configuration 2, it was confirmed that skew was distributed in the range of 0 psec/m or more to 15 psec/m or less.

That is, it was confirmed that the delay time was suppressed more in the vehicle cable10of configuration 1 than in the cable50of configuration 2.

(Insertion Loss)

Differential signals were input to each of the cable of configuration 1 and the cable of configuration 2 to evaluate the frequency characteristics of insertion loss. The evaluation was carried out in air at room temperature. The results are indicated inFIG.7. InFIG.7, line71indicates the evaluation result of the cable of configuration 1, and line72indicates the evaluation result of the cable of configuration 2.

As is obvious fromFIG.7, it was confirmed that the cable of configuration 1 according to the example is able to transmit signals of 4 GHz or higher, particularly, signals of 5 GHz or higher. Note that although it is indicated inFIG.7that signals can be transmitted without a large insertion loss in frequency bands of 10 GHz or less, it was confirmed that signals are also able to be transmitted without a large insertion loss in higher frequency bands, for example, in frequency bands higher than 10 GHz.

In contrast, with respect to the cable of configuration 2 according to the comparative example, a large insertion loss was confirmed when the frequency band exceeded 4 GHz, and it was confirmed that the cable of configuration 2 is not applicable for transmitting signals of 4 GHz or higher.

Experiment Example 2

The abrasion resistance, the flame retardancy, and the flexibility of the vehicle cable10, which has the cross-sectional shape indicated inFIG.1, were evaluated. EXPERIMENT EXAMPLES 2-1 to 2-6 all are examples of the embodiment.

In each experiment example, the vehicle cable10were manufactured in the same manner as configuration 1 of EXPERIMENT EXAMPLE 1 except that the thickness of the outer sheath16was adjusted to be the value indicated in TABLE 2.

The abrasion resistance was evaluated by performing a tape test in compliance with JASO D618. The coated wire of each sample was cut to a length of 1000 mm, and #150G abrasion tape was pressed on to the coated wire with a pressing load of 1.9 kg. Subsequently, the tape was sent out at a tape moving speed of 1500 mm/min, and the amount of the tape that was sent out was measured until the conductors were exposed.

Flame retardancy was evaluated by performing a horizontal burning test in compliance with JASO-D618. In the horizontal burning test, the underside of the center of the electric wire, held horizontally, was brought into contact with the flame of a tirrill burner at an angle of 20° for 30 seconds, and the time until the flame was extinguished was measured.

Flexibility was evaluated by placing an evaluation cable80with a length of 50 cm on a table81as illustrated inFIG.8, thus setting a state where the cable80protrudes 25 cm from the table81. That is, a length L801and a length L802inFIG.8each were 25 cm.

In this case, an evaluation was performed by measuring a distance L80between a ground82and an end80A of the cable80. The bend of the vehicle cable increases as shorter the distance L80is, thus indicating better flexibility.

With respect to abrasion resistance, a case that was 250 cm or more was evaluated as A, a case that was 200 cm or more but less than 250 cm was evaluated as B, and a case that was 200 cm or less was evaluated as C. An evaluation of A represents a case with the best abrasion resistance, that is, a case that can withstand abrasion. The abrasion resistance decreases in the order of evaluations B and C.

With respect to flame retardancy, a case that was 30 seconds or less was evaluated as A, a case that was 30 seconds or longer to 40 seconds or less was evaluated as B, and a case that was longer than 40 seconds was evaluated as C. An evaluation of A represents a case with the best flame retardancy, that is, a case that can withstand burning. The flame retardancy decreases in the order of evaluations B and C.

With respect to flexibility, a case that was 130 mm or less was evaluated as A, a case that was 130 mm or longer to 135 mm or less was evaluated as B, and a case that was longer than 135 mm was evaluated as C. An evaluation of A represents a case with the best flexibility, that is, a case that can be bent easily. The flexibility decreases in the order of evaluations B and C.

As the overall evaluation, for the three types of evaluations described above, an evaluation of C was given when at least one C was contained, an evaluation of B was given when no C was contained but at least one B was contained, and an evaluation of A was given when all the three types of evaluations were A.

TABLE 2 indicates the thickness of the outer sheath of the vehicle cable subjected to the evaluation and the evaluation results.

TABLE 2ABRASIONTHICKNESSRESISTANCEFLAME RETARDANCYFLEXIBILITYOF OUTERMEASUREDMEASUREDMEASUREDOVERALLSHEATHVALUEEVALUA-VALUEEVALUA-VALUEEVALUA-EVALUA-(mm)(cm)TION(sec)TION(mm)TIONTIONEXPERIMENT1.2882A10A140CCEXAMPLE 2-1EXPERIMENT1.0735A14A133BBEXAMPLE 2-2EXPERIMENT0.8588A20A127AAEXAMPLE 2-3EXPERIMENT0.4294A26A121AAEXAMPLE 2-4EXPERIMENT0.3220B36B115ABEXAMPLE 2-5EXPERIMENT0.2147C57C109ACEXAMPLE 2-6

According to the results indicated in TABLE 2, the overall evaluation result was A or B in cases where the thickness T16of outer sheath16was 0.3 mm or more to 1.0 mm or less, confirming excellence in abrasive resistance, flame retardancy, and flexibility. Furthermore, the overall evaluation result was A in cases where the thickness T16of outer sheath16was 0.4 mm or more to 0.8 mm or less, confirming particular excellence in abrasive resistance, flame retardancy, and flexibility.

Experiment Example 3

In addition to evaluations performed on the cable of configuration 1 and the cable of configuration 2 in EXPERIMENT EXAMPLE 1, a cable of configuration 3 was prepared and evaluated for bendability.

EXPERIMENT EXAMPLE 3-1 indicates the evaluation result of the vehicle cable of configuration 1 and is an example of the embodiment.

EXPERIMENT EXAMPLE 3-2 indicates the evaluation result of the vehicle cable of configuration 2 and is a comparative example.

EXPERIMENT EXAMPLE 3-3 indicates the evaluation result of the vehicle cable of configuration 3 and is a comparative example.

(1) Cable of Configuration 3 The cable of configuration 3 has a cross-sectional structure illustrated inFIG.6, and includes two conductors61that are solid wires instead of stranded wires. The conductor diameter D61of the conductor61was 0.41 mm as indicated in TABLE 1, and a distance L61between the conductors was 1.4 mm. A tin-plated copper wire was used as each conductor61.

The two conductors61are bundled and covered by an insulation layer62. Polypropylene was used for the material of the insulation layer62, and no cross-linking was performed. A width W621of the insulation layer62was 2.80 mm, and a height H62of the insulation layer62was 1.40 mm.

A drain wire612was also disposed in the insulation layer62.

An insulating tape layer63and a first shield layer64were disposed on the outer periphery of the insulation layer62. The insulating tape layer63and the first shield layer64were formed in the same manner as the cable of configuration 1 in EXPERIMENT EXAMPLE 1.

Since the insulating tape layer63was formed by using the insulating tape130illustrated inFIG.3, the thickness T131of the insulating substrate layer131is indicated as the thickness of the insulating tape layer63in TABLE 1. Also, since the first shield layer64was formed by using the metal tape141illustrated inFIG.4A, the thickness T141, which is the total of the thicknesses of the substrate1411and the metal foil1412in the metal tape141, is indicated in TABLE 1 as the thickness of the first shield layer64.

The general shield layer and the outer sheath were not provided.

As the cable of configuration 1 and the cable of configuration 2 have the same configurations as those in the case of EXPERIMENT EXAMPLE 1, a description thereof will be omitted here.

(2) Evaluation

The bendability evaluation was performed by placing, as illustrated inFIG.9, a cable90to be evaluated between two mandrels911and912, which were arranged horizontally and parallel to each other and had a diameter of 4 mm, and applying a load of 200 g vertically downward on the cable90. In this state, an operation in which the upper end of the cable90is bent 90° in the horizontal direction to be abutted against the upper side of one mandrel911, and is subsequently bent 90° in the horizontal direction to be abutted against the upper side of the other mandrel912was repeatedly performed.

The repeated operation described above was performed by measuring the resistance values of all of the conductors in the cable90. The number of bending operations performed until the resistance increased to 10 times or more of the initial resistance value was counted with respect to one of the conductors. Note that one bending operation comprises an operation in which the cable is first bent to the left side, then bent to the right side, and subsequently returned to the left side. The superiority of the bendability increases as the number of bending operations, as a result of the bending test, increases.

Three cables were prepared for the same configuration, and three evaluations were performed. The average value of the three evaluation is also indicated.

Each evaluation result is indicated by a converted value obtained by converting the number of bending operations of the first test of EXPERIMENT EXAMPLE 3-2 as 100. The superiority of the bendability increases as this numerical value increases. For example, the number of bending operations of the first test of EXPERIMENT EXAMPLE 3-1 is 2.7 times higher than the number of bending operations of the first test of EXPERIMENT EXAMPLE 3-2. The evaluation results are indicated in TABLE 3.

TABLE 3EXPERIMENTEXPERIMENTEXPERIMENTEXAMPLEEXAMPLEEXAMPLE3-13-23-3FIRST27010025EVALUATIONSECOND33013030EVALUATIONTHIRD29011045EVALUATIONAVERAGE29711333
According to the results indicated in TABLE 3, it was confirmed that the cable of EXPERIMENT EXAMPLE 3-1 which is the example of the embodiment has superior bendability.

In contrast, it was confirmed that the cable of EXPERIMENT EXAMPLE 3-3 has a particularly inferior bendability because the conductor was not a stranded wire.