JP7339042B2 - Differential transmission cable and wire harness - Google Patents

Description

The present invention relates to differential transmission cables and wire harnesses.

Conventionally, a two-core differential transmission cable is used as a communication cable for automobiles. A differential transmission cable is used for Ethernet (registered trademark) communication, for example, and is required to strictly control the characteristic impedance.

Such a differential transmission cable includes, for example, a twisted pair wire in which an insulated wire composed of a conductor having a tensile strength of 400 MPa or more and an insulating coating covering the outer circumference of the conductor is twisted in a pair, and a twisted pair wire. A device including a sheath that covers the outer periphery has been proposed (see, for example, Patent Document 1). According to this differential transmission cable, since the conductor has a high tensile strength of 400 MPa or more, it is possible to secure a predetermined breaking strength required as an electric wire.

Japanese Patent No. 6108057

However, the differential transmission cable described in Patent Document 1 has high rigidity because it uses conductors with a tensile strength of 400 MPa or more. It becomes inferior.

In addition, the differential transmission cable described in Patent Document 1 needs to secure a conductor cross-sectional area of at least a certain level in order to obtain the necessary strength, which limits the reduction in diameter and weight. .

The present invention was made in order to solve such conventional problems, and its object is to achieve a smaller diameter, lighter weight, and more flexible differential gear while ensuring a predetermined breaking strength. It is to provide a transmission cable and wire harness.

The present invention is a differential transmission cable comprising a twisted wire made by twisting a pair of wires having a plurality of conductors and an insulator covering the plurality of conductors, and a sheath covering the twisted wire. is. This differential transmission cable is provided at the center of the plurality of conductors and has a tension member having a tensile strength of 800 MPa or more and 3000 MPa or less and having a tensile strength higher than that of the plurality of conductors. is 3.8 or less, and the dielectric loss tangent is 4.0×10 ⁻³ or less .

Moreover, the wire harness which concerns on this invention is equipped with said differential transmission cable.

According to the present invention, a tension member having a tensile strength of 800 MPa or more and having a tensile strength higher than that of a plurality of conductors is provided. A predetermined breaking strength can be secured. As a result, it is possible to provide a differential transmission cable that is made thinner, lighter, and more flexible while ensuring a predetermined breaking strength.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows an example of the wire harness containing the differential transmission cable which concerns on embodiment of this invention. FIG. 2 is a side view showing the differential transmission cable shown in FIG. 1; 1 is a schematic diagram showing differential transmission cables according to Examples 1 to 3 and Comparative Examples 1 and 2; FIG. 4 is a graph showing characteristics of differential transmission cables according to Examples 1 and 2, showing characteristic impedance; 4 is a graph showing characteristics of differential transmission cables according to Examples 1 and 2, showing insertion loss according to frequency.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below along with preferred embodiments. It should be noted that the present invention is not limited to the embodiments described below, and can be modified as appropriate without departing from the gist of the present invention. In addition, in the embodiments shown below, there are places where illustrations and explanations of some configurations are omitted, but the details of the omitted technologies are as long as there is no contradiction with the contents explained below. Needless to say, well-known or well-known techniques are applied as appropriate.

FIG. 1 is a cross-sectional view showing an example of a wire harness including a differential transmission cable according to an embodiment of the invention. 2 is a side view showing the differential transmission cable shown in FIG. 1. FIG.

As shown in FIG. 1, the wire harness WH according to the present embodiment is a bundle of a plurality of electric wires W, and at least one of the plurality of electric wires W (one circuit) is a differential transmission signal, which will be described in detail below. It is composed of a cable 1 .

Such a wire harness WH may be provided with connectors (not shown) at both ends of a plurality of electric wires W, for example, and a tape (not shown) may be wound to bundle the plurality of electric wires W. good too. Moreover, the wire harness WH may be provided with an exterior component (not shown) such as a corrugated tube.

A differential transmission cable 1 includes a twisted wire TW and a sheath 20 . The twist front TW is a pair of wires 10 twisted together (that is, two wires 10), and each wire 10 has a plurality of conductors 11b and an insulator 12. FIG.

The plurality of conductors 11b are composed of, for example, an annealed copper wire, a tin-plated annealed copper wire, a silver-plated annealed copper wire, or the like. The conductor 11b may be a single wire or a twisted wire. Such multiple conductors 11b preferably have a tensile strength of less than 400 MPa. The number of conductors 11b is, for example, four or more, and six in the example shown in FIG.

The insulator 12 is a covering member that covers the periphery of the plurality of conductors 11b, and is made of, for example, PE (Polyethylene), PP (Polypropylene), or foamed PE and PP.

The sheath 20 is an insulating member that covers the twisted wire TW, and is made of, for example, polyolefin. In this embodiment, the sheath 20 has a structure that is entirely filled except for the space S between the two cables 10, for example. The sheath 20 is not limited to this, and may be a cylindrical tube or the like.

Furthermore, each electric wire 10 according to this embodiment is provided with a tension member 11a. The tension member 11a is provided at the center position of the plurality of conductors 11b, and is made of a member having a tensile strength higher than that of the plurality of conductors 11b. Specifically, the tension member 11a is made of polyarylate fiber or glass fiber, and has a tensile strength of 800 MPa or more. The tension member 11a is not limited to polyarylate fiber or glass fiber.

Since the differential transmission cable 1 according to the present embodiment includes such a tension member 11a, a predetermined breaking strength is ensured without using a metal with high tensile strength for the conductor 11b or increasing the conductor cross-sectional area. can do.

In particular, since the cross-sectional area of the conductor 11b can be suppressed, the cross-sectional area (uncompressed cross-sectional area) of the inner structure 11 consisting of the tension member 11a and the plurality of conductors 11b is 0.22 mm ² or less (for example, 0.13 mm ² ), the required breaking strength can be secured (furthermore, the required breaking strength can be achieved even if a metal having a tensile strength of less than 400 MPa is used for the conductor 11b).

Specifically, for example, when the wire diameter of each of the tension member 11a (e.g., tensile strength 800 MPa) and the conductor 11b (e.g., annealed copper wire 230 MPa) is 0.16 mm (wire diameter used for 0.13 sq), The total cross-sectional area of the six conductors 11b is 0.12 mm ² , and the cross-sectional area of the tension member 11a is 0.02 mm ² . Therefore, the breaking strength of the six conductors 11b is 0.12×230=27.6N, and the breaking strength of the tension member 11a is 0.02×800=16N. Since there are two wires 10 in this embodiment, the breaking strength of the two inner structures 11 is (27.6+16)×2=87.2N. Assuming that the breaking strength of the insulator 12 and the sheath 20 is 20N, the breaking strength of the differential transmission cable 1 is 87.2+20=107.2N. Therefore, the breaking strength of 100 N required for electric wires for automobiles can be achieved.

Moreover, the tension member 11a preferably has a tensile strength of 1200 MPa or more. This is because it is possible to achieve a breaking strength of 100 N or more only with the inner structure 11 .

In this case, the breaking strength of the six conductors 11b is 0.12×230=27.6N, and the breaking strength of the tension member 11a is 0.02×1200=24N. Since there are two wires 10 in this embodiment, the breaking strength of the two inner structures 11 is (27.6+24)×2=103.2N. Therefore, the breaking strength of 100 N required for electric wires for automobiles can be achieved only by the inner structure 11 .

Further, the insulator 12 according to the present embodiment preferably has a dielectric constant of 4.0 or less and a dielectric loss tangent of 4.0×10 ⁻³ or less.

When the dielectric constant is 4.0 or less, the insulator 12 does not become thicker than necessary in order to obtain a characteristic impedance of 100±10Ω. This is because they can contribute. Also, if the dielectric loss tangent is 4.0×10 ⁻³ or less, the higher the frequency of the signal to be transmitted, the smaller the dielectric loss that affects the insertion loss.

Note that the dielectric loss tangent of the sheath 20 may be made larger than that of the insulator 12 because the dielectric constant of the sheath 20 has little influence on the characteristics, and specifically, it is set to 1.0×10 ⁻³ or less.

In addition, as shown in FIG. 2 , the two wires (twisted wires TW) 10 preferably have a twist pitch of 15 to 45 times (more preferably 40 times or less) the outer diameter of the wires 10 .

This is because it is possible to reduce the possibility that stress will be applied to the center of the twist and the insulator 12 will be crushed and the characteristic impedance will be affected, such as when the twist pitch is less than 15 times. In addition, it is possible to reduce the possibility that the twist is weak and the pitch becomes unstable, such as when the twist pitch exceeds 45 times, and the mode conversion characteristics related to electrical noise radiation or resistance deteriorate.

Furthermore, it is preferable that the two wires 10 after being twisted have a length difference of 3 mm or less per meter. This is also because it is possible to reduce the possibility that the mode conversion characteristics related to electrical noise radiation or resistance are degraded.

Next, examples and comparative examples regarding the differential transmission cable 1 according to the present embodiment will be described.

FIG. 3 is a schematic diagram showing differential transmission cables according to Examples 1 to 3 and Comparative Examples 1 and 2. FIG.

As shown in FIG. 3, in the differential transmission cable according to Example 1, the tension member was made of glass fiber (breaking strength: 3000 MPa). The number of conductors was six, and each conductor was composed of an annealed copper wire (breaking strength: 230 MPa) with a wire diameter of 0.16 mm. This resulted in an outer diameter of 0.48 mm for the inner configuration. The insulator was made of crosslinked PE (relative dielectric constant: 2.3, dielectric loss tangent: 1.3×10 ⁻³ ), and the finished outer diameter of the wire was 0.83 mm. As a result of twisting two such electric wires together, the twisted outer diameter was 1.66 mm. A sheath made of polyolefin (dielectric constant 4.0, dielectric loss tangent 4.2×10 ⁻³ ) with a thickness of 0.42 mm (distance from the outside of the sheath to the portion closest to the internal structure) was provided around the twisted wire. Ta. As a result, the differential transmission cable according to Example 1 had a finished outer diameter of 2.50 mm.

Further, in the differential transmission cable according to Example 2, the tension member was made of glass fiber (breaking strength: 3000 MPa). The number of conductors was six, and each conductor was composed of an annealed copper wire (breaking strength: 230 MPa) with a wire diameter of 0.16 mm. This resulted in an outer diameter of 0.48 mm for the inner configuration. The insulator is made of PP (dielectric constant 3.8, dielectric loss tangent 4.2×10 ⁻³ ) containing 50 wt % of magnesium hydroxide as a flame retardant material, and the finished outer diameter of the wire is 0.88 mm. became. As a result of twisting two such electric wires together, the twisted outer diameter was 1.76 mm. A sheath made of polyolefin with a thickness of 0.37 mm (distance from the outside of the sheath to the portion closest to the internal structure) (relative permittivity 4.1, dielectric loss tangent 4.2×10 ⁻³ ) was placed around the two wires. was established. As a result, the differential transmission cable according to Example 2 had a finished outer diameter of 2.5 mm.

For the differential transmission cable according to Example 3, the tension member was made of carbon fiber (breaking strength: 840 MPa). The number of conductors was six, and each conductor was composed of an annealed copper wire (breaking strength: 230 MPa) with a wire diameter of 0.16 mm. This resulted in an outer diameter of 0.48 mm for the inner configuration. In addition, the insulator is made of PP containing 50 wt% of magnesium hydroxide as a flame retardant material (relative permittivity 3.8, dielectric loss tangent 4.2×10 ⁻³ ), and the finished outer diameter of the wire is 0.88 mm. As a result of twisting two such electric wires together, the twisted outer diameter was 1.76 mm. A sheath made of polyolefin with a thickness of 0.37 mm (distance from the outside of the sheath to the portion closest to the internal structure) (relative permittivity 4.1, dielectric loss tangent 4.2×10 ⁻³ ) was placed around the two wires. was established. As a result, the differential transmission cable according to Example 3 had a finished outer diameter of 2.5 mm.

The differential transmission cable according to Comparative Example 1 was configured without a tension member. Also, the number of conductors was seven, and each conductor was composed of an annealed copper wire having a wire diameter of 0.16 mm. This resulted in an outer diameter of 0.48 mm for the inner configuration. The insulator was made of cross-linked PE, and the wire finished outer diameter was 0.83 mm. As a result of twisting two such electric wires together, the twisted outer diameter was 1.66 mm. A sheath made of polyolefin and having a thickness of 0.43 mm (the distance from the outside of the sheath to the portion closest to the internal structure) was provided around the two electric wires. As a result, the differential transmission cable according to Comparative Example 1 had a finished outer diameter of 2.5 mm.

For the differential transmission cable according to Comparative Example 2, the tension member was composed of PP fiber (breaking strength of 290 MPa). Also, the number of conductors was six, and each conductor was composed of an annealed copper wire having a wire diameter of 0.16 mm. This resulted in an outer diameter of 0.48 mm for the inner configuration. The insulator was made of cross-linked PE, and the wire finished outer diameter was 0.83 mm. As a result of twisting two such electric wires together, the twisted outer diameter was 1.66 mm. A polyolefin sheath having a thickness of 0.42 mm (the distance from the outside of the sheath to the portion closest to the internal structure) was provided around the two electric wires. As a result, the differential transmission cable according to Comparative Example 2 had a finished outer diameter of 2.5 mm.

Here, since the differential transmission cables shown in Examples 1 to 3 are provided with tension members of 800 MPa or more, they meet the breaking strength of 100 N, which is computationally required for electric wires for automobiles, for example.

In contrast, the differential transmission cables shown in Comparative Examples 1 and 2 do not have tension members of 800 MPa or more. For this reason, the differential transmission cables shown in Comparative Examples 1 and 2 do not meet the breaking strength of 100 N, which is computationally required for electric wires for automobiles, for example. Here, in order to satisfy the breaking strength of 100 N for the differential transmission cables shown in Comparative Examples 1 and 2, it is necessary to increase the conductor cross-sectional area. For this reason, there arises a problem in terms of diameter reduction, weight reduction, and flexibility.

In addition, since the differential transmission cables of Examples 1 and 2 are provided with tension members having a tensile strength of 1200 MPa or more, the breaking strength of 100 N can be satisfied only by the inner structure. On the other hand, in order to achieve a breaking strength equivalent to that of Examples 1 and 2 in Example 3, the finished outer diameter of the differential transmission cable is larger than that of Examples 1 and 2.

4 and 5 are graphs showing characteristics of the differential transmission cables according to Examples 1 and 2. FIG. 4 shows characteristic impedance, and FIG. 5 shows insertion loss according to frequency.

As shown in FIG. 4, the differential transmission cables according to Examples 1 and 2 have characteristic impedances within the range of 100±10Ω (standard value). Therefore, the differential transmission cables according to Examples 1 and 2 have desired characteristic impedance.

However, the differential transmission cable according to Example 2 has a dielectric loss tangent of 4.2×10 ⁻³ . Therefore, as shown in FIG. 5, the differential transmission cable according to the second embodiment has a higher insertion loss than that of the first embodiment. In particular, the dielectric loss, which is one of the insertion losses, becomes more dependent on the dielectric loss tangent as the frequency increases. Therefore, when the first and second embodiments are compared, the higher the frequency range, the greater the difference in insertion loss between them. On the other hand, since the differential transmission cable according to Example 1 has a dielectric loss tangent of 1.3×10 ⁻³ , the dielectric loss can be suppressed, and the insertion loss is smaller than that of Example 2. The effect was remarkable in the high frequency range.

In this manner, according to the differential transmission cable 1 according to the present embodiment, the tension member 11a having a tensile strength of 800 MPa or more and having a tensile strength higher than that of the plurality of conductors 11b is provided. A predetermined breaking strength can be ensured without using a strong metal or increasing the conductor cross-sectional area. As a result, it is possible to provide a differential transmission cable 1 that is made thinner and lighter while ensuring a predetermined breaking strength, and that is made more flexible.

Moreover, since the tension member 11a has a tensile strength of 1200 MPa or more, the inner structure 11 alone can achieve a breaking strength of 100 N or more.

In addition, since the dielectric constant of the insulator 12 is 4.0 or less, the insulator 12 does not become unnecessarily thick in order to achieve a characteristic impedance of 100±10Ω, which contributes to a reduction in diameter. Moreover, since the dielectric loss tangent of the insulator 12 is 4.0×10 ⁻³ or less, the dielectric loss that affects the insertion loss can be reduced as the frequency of the signal to be transmitted increases.

In addition, since the twist pitch of the twisted wire TW is 15 times or more the outer diameter of the wire 10, stress is applied to the twist center side as if it were less than 15 times, and the insulator may be crushed and the characteristic impedance may be affected. can be reduced. In addition, since the twist pitch is 45 times or less the outer diameter of the electric wire 10, the twist is weak and the pitch becomes unstable as when it exceeds 45 times, and the mode conversion characteristics related to the radiation or resistance of electrical noise deteriorate. It is possible to reduce the possibility of being put away.

Further, according to the wire harness WH according to the present embodiment, since the differential transmission cable 1 is provided, the diameter and weight can be reduced while ensuring a predetermined breaking strength, thereby providing a more flexible wire harness WH. can do.

As described above, the present invention has been described based on the embodiments, but the present invention is not limited to the above embodiments, and may be modified without departing from the scope of the present invention. You may combine well-known techniques.

For example, although the tension member 11a is arranged at the center of the plurality of conductors 11b in this embodiment, it may not be strictly centered, and may have a certain amount of deviation within an allowable range.

Reference Signs List 1: differential transmission cable 10: electric wire 11: inner structure 11a: tension member 11b: conductor 12: insulator 20: sheath W: electric wire WH: wire harness TW: twisted electric wire

Claims (4)

A differential transmission cable comprising: a twisted wire obtained by twisting a pair of wires having a plurality of conductors and an insulator covering the plurality of conductors; and a sheath covering the twisted wire. hand,
A tension member provided at the center of the plurality of conductors and having a tensile strength of 800 MPa or more and 3000 MPa or less and having a higher tensile strength than the plurality of conductors ,
A differential transmission cable , wherein the insulator has a dielectric constant of 3.8 or less and a dielectric loss tangent of 4.0×10 ⁻³ or less . The differential transmission cable according to claim 1, wherein the tension member has a tensile strength of 1200 MPa or more. 3. The differential transmission cable according to claim 1 , wherein the twisted wire has a twist pitch of 15 to 45 times the outer diameter of the wire. A wire harness comprising the differential transmission cable according to any one of claims 1 to 3 .

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