JP2023009377A - Signal transmission cable - Google Patents

Abstract

To provide a signal transmission cable that is highly resistant to external noise.SOLUTION: A signal transmission cable includes: a center conductor; an insulator provided to surround the outer circumference of the center conductor; a shield conductor provided to surround the outer circumference of the insulator; and an outer sheath provided to surround the outer circumference of the shield conductor. The shield conductor has two layers of laterally wound conductors, that is, an inner-side laterally wound conductor and an outer-side laterally wound conductor. When setting a winding angle of the inner side laterally wound conductor with respect to the axial direction of the center conductor as θ1 and a winding angle of the outer-side laterally wound conductor as θ2, the sum of θ1 and θ2 is determined so that the mutual inductance between the inner-side laterally wound conductor and the outer-side laterally wound conductor is 0.SELECTED DRAWING: Figure 1

Description

The present invention relates to a signal transmission cable.

2. Description of the Related Art Conventionally, as a signal transmission cable, a coaxial cable having a central conductor, an insulator, a shield conductor, and a sheath is known (see Patent Document 1).

JP 2010-009835 A

However, when conventional signal transmission cables are used in an environment where electronic devices and components are densely mounted, the noise (hereafter referred to as external noise) that is applied to the signal transmission cable from the electronic devices and components There were cases where it was affected by

An object of the present invention is to provide a signal transmission cable that is highly resistant to external noise.

According to one aspect of the invention,
a center conductor;
an insulator provided to surround the outer periphery of the central conductor;
a shield conductor provided so as to surround the outer periphery of the insulator;
a jacket provided to surround the outer circumference of the shield conductor;
has
The shield conductor has two layers of horizontally wound conductors, an inner horizontally wound conductor and an outer horizontally wound conductor,
When the winding angle of the inner laterally wound conductor is θ1 and the winding angle of the outer laterally wound conductor is θ2 with respect to the axial direction of the central conductor, the sum of θ1 and θ2 is the inner laterally wound conductor. Mutual inductance with the outer laterally wound conductor is determined to be 0,
A signal transmission cable is provided.

According to the present invention, it is possible to provide a signal transmission cable that is highly resistant to external noise.

FIG. 1 is a partially enlarged perspective view of a coaxial cable 1, which is a signal transmission cable according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing a cross section obtained by cutting the coaxial cable 1 according to one embodiment of the present invention along a plane perpendicular to the longitudinal direction. FIG. 3 is an explanatory diagram schematically showing the winding angle of the shield conductor 6 according to one embodiment of the present invention.

<One embodiment of the present invention>
Configuration Example of Coaxial Cable 1 First, a configuration example of a coaxial cable 1 as a signal transmission cable according to an embodiment of the present invention will be described. As shown in FIG. 1, a coaxial cable 1 according to this embodiment includes a central conductor 2, an insulator 3, a shield conductor 6, and a sheath 7. As shown in FIG.

More specifically, as shown in FIGS. 1 and 2, a coaxial cable 1 is provided with an insulator 3 so as to surround the outer circumference of a central conductor 2, and two layers of laterally wound conductors are provided so as to surround the outer circumference. A shield conductor 6 having (an inner laterally wound conductor 4 and an outer laterally wound conductor 5) is provided, and a jacket 7 is provided so as to surround the outer periphery thereof. The central conductor 2, the insulator 3, the shield conductor 6 and the jacket 7 are coaxially formed over the entire length of the cable so that the characteristic impedance is uniform.

The central conductor 2 constitutes the core wire (also referred to as core wire) of the coaxial cable 1 . The central conductor 2 is composed of a single metal wire (single wire) or a twisted wire obtained by twisting a plurality of (for example, seven) metal wires.

In the case of a single wire, if the cross-sectional area of the conductor is the same, the diameter can be made smaller than that of the stranded wire. Twisted wires are advantageous in that they are more flexible than single wires and are less likely to break. The invention can be applied to either solid or stranded wire, depending on its application. 1 to 3 illustrate the case of using a single wire.

The central conductor 2 has a substantially circular cross-sectional shape, and is made of, for example, copper (Cu), a Cu alloy, aluminum (Al), or an Al alloy. The outer surface of the central conductor 2 may be plated with tin (Sn).

For the center conductor 2, it is preferable to use a lead wire corresponding to #30 (30 AWG) to #50 (50 AWG) of AWG (American Wire Gauge). For example, when seven 44 AWG strands with an outer diameter of 0.05 mm are twisted to form a stranded wire, the outer diameter is 0.15 mm, and the center conductor 2 equivalent to 34 AWG is constructed.

The lateral periphery of the central conductor 2 , that is, the outer periphery is covered with an insulator 3 . Although the insulator 3 is provided over the entire length of the central conductor 2 in the longitudinal direction, FIG. exemplified.

The insulator 3 is made of a fluorine resin such as crosslinked polyolefin, FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), or the like.

In order to obtain a predetermined characteristic impedance, the insulator 3 preferably has a thickness of 0.04 mm or more and an outer diameter of 0.30 mm or less and an outer diameter of 0.15 mm or more and 0.90 mm or less. .

A side periphery of the insulator 3 , that is, an outer periphery thereof is covered with a shield conductor 6 . The shield conductor 6 is composed of two layers of laterally wound conductors wound spirally, that is, an inner laterally wound conductor 4 and an outer laterally wound conductor 5 . The inner laterally-wound conductor 4 and the outer laterally-wound conductor 5 are crossed and in contact with each other, and are wound in different winding directions. The winding direction of the inner laterally wound conductor 4 and the outer laterally wound conductor 5 may be either right-handed or left-handed as long as the winding directions are different from each other. Although the shield conductor 6 is provided over the entire length of the central conductor 2 in the longitudinal direction, in FIG. A state in which the conductor 5 is removed is illustrated.

As shown in FIG. 3, the shield conductor 6 is formed by winding the inner laterally wound conductor 4 at a winding angle θ1 and the outer laterally wound conductor 5 at a winding angle θ2. The “winding angle” refers to the inclination angle of the wires of the laterally wound conductors (the inner laterally wound conductor 4 and the outer laterally wound conductor 5 ) with respect to the axial direction of the central conductor 2 . In the following description, the winding angle .theta.1 of the inner laterally wound conductor 4 is referred to as .theta.1, and the winding angle .theta.2 of the outer laterally wound conductor 5 is referred to as .theta.2.

In this embodiment, the sum of θ1 and θ2 is determined so that the mutual inductance between the inner laterally wound conductor 4 and the outer laterally wound conductor 5 is 0 (zero). In this embodiment, for example, both θ1 and θ2 can be set to a magnitude of 25° or more and 65° or less. By setting such a winding angle, in addition to making it less susceptible to external noise (that is, increasing resistance to external noise), the laterally wound conductor (inner lateral It is possible to prevent the wire strands of the wound conductor 4 and the outer laterally wound conductor 5) from coming apart, and furthermore, it is possible to reduce the production cost.

As described above, when θ1 and θ2 are set at 25° or more and 65° or less, the sum of θ1 and θ2 is 50° or more and 130° or less (50°≦θ1+θ2≦130°). Become. By setting the sum of θ1 and θ2 within such a numerical range, the mutual inductance between the inner laterally wound conductor 4 and the outer laterally wound conductor 5 can be reduced (the mutual inductance can be reduced to 0), and external noise can be reduced. can increase resistance to

The relationship between mutual inductance reduction and resistance to external noise will be described. A part of the noise current induced in the outer laterally wound conductor 5 by external noise flows through the inner laterally wound conductor 4 due to electromagnetic coupling. A noise current flowing through the inner laterally wound conductor 4 causes a potential difference between the central conductor 2 and the shield conductor 6 . If an unintended potential difference occurs between the central conductor 2 and the shield conductor 6, it may cause malfunction in signal transmission. Therefore, in order to increase the resistance to external noise, the electromagnetic coupling between the outer laterally wound conductor 5 and the inner laterally wound conductor 4 is suppressed, that is, the mutual inductance is reduced (more specifically, the mutual inductance is reduced to 0). ) is important. In the present invention, the sum of .theta.1 and .theta.2 is within the above-described predetermined range. can be made smaller. In the coaxial cable 1 (signal transmission cable) according to the present embodiment, the resistance to external noise can be increased in the frequency band of 30 GHz or less, but the resistance to external noise in the frequency band of 3 MHz or less is increased. is particularly effective.

The sum of θ1 and θ2 is preferably 80° or more and 100° or less (80°≦θ1+θ2≦100°), most preferably 90° (θ1+θ2=90°). By setting the sum of θ1 and θ2 within such a numerical range, the mutual inductance between the inner laterally wound conductor 4 and the outer laterally wound conductor 5 is further reduced (that is, the mutual inductance is set to 0). ), and the resistance to external noise can be further increased. In particular, by setting θ1+θ2=90°, the mutual inductance can be reduced to 0 (zero), so the electromagnetic coupling between the outer laterally wound conductor 5 and the inner laterally wound conductor 4 can be eliminated, and external noise resistance can be maximized. can be It should be noted that "making the mutual inductance of the inner laterally-wound conductor 4 and the outer laterally-wound conductor 5 be 0 (zero)" here means not only the case where the mutual inductance is 0, but also the range of error. Even cases where the mutual inductance can be regarded as substantially 0 (zero) are included in the scope of rights according to the present invention.

Although there is no particular limitation on the magnitude relationship between θ1 and θ2, it is preferable that θ1≧θ2. By doing so, in addition to increasing the resistance to external noise, it is possible to reliably prevent the strands of the laterally wound conductor from coming apart during terminal processing.

The wire diameters of the inner laterally wound conductor 4 and the outer laterally wound conductor 5 can be 0.001 mm or more and 0.05 mm or less and 0.01 mm or more and 0.04 mm or less, respectively. The wire diameter of the inner laterally wound conductor 4 is preferably larger than the wire diameter of the outer laterally wound conductor 5 . By doing so, the outer diameter of the shield conductor 6 can be suppressed while increasing the resistance to external noise.

The wire diameter of the transversely wound conductors (the inner transversely wound conductor 4 and the outer transversely wound conductor 5) is 0.05 to 0.09 times the diameter of the shield portion of the coaxial cable 1 (hereinafter referred to as the shield winding diameter). Preferably. By doing so, it is possible to reduce the diameter of the coaxial cable 1, improve the flexibility and bending resistance, and suppress the deterioration of shielding characteristics and attenuation. If the wire diameter of the laterally wound conductor is less than 0.05 times the shield winding diameter, it becomes difficult to secure shielding characteristics, and the resistance value of the shielding conductor 6 increases, which is disadvantageous in terms of attenuation characteristics. Further, if the wire diameter of the horizontally wound conductor exceeds 0.09 times the shield winding diameter, the wire is likely to be cut by repeated bending, which is disadvantageous in terms of mechanical reliability.

A side circumference of the shield conductor 6 , that is, an outer circumference thereof is covered with a jacket 7 . Although the jacket 7 is provided over the entire longitudinal length of the central conductor 2, FIG. exemplified.

The jacket 7 is made of, for example, FEP and PFA as well as PTFE (polytetrafluoroethylene) and ETFE (tetrafluoroethylene-ethylene copolymer). Since these fluororesins are excellent in thin-wall workability, the diameter of the coaxial cable 1 can be reduced. In addition, since these fluororesins have a low coefficient of dynamic friction, the coaxial cable 1 can be improved in bending resistance.

The outer cover 7 can be formed, for example, by extrusion molding using an extruder, and the thickness and outer diameter of the outer cover 7 are, for example, 0.02 mm or more and 0.06 mm or less, respectively, and an outer diameter of 0.25 mm or more. It is preferably 1.2 mm or less.

<Other embodiments>
Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the scope of the invention.

In the above-described embodiment, the coaxial cable 1 in which the central conductor 2 is covered with the insulator 3 is taken as an example of the signal transmission cable, but the present invention is not limited to this. For example, it is suitable for differential signal transmission cables in which a pair of conductors are collectively covered with an insulator, and differential signal transmission cables in which a plurality of insulated wires in which one conductor is covered with an insulator are arranged in parallel. can. Even in these cases, the same effects as those of the above-described embodiments can be obtained.

REFERENCE SIGNS LIST 1 signal transmission cable 2 center conductor 3 insulator 4 inner laterally wound conductor 5 outer laterally wound conductor 6 shield conductor 7 jacket

Claims (5)

a center conductor;
an insulator provided to surround the outer periphery of the central conductor;
a shield conductor provided so as to surround the outer periphery of the insulator;
a jacket provided to surround the outer circumference of the shield conductor;
has
The shield conductor has two layers of horizontally wound conductors, an inner horizontally wound conductor and an outer horizontally wound conductor,
When the winding angle of the inner laterally wound conductor is θ1 and the winding angle of the outer laterally wound conductor is θ2 with respect to the axial direction of the central conductor, the sum of θ1 and θ2 is the inner laterally wound conductor. A signal transmission cable determined to have a mutual inductance of 0 with the outer laterally wound conductor. The sum of θ1 and θ2 is 80°≦θ1+θ2≦100°,
The signal transmission cable according to claim 1. The magnitude relationship between θ1 and θ2 is θ1≧θ2.
The signal transmission cable according to claim 1 or 2. A wire diameter of the inner laterally wound conductor is larger than a wire diameter of the outer laterally wound conductor,
The signal transmission cable according to any one of claims 1 to 3. The central conductor has a conductor cross-sectional area of 0.003 mm ² to 0.09 mm ² ,
The wire diameters of the inner laterally wound conductor and the outer laterally wound conductor are 0.05 to 0.12 times the diameter of the shield portion of the cable.
A signal transmission cable according to any one of claims 1 to 4.

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