Communication cable and wire harness

Abstract

This communication cable (1) is provided with a twisted pair wire (TW), a sheath (20), and a silicone oil layer (30). The sheath has a solid form, and includes resin that is identical to resin contained in a material constituting an insulator as a material constituting the sheath. The silicone oil layer includes silicone oil having a viscosity of 300 CS-1000 CS inclusive. The adhesion force between the twisted pair wire and the sheath is 5N or more, and is equal to or less than the value (N) of the product of the cross-sectional area (mm2) of the insulator and the tensile strength (MPa) of the insulator.

Description

Communication cables and wire harnesses

[0001] The present invention relates to a communication cable and a wire harness.

[0002] Conventionally, communication cables have been known that include a twisted pair wire in which two wire cores are twisted together and a sheath extrusion-molded to cover the twisted pair wire. Typical sheath molding methods include a tube extrusion method in which the sheath is extruded into a tubular shape, and a solid extrusion method in which the sheath is extruded so as to fill the space between the outer circumferential surface of the sheath and the outer circumferential surface of the twisted pair wire with sheath material (so-called a solid shape) without leaving any gaps (see, for example, Patent Document 1).

[0003] In communication cables manufactured by the tube extrusion method, the sheath is tubular, which creates a gap between the twisted pair wires and the sheath. As a result, the positional relationship between the sheath and the twisted pair wires is easily changed by external stress, and the transmission characteristics of the communication cable tend to be unstable. On the other hand, communication cables manufactured by the solid extrusion method do not have the above-mentioned gap, so their transmission characteristics tend to be more stable than those of communication cables manufactured by the tube extrusion method.

[0004] It is known that when a communication cable is manufactured using the same type of material for the core insulator and sheath, the overall dielectric constant and dielectric loss tangent of the cable change little in response to temperature changes in the usage environment, and good transmission characteristics can be obtained. Therefore, the manufacture of communication cables using the solid extrusion method, which uses the same type of material for the core insulator and sheath, is being considered.

[0005] Japanese Patent Application Publication No. 2022-155824

[0006] However, when a communication cable is manufactured using the solid extrusion method using the same material for the insulator and sheath of the core, the insulator material and the sheath material have similar melting points, so the insulator is heated by the extruded sheath and melts, easily causing the insulator and sheath to stick together. When this sticking occurs, it becomes difficult to peel the sheath from the core when terminating the communication cable.

[0007] One possible solution to this problem is to place a powdered release material such as talc around the twisted pair wires, but in practice it is difficult to place the powdered release material around the twisted pair wires without leaving any gaps.

[0008] An object of the present invention is to provide a communication cable and a wire harness that can achieve both stable transmission characteristics and improved terminal workability.

[0009] In a first aspect of the present invention, a communication cable comprises: a twisted pair wire having a pair of wire cores each having a conductor and an insulator covering the conductor; a sheath arranged to cover the twisted pair wire; and a silicone oil layer arranged between the twisted pair wire and the sheath, wherein the sheath has a solid form in which the space between the outer circumferential surface of the sheath and the silicone oil layer is filled with a material constituting the sheath, and the material constituting the sheath contains the same resin as the resin contained in the material constituting the insulator, the silicone oil layer contains silicone oil having a viscosity of 300 CS or more and 1000 CS or less, the adhesive force between the twisted pair wire and the sheath is 5 N or more, and the adhesive force between the twisted pair wire and the sheath is 5 N or more and the cross-sectional area (unit: mm ２ ) and the tensile strength (unit: MPa) of the insulator.

[0010] In the present invention, the "adhesion" can be measured in accordance with the test specified in ISO 19642-2.

[0011] In a second aspect of the present invention, a wire harness includes the above-described communication cable.

[0012] FIG. 1 is a cross-sectional view showing an example of a wire harness including a communication cable according to an embodiment of the present invention. FIG. 2 is a side view showing the communication cable shown in FIG. 1. FIG. 3 is a table showing the structures, materials, etc. of the communication cables according to Examples 1 to 3 and Comparative Examples 1 to 4. FIG. 4 is a graph showing the characteristic impedance of the communication cable according to Comparative Example 1. FIG. 5 is a graph showing the transmission mode conversion characteristics of the communication cable according to Comparative Example 1. FIG. 6 is a graph showing the characteristic impedance of the communication cable according to Example 1. FIG. 7 is a graph showing the transmission mode conversion characteristics of the communication cable according to Example 1. FIG. 8 is a graph showing the adhesion force for Examples 1 to 3 and Comparative Examples 2 to 4.

[0013] The present invention will be described below in accordance with preferred embodiments. However, the present invention is not limited to the embodiments shown below and can be modified as appropriate without departing from the spirit of the present invention. In the embodiments shown below, some components are omitted from illustration and description, but it goes without saying that publicly known or well-known technologies are applied as appropriate to the details of the omitted technologies within the scope of the content described below.

[0014] Fig. 1 is a cross-sectional view showing an example of a wire harness including a communication cable according to an embodiment of the present invention, Fig. 2 is a side view showing the communication cable shown in Fig. 1 .

[0015] As shown in Fig. 1 , the wire harness WH according to this embodiment includes a plurality of electric wires W. At least one of the plurality of electric wires W (in this example, one circuit on the left side in Fig. 1 ) is a communication cable 1, which will be described in detail below.

[0016] The wire harness WH may include, for example, connectors (not shown) at both ends of the plurality of electric wires W, or may include a tape (not shown) that is wrapped around the wire harness WH to bundle the plurality of electric wires W. The wire harness WH may include an exterior part (not shown) such as a corrugated tube.

[0017] The communication cable 1 includes a twisted pair wire TW and a sheath 20. As shown in Fig. 2, the twisted pair wire TW has a shape in which two wire cores 10 are twisted together. Each wire core 10 includes a conductor 11 and an insulator 12.

[0018] The conductor 11 is made of, for example, a copper alloy. In this example, the conductor 11 is made of a plurality of wires as shown in Fig. 1, but the conductor 11 may also be made of a single wire. The conductor 11 may also be made of pure copper or aluminum, or the surface of the conductor 11 may be plated with tin, silver, or the like.

[0019] The insulator 12 is a covering member disposed to cover the periphery of the plurality of conductors 11. In this example, the insulator 12 is made of PP (Polypropylene). In this example, a PP-based resin (a resin whose main component is PP) is used as the material constituting the insulator 12, but other resins such as a PE (Polyethylene)-based resin may also be used.

[0020] The sheath 20 is an insulating member disposed to surround the twisted pair wire TW. As shown in FIG. 1 , the sheath 20 is disposed on the outside of the twisted pair wire TW in a manner that fills the space between the outer circumferential surface of the sheath 20 and the silicone oil layer 30 with the material that constitutes the sheath 20 (a so-called solid form). In other words, the sheath 20 is disposed in a so-called solid state. In particular, the sheath 20 is disposed so as to fill the gap S between the pair of wire cores 10 that constitute the twisted pair wire TW. The material that constitutes the sheath 20 contains the same resin as the resin contained in the material that constitutes the insulator 12. More specifically, the resin that constitutes the sheath 20 has the same main component as the resin that constitutes the insulator 12. In this example, the insulator 12 is made of a PP-based resin, and the sheath 20 is also made of a PP-based resin. For example, the insulator 12 may be made of PP with a small amount of additives, and the sheath 20 may be made of PP with added flame retardant for protection performance.

[0021] Furthermore, the communication cable 1 includes a silicone oil layer 30. The silicone oil layer 30 is interposed between the twisted pair wire TW and the sheath 20. The viscosity of the silicone oil constituting the silicone oil layer 30 is 300 CS or more and 1000 CS or less. CS is a unit of viscosity called "Centrifugal Stokes."

[0022] In this example, the resin constituting the insulator 12 and the resin constituting the sheath 20 are made of the same resin, although their respective blends (compositions) are slightly different. In the communication cable 1 of this example, the silicone oil layer 30 is interposed between the insulator 12 and the sheath 20. Even if the insulator 12 is heated by the molded sheath 20 during extrusion molding of the sheath 20, the insulator 12 and the sheath 20 are less likely to stick together. The silicone oil layer 30 can be easily arranged uniformly and evenly on the twisted pair wire TW by using a method of immersing the twisted pair wire TW in a silicone oil bath or by spraying the twisted pair wire TW with silicone oil. The evenly distributed silicone oil layer 30 appropriately prevents the insulator 12 and the sheath 20 from sticking together.

[0023] Furthermore, by setting the viscosity of the silicone oil layer 30 to 300 CS or more and 1000 CS or less, the adhesive force between the insulator 12 and the sheath 20 can be designed to a value suitable for terminal processing when actually using the communication cable 1. Specifically, in this example, the adhesive force between the insulator 12 and the sheath 20 is 5 N or more, and the cross-sectional area of ​​the insulator (unit: mm ２ ) and the tensile strength (unit: MPa) of the insulator. However, the "cross-sectional area of ​​the insulator" is the total cross-sectional area of ​​the insulators 12 of all the wire cores 10 used in the communication cable 1. That is, in this example, the "cross-sectional area of ​​the insulator" is the total cross-sectional area of ​​the insulators 12 of two wire cores 10. Furthermore, the "adhesion strength" can be measured in accordance with the test specified in ISO19642-2. This allows the sheath 20 to be easily peeled from the insulator 12 during terminal processing of the communication cable 1, improving terminal processability.

[0024] Here, if the adhesive force is smaller than 5 N, the twisted pair wire TW is likely to be displaced so as to slide in the axial direction relative to the sheath 20 when the sheath 20 is peeled off. As a result, the length of the twisted pair wire TW exposed at the terminal of the communication cable 1 (i.e., the processing length) changes, making it difficult to properly process the terminal. On the other hand, when the adhesive force is smaller than the "cross-sectional area of ​​the insulator (unit: mm ２ If the value of the product of the tensile strength (unit: MPa) and the tensile strength (unit: N) of the insulator 12 is larger than the value of the product of the tensile strength (unit: N) and the tensile strength (unit: MPa) of the insulator 12, deformation or breakage of the insulator 12 may occur during terminal processing. As a result, it is difficult to perform terminal processing properly.

[0025] Next, examples and comparative examples relating to the communication cable 1 will be described. FIG. 3 is a table showing the structures and materials of the communication cables according to Examples 1 to 3 and Comparative Examples 1 to 4. For the sake of convenience, the following will refer to the "cross-sectional area of ​​the insulator (unit: mm ２ The product of the tensile strength of the insulator (unit: MPa) and the cross-sectional area of ​​the insulator (unit: mm ２ ) × insulator tensile strength (MPa)".

[0026] As shown in FIG. 3, in the communication cables according to Examples 1 to 3 and Comparative Examples 1 to 4, the material constituting the conductor 11 of the wire core 10 is a copper alloy, and the cross-sectional area of ​​the conductor 11 of one wire core 10 is 0.14 mm ２ The insulator 12 of the wire core 10 is made of a resin whose main component is PP, and the cross-sectional area of ​​the insulator 12 of one wire core is 0.46 mm ２ The sheath 20 is made of a resin whose main component is PP.

[0027] In Comparative Example 1, the sheath 20 was formed by the tube extrusion method, while in Examples 1 to 3 and Comparative Examples 2 to 4, the sheath 20 was formed by the solid extrusion method. The tensile strength of the insulator 12 was 55 MPa. The total cross-sectional area of ​​the insulator 12 of the two wire cores 10 was 0.92 mm ２ (= 0.46 × 2). Therefore, the cross-sectional area of ​​the insulator (mm ２ ) × insulator tensile strength (MPa) is 50.6 N in all of Examples 1 to 3 and Comparative Examples 1 to 4.

[0028] The viscosity of the silicone oil before extrusion was 100 CS in Comparative Example 2, 300 CS in Example 1, 500 CS in Example 2, 1000 CS in Example 3, 1200 CS in Comparative Example 3, and 3000 CS in Comparative Example 4. The silicone oil was a KF-96 series silicone oil manufactured by Shin-Etsu Chemical Co., Ltd. However, since there is no product with a viscosity of 1200 CS in the KF-96 series, a mixture of silicone oils with other viscosities in the same series was used in Comparative Example 3. No silicone oil was used in Comparative Example 1.

[0029] The silicone oil is heated by the sheath 20 when the sheath 20 is extruded. However, because the silicone oil is exposed to heat for a short time (e.g., about 1 second), the viscosity of the silicone oil does not change. Therefore, the viscosity of the silicone oil after extrusion molding was the same in all of Examples 1 to 3 and Comparative Examples 2 to 4.

[0030] For the communication cables 1 according to Comparative Example 1 and Example 1, the characteristic impedance (hereinafter referred to as CIDM) and the longitudinal conversion transfer loss (hereinafter referred to as LCTL), which indicate transmission characteristics, were measured before (i.e., initial values) and after clamping. In this measurement, a plastic cable tie (specifically, an Insulock tie (registered trademark)) used to attach an automotive wire harness to a vehicle body was used as the clamp. The clamp was attached to the communication cable 1 with a binding force (specifically, 10 N or more) that prevented the clamp position from changing during measurement. The clamps were attached at three locations, approximately 10 cm, approximately 70 cm, and approximately 130 cm away from the cable end of the communication cable 1. As a result, as shown in Figure 4, the values ​​of CDIM after clamping (see the dashed lines in the figure) when the horizontal axis (time) values ​​were 1 ns, 7 ns, and 13 ns were smaller than the initial value of CIDM (see the solid line in the figure) at the same time. Note that the time of approximately 10 ns shown in Figure 4 corresponds to a length of 1 m of the communication cable 1.

[0031] Fig. 4 is a graph showing the characteristic impedance of the communication cable 1 of Comparative Example 1, and Fig. 5 is a graph showing the transmission mode conversion characteristics of the communication cable of Comparative Example 1. Both the graphs of Fig. 4 and Fig. 5 also show the standard values ​​that must be satisfied.

[0032] As shown in Fig. 4, the initial value of the characteristic impedance of the communication cable 1 according to Comparative Example 1 was near 100 Ω, which was within the range of the standard value of 90 Ω to 110 Ω. However, after clamping, the tubular sheath 20 was crushed, resulting in a deterioration in transmission characteristics. Specifically, the characteristic impedance significantly decreased when the clamping time was 1 ns, 7 ns, and 13 ns. In particular, the characteristic impedance decreased to near the lower limit of the standard value when the clamping time was 1 ns.

[0033] 5, in the communication cable 1 according to Comparative Example 1, the initial value of the transmission mode conversion characteristic was equal to or less than the standard value and was within the range of the standard value. However, after clamping, the value of the transmission mode conversion characteristic became outside the range of the standard value in the frequency band of 4 MHz or less and in the frequency band around 30 MHz.

[0034] Fig. 6 is a graph showing the characteristic impedance of the communication cable 1 according to Example 1, and Fig. 7 is a graph showing the transmission mode conversion characteristics of the communication cable 1 according to Example 1. Both the graphs in Fig. 6 and Fig. 7 also show standard values ​​that must be satisfied.

[0035] As shown in Figure 6, the initial value of the characteristic impedance of the communication cable 1 according to Example 1 was approximately 100 Ω, which was within the standard range of 90 Ω to 110 Ω. Even after clamping, the characteristic impedance did not change significantly, and the transmission characteristics were maintained. This is because the sheath 20 was formed in a solid form and was not crushed by the clamp.

[0036] 7, in the communication cable 1 according to Example 1, the initial value of the transmission mode conversion characteristic was equal to or less than the standard value and was within the range of the standard value. Even after clamping, the value of the transmission mode conversion characteristic did not exceed the standard value.

[0037] From the above, it has been found that forming the sheath 20 in a solid form can stabilize the transmission characteristics.

[0038] Referring to Figure 3, for Examples 1 to 3 and Comparative Examples 2 to 4, the adhesion between the twisted pair wires TW and the sheath 20 was measured, and the terminal processability was also evaluated. The adhesion was measured in accordance with ISO 19642-2. Specifically, the contact section between the twisted pair wires TW and the sheath 20 was set to 50 mm, and the sheath 20 was hooked into a hole of a size large enough for the twisted pair wires TW to pass through, and the twisted pair wires TW were then pulled. The terminal processability was evaluated based on whether deformation (elongation, etc.) or breakage of the insulator 12 occurred and whether the twisted pair wires TW were displaced when the sheath 20 was peeled off after a cut was made in the sheath 20.

[0039] Five samples were prepared for each of Examples 1 to 3 and Comparative Examples 2 to 4, and the adhesion and terminal processability were evaluated. Figure 3 shows the average, maximum, and minimum adhesion values ​​for the five samples. For terminal processability, an "A" is indicated if all five samples exhibited good (passed) terminal processability, and a "B" is indicated if at least one of the five samples exhibited poor (failed) terminal processability. It is believed that the lowest adhesion value was obtained when the largest amount of silicone oil was applied, and the highest adhesion value was obtained when the smallest amount was applied. In both cases, the adhesion only varied within the range in which the appropriate amount of silicone oil was applied.

[0040] FIG. 8 is a graph showing the adhesion strength of Examples 1 to 3 and Comparative Examples 2 to 4.

[0041] 3 and 8, the adhesion strength in Comparative Example 2 was 51.2 N on average, with a maximum value of 58 N and a minimum value of 43 N. Of these, at least the sample with the highest adhesion strength had poor terminal processability.

[0042] The adhesion strength in Example 1 was 24.6 N on average, with a maximum value of 32 N and a minimum value of 15 N. In Example 1, all samples had good terminal processability.

[0043] The adhesive strength in Example 2 had an average value of 17.0 N, a maximum value of 24 N, and a minimum value of 12 N. In Example 2, all samples had good terminal processability.

[0044] The adhesive strength in Example 3 had an average value of 12.2 N, a maximum value of 16 N, and a minimum value of 10 N. In Example 3, all samples had good terminal processability.

[0045] The adhesive strength in Comparative Example 3 had an average value of 6.8 N, a maximum value of 10 N, and a minimum value of 3 N. Of these, at least the sample with the minimum adhesive strength had poor terminal processability.

[0046] The adhesion strength in Comparative Example 4 had an average value of 2.4 N, a maximum value of 5 N, and a minimum value of 1 N. Of these, only the sample with the highest adhesion strength had good terminal processability, and the other samples had poor terminal processability.

[0047] Here, since the sample of Comparative Example 4, which had the highest adhesion force (i.e., 5 N), had good terminal workability, it became clear that an adhesion force of 5 N or more is preferable. In order to prevent breakage or excessive elongation of the insulator 12 and improve terminal workability, the "insulator cross-sectional area (mm ２ It is preferable that the value (N) of "(N) × (tensile strength of insulator (MPa) × (tensile strength of insulator (MPa))" is not more than that. In fact, in Comparative Example 2, it was revealed that when the value calculated by the above formula (i.e., 50.6 N) was exceeded, the terminal processability became poor.

[0048] Furthermore, it was also found that if the viscosity of the silicone oil is 300 CS or more and 1000 CS or less before extrusion and is 300 CS or more and 1000 CS or less after extrusion, the above-mentioned adhesive strength is easily obtained.

[0049] As explained above, the communication cable 1 and wire harness WH according to this embodiment comprise the twisted pair wires TW and the sheath 20 provided in a solid form. This makes it difficult for the transmission characteristics to change even when an external force is applied to the communication cable 1 and wire harness WH, and allows for stabilization of the transmission characteristics. The communication cable 1 and wire harness WH comprise a silicone oil layer 30 made of silicone oil. Compared to the case where a powdered lubricant is used, the silicone oil layer 30 can be easily and evenly distributed around the twisted pair wires TW. The viscosity of the silicone oil is 300 CS or more and 1000 CS or less, and the adhesive force between the twisted pair wires TW and the sheath 20 is 5 N or more and the "insulator cross-sectional area (mm ２ ) × insulator tensile strength (MPa)" value (N) or less. This prevents the twisted pair wire TW from being displaced during terminal processing due to an excessively low adhesion, which results in poor terminal processability. Conversely, it prevents the insulator 12 from being deformed or broken during terminal processing due to an excessively high adhesion, which results in poor terminal processability. Therefore, both stabilization of transmission characteristics and improvement of terminal processability are achieved.

[0050] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be adopted within the scope of the present invention. For example, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. are possible as appropriate. Furthermore, the material, shape, dimensions, number, location, etc. of each component in the above-described embodiments are arbitrary as long as they can achieve the present invention, and are not limited thereto.

[0051] This application is based on a Japanese patent application (Patent Application No. 2024-022735) filed on February 19, 2024, the contents of which are incorporated herein by reference.

[0052] The communication cable and wire harness of the present invention can achieve both stable transmission characteristics and improved terminal processability. The present invention having this effect can be used, for example, as a communication cable or wire harness to be installed in an automobile or the like.

[0053] 1: Communication cable 10: Wire core 11: Conductor 12: Insulator 20: Sheath 30: Silicone oil layer TW: Twisted pair wire WH: Wire harness

Claims

1. A communications cable comprising: a twisted pair wire having a pair of wire cores each having a conductor and an insulator covering the conductor; a sheath arranged to cover the twisted pair wire; and a silicone oil layer arranged between the twisted pair wire and the sheath; wherein the sheath has a solid form in which the space between the outer circumferential surface of the sheath and the silicone oil layer is filled with a material constituting the sheath, and the material constituting the sheath contains the same resin as that contained in the material constituting the insulator; the silicone oil layer contains silicone oil having a viscosity of 300 CS or more and 1000 CS or less; the adhesive force between the twisted pair wire and the sheath is 5 N or more, and the adhesive force is 5 N or more when the cross-sectional area of ​​the insulator (unit: mm ２ ) and the tensile strength (unit: MPa) of the insulator, is equal to or less than the product (unit: N).

2. A wire harness comprising the communication cable according to claim 1.

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