JP3072957B2 - Multi-core cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a multi-core cable for signal transmission having a relatively large conductor diameter, such as a speaker cable used for electrical connection between an amplifier of an audio equipment and a speaker. The present invention relates to a multi-core cable capable of simultaneously improving terminal workability and stabilizing electrical characteristics.

[0002]

2. Description of the Related Art For example, a multi-core cable for signal transmission having a relatively large conductor diameter, such as a speaker cable used for electrical connection between an amplifier of an audio device and a speaker, is generally provided as shown in FIG. A stranded body 14 formed by twisting a plurality of insulated wires 12 each composed of a center conductor 18 mainly composed of copper or the like and an insulator 20 provided in close contact with the center conductor 18; This twisted body 1
4 and an outer coating 16 provided thereon. The plurality of insulated wires 12 generally have a circular cross section as shown in FIG.

[0003] Such a multi-core cable 1 having a large conductor diameter.
0, for example, a speaker cable will be described as an example. In actual use, in order to connect both ends to devices such as an amplifier and a speaker, the insulator 20 of the insulated wire 12 is extended over about 20 to 30 mm. End processing for exposing the center conductor 18 by stripping is required. However, the insulator 20 is generally extruded over the center conductor 18,
In this case, since it is preferable in terms of sound quality to fix the center conductor 18 with the insulator 20, pressure is applied to the insulator 20 to be extruded to increase the degree of adhesion between the center conductor 18 and the insulator 20. 18 in the case of stranded wire-like conductor by twisting thin line, to increase the adhesion as the insulator 20 to the valley twisting enters is that Re generally performed <br/>.

For this reason, in such an insulated wire 12, since the adhesion between the center conductor 18 and the insulator 20 is high, stripping of the insulator 20 is not always easy with a commonly used hand stripper. It cannot be performed, and after making a cut in the circumferential direction of the insulator 20 with a cutter, FIG.
As shown in the figure, it is necessary to cut a plurality of vertical slits in the longitudinal direction of the insulator 20 by using the same cutter, and finally peel off the insulator 20 so as to peel the banana skin.

[0005]

In this case, in the multi-core cable 10 shown in FIG. 8 using a general insulated wire 12 having a circular cross section, the insulator 20 is made of FEP, P
When formed of a relatively hard resin such as a fluororesin such as FA, polypropylene, high-density polyethylene, and semi-hard polyvinyl chloride, the adhesive strength between the center conductor 18 and the insulator 20 is high, and Since the cutter 20 is hard, it is necessary to press the cutter blade 28 against the insulator 20 with a strong force. If the force is too strong, the center conductor 18 may be damaged or each of the stranded wires constituting the center conductor 18 may be damaged. The wire may be cut. Also, in order to make a vertical split in the longitudinal direction of the insulator 20, it is necessary to move the cutter blade 28 in the longitudinal direction of the insulator 20, but the cutter blade 28
Since there is no guide for guiding the blade, it is difficult to linearly move the blade 28 of the cutter, for example, by deflecting the blade 28 of the cutter. On the other hand, even when the insulator 20 is formed of a relatively flexible material such as a vinyl chloride resin or a rubber material, the insulator 20 adheres to the cutter blade 28, so that the cutter blade 28 is not necessarily moved as desired. Can not be
Similarly, the center conductor 18 may be damaged. As described above, the general multi-core cable 10 has a drawback that the workability at the time of terminal processing for stripping the insulator 20 and exposing the center conductor 18 is low.

In order to avoid such a disadvantage, as shown in FIG. 9, a multi-core cable 10 using an insulated wire 12 in which a grooved bottomed slit 24 extending in a longitudinal direction is formed in an insulator 20 is provided. It is possible. According to this, at the groove bottom 24A of the bottomed grooved slit 24, the insulator 2
Since the thickness of 0 is thin, even if the insulator 20 is hard, the force for pressing the cutter blade 28 is small, and the groove 24 with the bottom makes it easy to insert the cutter blade 28 into the insulator 20. Since the bottom groove-like slit 24 serves as a guide when the blade 28 of the cutter moves, it is easy to appropriately move the blade 28 of the cutter, the end workability is improved, and the center conductor 18 is prevented from being damaged. be able to.

As described above, when the grooved slit 24 with the bottom is provided in the insulator 20, the end workability is improved, but the cross-sectional area of the center conductor 18 and the cross-sectional area of the insulated wire 12 including the insulator 20 are large. When the insulator 20 is formed of a relatively flexible material such as the above-mentioned vinyl chloride resin or the like, as shown in FIG. The insulator 12 is deformed by compression or the like at the portion of the bottomed grooved slit 24 due to the force applied to the insulated wire 12 at the time of twisting.
If they overlap, a plurality of insulated wires 1
The space between the two center conductors 18 may be small. As described above, in the portion where the interval between the center conductors 18 is reduced, the outer surface of the insulated wire 12 is dented and the characteristic impedance fluctuates at the same time. For this reason, the stability of the electrical characteristics in the longitudinal direction of the multi-core cable 10 decreases,
Problems such as a signal reflection phenomenon and pulse fluctuation occur in a pulse signal. Such a problem causes deterioration of sound quality particularly in an audio cable such as a speaker cable, and in a cable for transmitting an image signal,
There are drawbacks that appear as a reduction in resolution and a lack of subtle expression.

[0008] An object of the present invention is to provide a multi-core cable having good terminal workability and stable electric characteristics in order to avoid the above-mentioned drawbacks.

[0009]

According to the present invention, as a means for solving the above-mentioned problems, a plurality of insulated wires each comprising a center conductor and an insulator provided in close contact with the center conductor are interconnected. A multi-core cable having at least one grooved bottomed slit extending in the longitudinal direction thereof, comprising a stranded body formed by twisting the stranded body and an outer coating provided on the stranded body. In this insulator,
A multi-core cable having a convex portion formed to extend in a longitudinal direction along an outer edge of at least one groove wall of a bottomed grooved slit and protruding from an outer surface of an insulator. is there.

[0010]

As described above, when the bottomed grooved slit is provided on the insulator and the protrusion is formed so as to extend in the longitudinal direction along the outer edge of the bottomed grooved slit, the bottomed grooved slit is formed. At the bottom of the groove, the thickness of the insulator is relatively thin, so the pressing force on the cutter blade is small, and
The bottomed grooved slit makes it easier to insert the blade of the cutter, and the bottomed grooved slit serves as a guide when the blade of the cutter is moved. The terminal can be easily processed without damaging the terminal. At the same time, by improving the terminal workability in this way, the insulator can be formed from a relatively hard material capable of obtaining high-resolution sound quality, and these insulated wires are twisted and twisted. In the case of a body, the material of the insulator is hard, so the bottomed grooved slit is not easily deformed,
In addition, even when the bottomed grooved slits of a plurality of insulated wires overlap each other, the thickness of the protruding portion can prevent the interval between the center conductors of the plurality of insulated wires from becoming unnecessarily small. In addition, stabilization of electrical characteristics can be realized.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a multi-core cable 10 according to the present invention, wherein the multi-core cable 10 comprises a plurality, in the illustrated embodiment, two cables. Body 14 formed by twisting the insulated wires 12 of each other, and the outer covering 1 provided on the twisted body 14
It consists of six.

As shown in FIGS. 1 and 2, each of the two insulated wires 14 includes a center conductor 18 and an insulator 20 provided on and in close contact with the center conductor 18.
The center conductor 18 is formed of an appropriate conductor such as a single wire or a stranded wire made of a single-crystal high-purity copper wire or a high-purity oxygen-free copper wire, and when used as a speaker cable or the like, usually has a low sound quality. In order to prevent deterioration, the cross-sectional area should be 0.
75 mm or more, and the conductor outer diameter is set to about 1 mm or more.

The material of the insulator 20 may be a thermoplastic resin such as a fluororesin, polyethylene, polypropylene, polyvinyl chloride, or the like, in view of signal transmission characteristics and sound quality.
Admixtures containing these as the main components, as well as stable insulating properties such as rubbers such as silicone rubber and butyl rubber, in addition to crosslinked resins obtained by subjecting these thermoplastic resins to crosslinking using an electron beam or the like. A material having moldability can be used.

The insulator 20 is provided in close contact with the center conductor 18 by extrusion coating on the center conductor 18. In this case, if the center conductor 18 is fixed with the insulator 20, good sound quality can be obtained. Therefore, pressure is applied to the insulator 20 to be coated by extrusion, and the degree of adhesion between the center conductor 18 and the insulator 20 is increased. In particular, when the center conductor 18 is a stranded conductor in which fine wires are twisted, it is preferable to increase the adhesion by inserting the insulator 20 into the valley of the twist. The insulator 20 is formed to cover the entire length of the center conductor 18 as shown in FIG.

The outer coating 16 is, in the embodiment shown,
As shown in FIG.
In order to prevent the influence of extraneous noise, this sheath 22
And a shield (not shown) provided between the twisted body 14 and the sheath 22, or a suitable press-winding may be applied thereto.

In the multicore cable 10 of the present invention, the insulator 20 of the insulated wire 12 has a grooved bottomed groove 24 extending in the longitudinal direction of the insulator 20, as shown in FIG. In the illustrated embodiment, two bottomed grooved slits 24 are provided at opposite positions at 180 ° intervals in the circumferential direction of the insulated wire 12. As shown in FIG. 2, these bottomed grooved slits 24 are formed with a groove bottom 24A,
Two groove walls 24B located on the left and right of the groove bottom 24A,
24C, and between the groove walls 24B and 24C, a blade 2 of a cutter described later is provided.
An opening 27 into which the hole 8 is inserted is formed.

As described above, when the grooved bottomed slit 24 is formed in the insulator 20, the workability of the terminal processing for forming the strip by exposing the center conductor 18 shown in FIG. 6 is improved.
That is, first, since the bottomed grooved slit 24 forms the opening 27 in the insulator 20, the opening 27 makes it easier to insert the cutter blade 28 into the bottomed grooved slit 24.
Further, in this case, the groove bottom 24 of the bottomed grooved slit 24 is formed.
Since the thickness Tb (see FIG. 2) of the insulator 20 at A is relatively thin, the force for pressing the cutter blade 28 is small. Further, the bottomed grooved slit 24 serves as a guide for guiding the movement of the blade 28 of the cutter.
A along the boundary line 24D between the groove walls 24B and 24C, and the surface of the blade 28 of the cutter is moved along the groove walls 24B and 24C.
Since the blade 28 of the cutter can be moved while following C, the blade 28 of the cutter can be moved linearly and appropriately.

Further, since the terminal can be easily processed in this manner, the center conductor 18 is not damaged when the insulator 20 is cut vertically. Not only relatively soft materials such as vinyl resin and rubber materials, but also conventional materials are said to have low end workability because of their rigidity. Fluororesins such as FEP and PFA, polypropylene, high-density polyethylene, semi-rigid Polyvinyl chloride or the like can also be used. In this case, in particular,
A relatively hard material such as polypropylene is advantageous in obtaining high-resolution sound quality, and even when the twisted body 14 is used, the insulator 20 is compressed and deformed at the portion of the bottomed grooved slit 24 so that the center can be formed. It is very advantageous that the use of these materials does not need to be limited in relation to the terminal workability, because it is advantageous in preventing the spacing between the conductors 18 from becoming unnecessarily small. Therefore, in practice, it is desirable to form the insulator 20 from these preferable hard materials as much as possible.

As shown in FIGS. 2 and 3, the multi-core cable 10 of the present invention extends in the longitudinal direction along the outer edge 25 of one groove wall 24C of the bottomed grooved slit 24 of the insulator 20. It has a projection 26 formed and protruding from the outer surface of the insulator 20.

As shown in FIG. 2, the convex portion 26 has a curved shape (kamaboko shape) so as to protrude outward from the other outer peripheral surface of the insulator 20 which is substantially concentric with the center conductor 18. It is formed. Therefore, the cross section of the insulator 20 is not circular, and in the portion having the convex portion 26, as shown in FIG. 2, the thickness Tt of the convex portion 26 (the maximum thickness of the convex portion 26:
2), the thickness T of the insulator 20 in the other part.
(See FIG. 2).
b: See FIG. 2).

For this reason, as shown in FIG.
4, the bottomed grooved slits 2 of the plurality of insulated wires 12
Even in the portion where the four wires 4 overlap, the protrusions 26 abut against each other's insulators 20 and the interval between the center conductors 18 of the two insulated wires 12 does not become smaller than necessary. In this case, in particular, even if a force is applied to the insulated wire 12 at the time of twisting and the insulator 20 is compressed, there is a margin by the thickness Tt of the convex portion 26 (see FIG. 2), so that the space between the two center conductors 18 Can be prevented from becoming smaller than necessary. For this reason, the characteristic impedance does not fluctuate, signal reflection phenomena, pulse fluctuations, and the like do not occur, and it is possible to prevent the electrical characteristics in the longitudinal direction of the multicore cable 10 from becoming unstable, thereby achieving stable operation. Electrical characteristics can be maintained. Therefore, particularly when the multi-core cable 10 is a speaker cable or a cable for transmitting an image signal, deterioration of sound quality, reduction of resolution,
Further, it is possible to effectively prevent the occurrence of a subtle lack of expression.

As shown in FIG. 2, the projection 26 must be formed so as to extend in the longitudinal direction along the outer edges 25 of the groove walls 24B and 24C of the bottomed grooved slit 24. As shown in FIG. 1, in the stranded body 14, there is a possibility that a problem that the interval between the center conductors 18 becomes small particularly in a portion where the bottomed grooved slits 24 of the plurality of insulated wires 12 overlap each other. This is to prevent this effectively. However, if it is possible to prevent the interval between the center conductors 18 of the twisted body 14 from being reduced, the protrusion 26
It is not always necessary to be continuous over the entire length of the bottomed grooved slit 24, and for example, it may be provided intermittently in the longitudinal direction.

These bottomed grooved slits 24 and projections 26
Is extruded with an extrusion die (not shown) having a shape corresponding to the grooved slit 24 and the convex portion 26 with a bottom,
Alternatively, after forming the insulator 20 into a cylindrical shape slightly larger than a predetermined shape, the insulator 20 can be formed by cutting. In this case, considering that the convex portion 26 is easy to form, it is preferable to form the convex portion 26 integrally with the insulator 20 as described above. It may be attached to the body 20 by fusion or the like.

Since the multi-core cable 10 is used after being cut to an appropriate length according to need, these multi-core cables 10 are used so that good end workability can be ensured no matter where they are cut. As shown in FIG. 3, it is desirable that the bottom groove-shaped slit 24 and the convex portion 26 be formed continuously over the entire length of the insulated wire 12.

Next, another embodiment of the present invention will be described with reference to FIG.
5 and FIG. 5, in this embodiment, in particular, as shown in FIG. 5, the convex portions 26 are formed by the outer edges 25A, 25B of both the groove walls 24B, 24C of the bottomed grooved slit 24.
Is formed so as to extend in the longitudinal direction.
That is, two convex portions 26 are provided on both sides of one bottomed grooved slit 24, and therefore, as shown in FIG. 5, a multi-core having two bottomed grooved slits 24 is provided. In the cable 10, a total of four convex portions 26 are provided.
Is formed. As described above, the protrusion 26 corresponds to FIGS.
As shown in FIG. 2, not only the outer edges 25A, 2B of the two groove walls 24B, 24C, but also
It may be formed along 5B.

Also, in the embodiment shown in FIGS. 4 and 5, the projection 26 has a substantially trapezoidal shape, so that the projection 26 shown in FIGS. Different from the example. As shown in FIG. 4, the projection 26 also has a function of preventing the interval between the two center conductors 18 from becoming unnecessarily small, as in the previous embodiment. Therefore, the shape of the convex portion 26 is not particularly limited as long as the interval between the center conductors 18 of the two insulated wires 12 can be prevented from becoming unnecessarily small.

In the illustrated embodiment, the multi-core cable 10 using the insulated wire 12 having the two grooved bottomed slits 24 has been described. However, the present invention is not limited to this. It is sufficient that one bottomed grooved slit 24 is formed. Generally, when the cross-sectional area of the center conductor 18 is relatively large, such as 2 mm ² or more, it is desirable to provide two or more grooved bottomed slits 24, and conversely, the cross-sectional area of the center conductor 18 is less than 2 mm ² In the case of, sufficient end workability can be ensured even with one bottomed grooved slit 24.

In the illustrated embodiment, when two bottomed grooved slits 24 are formed, the opening 27 of one of the bottomed grooved slits 24 is opposed to the opening 27 of the other bottomed grooved slit 24. The opening 27 is formed so as to face in the opposite direction by 180 °. However, the present invention is not limited to this, and the thickness T (see FIGS. 2 and 5) of the insulator 20 other than the protrusion 26 is reduced. When the insulator 20 is relatively thin and made of a flexible material, the opening 27 of one of the grooved bottomed slits 24 is 90 ° relative to the opening 27 of the grooved bottomed slit 24. In some cases, forming the terminal sideways improves the terminal workability. As described above, the number of the bottomed grooved slits 24 and their positional relationship are determined by the center conductor 18.
Of the insulator 20, the hardness of the insulator 20, the thickness of the insulator 20, and the like can be appropriately selected in consideration of workability.

In the illustrated embodiment, in order to prevent the insulator 20 from being torn in a normal state, the shape of the groove 24 having a bottom is substantially trapezoidal. The insulator 20 can be prevented from being torn from the grooved bottomed slit 24 when the insulator 20 is formed from the bottom, and if the grooved slit 24 is bottomed (that is, the center conductor 18 is exposed). If not, it may be another grooved bottomed slit 24 having, for example, a V-shape.

Next, some specific examples of the present invention will be described below. (Specific Example 1) Single-crystal copper wire 56 having a diameter of 0.18 mm
A concentric twisted book is used as a central conductor, and an insulator made of flexible vinyl chloride is coated on the central conductor, and the insulator extends longitudinally along the outer edge of one groove wall. Protrusions thus formed were provided to form insulated wires having the shapes shown in FIGS. In this case, the dimensions of each part are obtained by calculating the thickness T of the insulator (see FIG. 2) as T = 1.0 m.
m, the width W of the opening (see FIG. 2) is W = 0.5 mm,
The depth D of the bottomed grooved slit (see FIG. 2) is D = 0.6 m.
m, the thickness Tb (see FIG. 2) of the insulator at the bottom of the groove of the bottomed grooved slit was Tb = 0.4 mm, and the maximum thickness Tt of the projection (see FIG. 2) was Tt = 0.2 mm. . This 2
The two insulated wires are twisted in a left-handed twist, and as shown in FIG. 1, as a twisted body, a sheath made of vinyl chloride is coated on the twisted body to form a multi-core cable having an outer diameter of about 11 mm. did. As described above, by providing the protruding portion, even in a portion where the bottomed groove-like slits overlap each other, the interval between the two center conductors was not reduced, and stable electrical characteristics could be obtained. In addition, the thickness Tb (see FIG. 2) of the insulator at the bottom of the groove is as thin as 0.4 mm, so that the blade of the cutter can be appropriately moved along the groove with the bottom, and the force for pressing the blade of the cutter is small. In addition, the insulator could be peeled off cleanly without damaging the copper wires constituting the center conductor, and the end workability was improved.

(Specific Example 2) Twenty high-purity oxygen-free copper wires having a diameter of 0.18 mm are concentrically twisted to form a stranded wire.
These seven stranded wires were twisted in a rope shape to form a center conductor having a cross-sectional area of 5.25 mm ² . Next, an insulator made of polyethylene is coated on the center conductor, and the insulator is formed on the insulator so as to extend in the longitudinal direction along the outer edges of two groove walls for one grooved bottom. A portion was provided to form an insulated wire having the shape shown in FIG. In this case, the dimensions of each part are determined by the thickness T (see FIG. 5) of the insulator.
= 1.2 mm, and the width W of the opening (see FIG. 5) is W = 0.
6 mm and the depth D of the bottomed grooved slit (see FIG. 5)
= 0.7 mm, the thickness Tb of the insulator at the bottom of the groove of the bottomed grooved slit (see FIG. 5) is Tb = 0.5 mm, and the maximum thickness Tt of the projection is Tt = 0. It was 15 mm. As shown in FIG. 4, the two insulated wires were twisted to form a multi-core cable having an outer diameter of about 16 mm by coating a polyurethane sheath on the twisted body. In this way, the provision of the protruding portion allows the portion having the grooved bottomed slits to overlap with each other,
A stable electrical characteristic could be obtained without reducing the distance between the two center conductors. In addition, the thickness Tb of the insulator at the bottom of the groove (see FIG. 5) is 0.5 mm, which is smaller than the thickness T of the insulator at other portions (see FIG. 5). Can be moved properly, the force to press the blade of the cutter is small, and the insulator can be peeled off neatly without damaging the copper wire constituting the center conductor, and the end workability is improved. Could be improved.

[0032]

According to the present invention, as described above, a groove having a bottom is provided in an insulator, and a protrusion is formed so as to extend in a longitudinal direction along an outer edge of the groove having a bottom. Because of this, the thickness of the insulator is relatively thin at the groove bottom of the bottomed grooved slit, and the force for pressing the cutter blade is small, and the bottomed grooved slit makes it easier to insert the cutter blade. At the same time, since the bottomed grooved slit serves as a guide when the blade of the cutter moves, it is easy to appropriately move the blade of the cutter, so that the terminal can be easily processed without damaging the center conductor. There are benefits. At the same time, by improving the terminal workability in this way, the insulator can be formed from a relatively hard material capable of obtaining high-resolution sound quality, and these insulated wires are twisted and twisted. In the case of a body, since the material of the insulator is hard, the bottomed grooved slit does not easily deform, and even when the bottomed grooved slits of a plurality of insulated wires overlap, Since there is a margin depending on the thickness of the convex portion and it is possible to prevent the interval between the central conductors of the plurality of insulated wires from becoming unnecessarily small, there is a real benefit that the electrical characteristics can be stabilized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a multicore cable according to the present invention.

FIG. 2 is a sectional view of an insulated wire used in the multicore cable of the present invention.

FIG. 3 is a perspective view of the insulated wire shown in FIG. 2;

FIG. 4 is a sectional view of a multi-core cable according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of an insulated wire used in the multicore cable according to another embodiment shown in FIG.

FIG. 6 is a schematic view showing a state in which the insulator of the insulated wire is cut vertically by a cutter blade.

FIG. 7 is a cross-sectional view of a conventional multi-core cable.

8 is a cross-sectional view of a general insulated wire used for the conventional multi-core cable shown in FIG.

FIG. 9 is an end view of a prior art insulated wire used for a multi-core cable.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Multi-core cable 12 Insulated electric wire 14 Twisted body 16 Outer coating 18 Center conductor 20 Insulator 22 Sheath 24 Bottom grooved slit 24A Bottom grooved slit bottom 24B, 24C Bottom grooved slit wall 24D Yes Boundary line between groove bottom and groove wall of bottom grooved slit 25 Outer edge of groove wall of bottomed grooved slit 26 Projection 27 Opening 28 Cutter blade T Insulator thickness Tt Maximum thickness of protrusion Tb At groove bottom Insulator thickness W Opening width D Depth of bottomed grooved slit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01B 11/02 H01B 7/00 309 H01B 7/02 H01B 11/00

Claims (1)

(57) [Claims] 1. A twisted body formed by twisting a plurality of insulated wires each comprising a center conductor and an insulator provided in close contact with the center conductor, and A multi-core cable having at least one bottomed grooved slit extending in a longitudinal direction thereof, wherein the insulator comprises at least one groove of the bottomed grooved slit. A multi-core cable having a projection formed to extend in a longitudinal direction along an outer edge of a wall and protruding from an outer surface of the insulator.