Cable

A cable has a core made of an insulated wire, a shield layer provided at an outer periphery of the core, a reinforcing layer provided at an outer periphery of the shield layer, and a sheath provided at an outer periphery of the reinforcing layer. The insulated wire has a wire conductor and an insulating layer covering an outer periphery of the wire conductor. The shield layer is formed from tinsel-coppers. Each of the tinsel-copper has a core string and a copper foil provided around the core string. The reinforcing layer is formed by braiding fibers.

The present application is based on Japanese Patent Application No. 2008-287381 filed on Nov. 10, 2008, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cable, in more particular, to a cable in which a shield is provided around an electric wire.

2. Related Art

Conventionally, a cable comprising an insulated wire comprising a center conductor and an insulation for covering the center conductor, a shield layer provided at an outer periphery of the insulated wire, in which the shield layer is formed by braiding collected wires, each of the collected wires is composed of a plurality of shield wires arranged in parallel, and a friction coefficient of two shield wires provided at both sides of the collected wire is smaller than a friction coefficient of other shield wires has been known. Japanese Patent Laid-Open No. 2006-031954 (JP-A 2006-031954) discloses an example of such a conventional cable.

In the cable disclosed by JP-A 2006-031954, the friction coefficient of the shield wires provided at the both sides of the collected wire is smaller than the friction coefficient of the other shield wires. Therefore, when flexural motion is applied repeatedly to the cable in an operating environment, friction between the shield wires can be reduced, so that it is possible to provide a cable having a high flex resistance property.

However, there are following disadvantages in the conventional cable as disclosed by JP-A 2006-031954. For example, when being disposed between a body of a vehicle and a part beneath a spring of the vehicle (a lower part with respect to a suspension spring), the shield wires composing the shield layer may be broken or disconnected because of flexion (bending) due to up-and-down movement (bound and rebound) of wheels and a torsion applied at the time of steering of the wheels. Therefore, the conventional cable may be inferior in the flex resistance property, tensile strength and reliability.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a cable which is excellent in the flex resistance property, tensile strength and reliability.

According to a feature of the invention, a cable comprises:

a core comprising an insulated wire, the insulated wire comprising a wire conductor and an insulating layer covering an outer periphery of the wire conductor;

a shield layer provided at an outer periphery of the core, the shield layer comprising a tinsel-copper comprising a core string and a copper foil provided around the core string;

a reinforcing layer provided at an outer periphery of the shield layer, the reinforcing layer comprising a braid of a fiber, and

a sheath provided at an outer periphery of the reinforcing layer.

In the cable, the shield layer may comprise a braid of the tinsel copper.

In the cable, the shield layer may comprise the tinsel copper spirally wound on the outer periphery of the core.

In the cable, the tinsel copper may further comprise a plating film on a surface of the tinsel copper.

In the cable, the fiber may comprise at least one material selected from a group comprising polyvinyl alcohol, polyethylene terephthalate, and polyethylene-2,6-naphthalate.

In the cable, the sheath may comprise a rubber material including an ethylene-α-olefin-polyene copolymer comprising a polyene that is a norbornene compound containing a vinyl group at terminal, and a SiH radical-containing compound comprising a plurality of SiH radicals in one molecular.

In the cable, the sheath may comprise a rubber material comprising at least one material selected from a group comprising ethylene-propylene-diene rubber, styrene-butadiene rubber, butyl rubber, nitrile rubber, and chloroprene rubber.

ADVANTAGES OF THE INVENTION

According to the cable of the present invention, it is possible to provide a cable which is excellent in the flex resistance property, tensile strength and reliability.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferred Embodiment

Next, a preferred embodiment of the present invention will be explained in more detail in conjunction with appended drawings.

FIG. 1Ais a perspective view of a cable in a preferred embodiment according to the invention, andFIG. 1Bis a lateral cross sectional view along A-A of the cable shown inFIG. 1A.

A cable1in the preferred embodiment comprises a core5comprising four pieces of insulated wire10, the insulated wire10comprising a linear conductor (wire conductor)12and an insulating layer14which covers an outer periphery of the conductor12, a shield layer20provided at an outer periphery of the core5and having a shield function, a reinforcing layer30provided at an outer periphery of the shield layer20, and a sheath40provided at an outer periphery of the reinforcing layer30. InFIG. 1AandFIG. 1B, the core5comprises four pieces of the insulated wires10, however, the present invention is not limited thereto. The core5may comprise a single insulated wire10, and may comprise two or more pieces of the insulated wires10.

For example, the conductor12composing the insulated wire10may comprise a wire conductor comprising tinned (Sn-plated) soft copper (e.g., a conductor cross section (SQ)=3 mm2). The conductor12may comprise a single wire conductor, or a strand wire comprising a plurality of the wire conductors stranded with each other. Further, the conductor12may comprise a metal wire such as a soft copper wire, a silver-plated soft copper wire, and a tinned copper alloy wire.

The insulating layer14covering the conductor12may comprise, for example, a cross-linked polyethylene (XLPE) that is an insulating material and has a thickness of 0.7 mm. The insulating layer14may comprise a resin material such as polyethylene, foam polyethylene, cross-linked foam polyethylene, polypropylene, and fluorine resin.

The core5may comprise a single insulated wire10or a plurality of insulated wires10. When forming the core5from the plurality of insulated wires10, the core5may comprise a strand wire formed by stranding the plurality of insulated wires10into a bundle. Further, a binding layer using a tape may be provided at the outer periphery of the insulated wire10. When forming the core5from the plurality of insulated wires10, the core5may further comprise a filler layer having elasticity between a binding layer of one of the insulated wires10and binding layers of other insulated wires10. When the filler layer is provided, it is possible to easily keep the cross section of the core5substantially circular. Herein, as the tape for the binding layer, a paper tape may be used. The filler layer may comprise a fiber, a resin material or the like.

According to the intended use of the cable1, a cross sectional diameter of the insulated wire10and the number of the insulated wires10may be determined. In addition, when the core5comprises the plurality of insulated wires10, it is determined according to the intended use of the cable1as to whether or not the plurality of insulated wires10should be stranded with each other.

The shield layer20may comprise a tinsel-copper in which a copper foil is provided around a core comprising a fiber or a string. To be concrete, the shield layer20comprises a braid structure formed by braiding a plurality of tinsel-coppers. Further, the shield layer20may have a wrap structure, in which the tinsel-coppers are spirally wound around the core5. In the first preferred embodiment, the “fiber” has a micro filament configuration, and the “string” has a linear sequence of the fiber.

The core of the tinsel-copper may comprise the fiber or string of a polymer resin material, by way of example only, a core string comprising a polyethylene terephthalate (PET) having a diameter of φ 0.11 mm. The core string may comprise a single fiber or string. Alternatively, the core string may be formed by braiding a plurality of fibers or strings. The copper foil may have, for example, a thickness of 12 μm. The tinsel-copper is formed by spirally winding the copper foil around an outer periphery of the core string.

Further, the tinsel-copper may be provided with a plating film on its surface. By providing the plating film on the surface of the tinsel-copper, it is possible to prevent the surface of the copper foil from oxidation. The plating film may be formed for example by tinning. By preventing the oxidation of the surface of the copper foil, it is possible to suppress a problem, for example, an increase in resistance of the shield layer20.

The reinforcing layer30is formed by braiding a plurality of fibers or strings. The fiber or string may comprise, for example, a polyvinyl alcohol having a diameter of φ 0.1 mm. Further, it is preferable that the fiber or string comprises a material that is excellent in fatigue resistance property and abrasion resistance property. By way of example only, the fiber or string may comprise at least one material selected from a group comprising polyvinyl alcohol, polyethylene terephthalate, and polyethylene-2,6-naphthalate. The fiber or string composing the reinforcing layer30preferably comprises the polyvinyl alcohol.

The sheath40is provided to cover an outer periphery of the reinforcing layer30. The sheath40comprises an insulating material. By way of example only, the sheath40may comprise a rubber material such as ethylene-propylene-diene rubber having a thickness of about 0.5 mm. Further, it is preferable that the rubber material composing the sheath40comprises a rubber material showing excellent heat resistance property, antiweatherability, and oil resistance property. As an example, a rubber material for a brake hose may be used.

As the rubber material for a brake hose, ethylene-α-olefin-polyene copolymer comprising a polyene, which is a norbornene compound containing a vinyl group at terminal, may be used. Further, as the rubber material, a rubber material including the ethylene-α-olefin-polyene copolymer comprising the polyene that is the norbornene compound containing the vinyl group at terminal, and a SiH radical-containing compound comprising a plurality of SiH radicals in one molecular (hereinafter, referred to as “blended rubber material”) may be used. In addition, as long as the blended rubber material fulfills a function for the sheath40, the blended rubber material may contain an agent such as reinforcing agent, filler, plasticizer, tenderizer, processing aid, activator, scorch-retarder, and age resistor appropriately. Further, the blended rubber material may be formed by blending different polymer materials.

As the rubber material, ethylene-propylene-diene rubber, styrene-butadiene rubber, butyl rubber, nitrile rubber or chloroprene rubber may be used. Namely, the rubber material may comprise at least one material selected from a group comprising ethylene-propylene-diene rubber, styrene-butadiene rubber, butyl rubber, nitrile rubber, and chloroprene rubber. In this preferred embodiment, it is preferable to use a blended rubber material that can be vulcanized under no pressure as the rubber material. Herein, the ethylene-α-olefin-polyene copolymer composing the blended rubber material is a polymer of ternary or more, which comprises ethylene, α-olefin, and polyene. As an example, the ethylene-propylene-diene rubber (EPDM) may be used.

For example, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene or the like may be used as the α-olefin. Furthermore, dicyclopentadiene, 1,4-hexadiene, 3-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 7-methyl-1,6-octadiene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-vinyl-2-norbornene or the like may be used as the polyene represented by dienes.

The SiH radical-containing compound composing the blended rubber material is used as a crosslinking agent for the blended rubber material. In this preferred embodiment, it is preferable to use the SiH radical-containing compound comprising at least two SiH radicals in one molecule, more preferably three SiH radicals in one molecule for the purpose of improving a degree of crosslinking. In addition, the blended rubber materials may further contain a catalyst, a reaction inhibitor or the like. As the catalyst, a catalyst for promoting hydrosilylation retroaction between the ethylene-α-olefin-polyene copolymer and the SiH radical-containing compound is used. By way of example only, a catalyst such as platinum system catalyst, palladium system catalyst, rhodium stem catalyst or the like may be used.

In addition, the reaction inhibitor may be doped appropriately to the blended rubber material for the purpose of suppressing an excessive hydrosilylation retroaction. By way of example only, benzotriazol, hydroperoxide, ethynylcyclohexanol, tetramethylethylenediamine, triarylcyanurate, acrylonitrile, acrylmaleate or the like may be used as the reaction inhibiter.

A cable comprising a core5comprising at least one insulated wire10to be used as a signal line for transmitting signals, a shield layer20provided at an outer periphery of the core5, a reinforcing layer30provided at an outer periphery of the shield layer20, and a sheath40provided at an outer periphery of the reinforcing layer30may be used as a signal cable.

Further, a cable comprising a core5comprising at least two insulated wires10to be used as electric power lines for feeding an electric power, a shield layer20provided at an outer periphery of the core5, a reinforcing layer30provided at an outer periphery of the shield layer20, and a sheath40provided at an outer periphery of the reinforcing layer30may be used as an electric power cable.

The signal cable and the electric power cable may be used together, for example, by juxtaposing the signal cable and the electric power cable.

Advantages of the Preferred Embodiment

The cable1in this preferred embodiment can be used as a cable for signal supply and/or power supply for electric and electronic components installed in a vehicle. The cable1used for the electric and electronic components installed in a vehicle is used in a tough environment, in which the flexion (bending) is frequent and large oscillations are applied.

The cable1in this preferred embodiment comprises the shield layer20for covering the core5as well as the reinforcing layer30provided between the shield layer20and the sheath40. Therefore, even though the cable1is disposed between the body of the vehicle and the part beneath the spring of the vehicle, the tinsel-copper composing the shield layer20will not be broken or disconnected because of the flexion of the cable1due to the up-and-down movement of the wheels and the torsion applied to the cable1at the time of steering of the wheels. Therefore, the cable1in this preferred embodiment is superior in the shielding performance and the tensile strength, and shows excellent flex resistance property and reliability.

Further, according to the cable1in this preferred embodiment, it is possible to suppress the disconnection of the tinsel-coppers even in the case that a large number of flexions occur, thereby suppressing a short-circuit caused by the broken tinsel-copper which breaks through the insulating layer14and electrically contacts the conductor12.

According to this structure, the cable1in this preferred embodiment has excellent tensile strength, heat resistance property, damage resistance property, waterproof property (antiweatherability) and oil resistance property, as well as extremely high reliability.

Example

FIG. 2Ais a perspective view of a cable in an Example according to the invention, andFIG. 2Bis a lateral cross sectional view along B-B of the cable shown inFIG. 2A.

A cable1ain the Example comprises a core5comprising three pieces of insulated wire10, the insulated wire10comprising a linear conductor12and an insulating layer14which covers an outer periphery of the conductor12, a shield layer20provided at an outer periphery of the core5, which is formed by braiding tinsel-coppers, each of the tinsel-coppers comprising a core string comprising a fiber and a copper foil spirally wound around an outer periphery of the core string, a reinforcing layer30provided at an outer periphery of the shield layer20and having a braid structure formed by braiding a plurality of fibers, and a sheath40provided at an outer periphery of the reinforcing layer30.

The conductor12was made by stranding602pieces of Sn-plated copper alloy wire having a diameter of φ 0.08 mm. The insulating layer14which covers the outer periphery of the conductor12was made of polytetrafluoroethylene copolymer which is a fluororesin and having a thickness of 0.5 mm. The core5was formed by stranding three pieces of the insulated wires10. In the Example, a paper tape was wound around the outer periphery of the insulated wire10as a binding layer. Further, a filler layer comprising a fiber was provided between respective insulated wires10, thereby providing the core5with a substantially circular cross section.

The shield layer20was formed by braiding the tinsel-coppers to have a braid structure. The tinsel-copper was formed by preparing a single string comprising PET as a core string and covering the outer periphery of the core string with a copper foil with a thickness of 12 μm. Herein, a diameter of the tinsel-copper is φ 0.11 mm. The reinforcing layer30was formed by braiding a plurality of fibers each having a diameter of φ 0.1 mm. The fiber was made of polyvinyl alcohol. Further, the sheath40was made of ethylene-propylene-diene rubber with a thickness of 0.5 mm.

Comparative Example 1

FIG. 3Ais a perspective view of a cable in a Comparative example 1, andFIG. 3Bis a lateral cross sectional view along C-C of the cable shown inFIG. 3A.

A cable2in the Comparative example 1 is similar to the cable1ain the Example, except that no reinforcing layer30is provided and a structure of the shield layer is different. Therefore, detailed description thereof is omitted except dissimilarities.

The cable2comprises a core5comprising three pieces of insulated wire10, the insulated wire10comprising a linear conductor12and an insulating layer14which covers an outer periphery of the conductor12, a braid shield layer21provided at an outer periphery of the core5, the braid shield layer21being formed by braiding copper wires that are metal wires, and a sheath40provided at an outer periphery of the braid shield layer21.

The braid shield layer21was formed to have a braid structure in which the copper wires each having a diameter of φ 0.11 mm are braided. The sheath40was made of the ethylene-propylene-diene rubber to have a thickness of 0.5 mm.

Comparative Example 2

FIG. 4Ais a perspective view of a cable in a Comparative example 2, andFIG. 4Bis a lateral cross sectional view along D-D of the cable shown inFIG. 4A.

A cable3in the Comparative example 2 is similar to the cable1ain the Example, except that no reinforcing layer30is provided and a structure of the shield layer is different. Therefore, detailed description thereof is omitted except dissimilarities.

The cable3comprises a core5comprising three pieces of insulated wire10, the insulated wire10comprising a linear conductor12and an insulating layer14which covers an outer periphery of the conductor12, a wrap shield layer (also called as “spiral shield layer” or “served shield layer”)22provided at an outer periphery of the core5, the wrap shield layer22being formed by spirally winding a copper wire around the outer periphery of the core5, and a sheath40provided at an outer periphery of the wrap shield layer22.

The wrap shield layer22was formed by spirally winding a copper wire or copper wires each having a diameter of φ 0.11 mm. The sheath40was made of the ethylene-propylene-diene rubber to have a thickness of 0.5 mm.

Comparative Example 3

FIG. 5Ais a perspective view of a cable in a Comparative example 3, andFIG. 5Bis a lateral cross sectional view along E-E of the cable shown inFIG. 5A.

A cable4in the Comparative example 3 is similar to the cable1ain the Example, except that a positional relationship between the reinforcing layer30and the shield layer20is different. Therefore, detailed description thereof is omitted except dissimilarities.

A cable4in the Comparative example 3 comprises a core5comprising three pieces of insulated wire10, the insulated wire10comprising a wire conductor12and an insulating layer14which covers an outer periphery of the conductor12, a reinforcing layer30provided at an outer periphery of the core5and having a braid structure formed by braiding a plurality of fibers, a shield layer20provided at an outer periphery of the reinforcing layer30, the shield layer20being formed by braiding tinsel-coppers, each of the tinsel-coppers comprising a core string comprising a fiber and a copper foil spirally wound around an outer periphery of the core string, and a sheath40provided at an outer periphery of the shield layer20.

Comparison Between the Example and the Comparative Examples 1 to 3

Performance of the cable1ain the Example was compared with performance of the cables2to4in the Comparative examples 1 to 3. The performance was compared by carrying out following evaluation tests.

(1) Flex Resistance Property Test

The cable was bent by an angle of 180° in left and right directions for plural times, a bending radius R was 30 mm (R30), and presence of disconnection of the shield layer was observed.

(2) Torsion Durability Test

Torsion of ±0.3°/mm was applied for plural times as torsional deformation, and the presence of disconnection of the shield layer was observed.

(3) Cable Tensile Property Test

A load was applied to the cable in a longitudinal direction of the cable, and the load which caused the disconnection of the cable was measured.

TABLE 1 shows a result of the evaluation tests for the respective cables in the Example and the Comparative examples 1 to 3.

Referring to TABLE 1, it is confirmed that the cable1ain the Example is excellent in flex durability (namely, flex resistance property), torsion durability, and tensile property. While the tensile property of the cable1ain the Example was 1000N or more, the tensile property of the cable4in the Comparative example 3 was 200N or less. In the cable4in the Comparative example 3, an order of forming the shield layer20and the reinforcing layer30was reversed compared with the order of forming the shield layer20and the reinforcing layer30in the cable1ain the Example 1. Therefore, the reasons of the improvement in the tensile property in the cable1ain the Example are assumed as follows. In the cable1ain the Example, the reinforcing layer30and the sheath40contact with each other, so that an adhesion between the reinforcing layer30and the sheath40is improved. Further, the tensile property is improved by forming the reinforcing layer30by braiding the tinsel-coppers.

As described above, it is confirmed that it is possible to provide the cable with excellent flex resistance property, tensile strength and reliability according to the present invention. In other words, it is possible to improve the flex resistance property, tensile strength and reliability by providing the cable1ain the Example, in which the core5comprising the insulated wires10is covered with the shield layer20, and the reinforcing layer30and the sheath40are provided in this order on the outer periphery of the shield layer20.