JPH08227619A - Multiple core cable - Google Patents

Abstract

PURPOSE: To improve terminal workability and to stabilize the electrical characteristic of a multiple core cable at the same time. CONSTITUTION: This multiple core cable 10 is formed of a twisted body 14 formed by alternately twisting two insulated wires 12 and an outer cover 16 provided on this twisted body 14. The insulated wire 12 is formed of a center conductor 18 and an insulating body 20 adhered onto this center conductor 18. This insulating body 20 has a groove-shaped slit 24 with bottom, which is extended along the longitudinal direction of the insulating body 20, and a projecting part 26, which is formed so as to be extended in the longitudinal direction along the outer edge of one groove wall 24C of the groove-shape slit 24 with bottom and which is projected from the outer surface of the insulating body 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a multi-core cable for signal transmission, which has a relatively large conductor diameter, such as a speaker cable used for electrically connecting an amplifier and a speaker of an audio device. The present invention relates to a multi-core cable capable of simultaneously improving terminal processability 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 electrically connecting an amplifier of an audio device and a speaker, generally has a structure as shown in FIG. A twisted body 14 formed by twisting a plurality of insulated electric wires 12 each including a center conductor 18 mainly made of copper and an insulator 20 provided in close contact with the center conductor 18, This twisted body 1
4 and an outer coating 16 provided on top of the base plate 4. The plurality of insulated wires 12 generally have a circular cross section, as shown in FIG.

A multi-core cable 1 having such a large conductor diameter
In the case of 0, for example, a speaker cable will be described as an example. In actual use, the insulator 20 of the insulated wire 12 is connected over about 20 to 30 mm in order to connect both ends thereof to a device such as an amplifier or a speaker. It is necessary to perform a terminal process of peeling off and exposing the central conductor 18. However, the insulator 20 is typically extrusion coated onto the center conductor 18,
In this case, since it is preferable to fix the center conductor 18 with the insulator 20 from the viewpoint of sound quality, pressure is applied to the insulator 20 to be extruded and coated to increase the degree of adhesion between the center conductor 18 and the insulator 20, and particularly, the center conductor. In the case where 18 is a stranded wire conductor in which fine wires are twisted together, it is common practice to increase the adhesion by allowing the insulator 20 to enter the valley of the twisting (for example, Japanese Patent Laid-Open No. 57-57). Japanese Patent Application No. 136119 (Japanese Patent Application No. 56-23932) "Cable for audio equipment" and the like).

Therefore, in such an insulated wire 12, since the central conductor 18 and the insulator 20 have a high adhesive force, the insulator 20 can be easily peeled off by a normally used hand stripper. After making a cut in the circumferential direction of the insulator 20 with a cutter that cannot be performed, as shown in FIG.
As shown in, it is necessary to insert a plurality of vertical slits with a cutter in the longitudinal direction of the insulator 20 and peel off the insulator 20 so that the banana is finally peeled.

[0005]

In this case, in the multicore cable 10 using the general insulated wire 12 shown in FIG. 8 having a circular cross section, the insulator 20 is made of FEP and PEP.
In the case of being formed from a relatively hard resin such as FA, a fluororesin, polypropylene, high density polyethylene, semi-rigid polyvinyl chloride, etc., the adhesion between the center conductor 18 and the insulator 20 is high and the insulator is high. Since 20 is hard, it is necessary to press the blade 28 of the cutter against the insulator 20 with a strong force. If this force is too strong, the center conductor 18 may be damaged or each of the twisted wires forming the center conductor 18 may be damaged. There is a risk of cutting the wires. Further, in order to make a vertical split in the longitudinal direction of the insulator 20, it is necessary to move the blade 28 of the cutter in the longitudinal direction of the insulator 20.
Since there is no guide for guiding the blade, it is difficult to move the blade 28 of the cutter linearly by bending the blade 28 of the cutter, and the center conductor 18 may be damaged. On the other hand, even when the insulator 20 is formed of a relatively flexible material such as vinyl chloride resin or rubber material, the insulator 20 adheres to the blade 28 of the cutter, so that the blade 28 of the cutter is always moved as desired. Can't let
Similarly, the center conductor 18 may be damaged. As described above, the general multicore cable 10 has a drawback that the workability at the time of terminal processing for stripping the insulator 20 to expose the center conductor 18 is low.

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

As described above, when the bottomed groove slit 24 is provided in the insulator 20, the end workability is improved, but the cross-sectional area of the central conductor 18 and thus the insulated wire 12 including the insulator 20 is large. When the insulator 20 is formed of a relatively flexible material such as vinyl chloride resin described above, when a plurality of insulated wires 12 are twisted to form a twisted body 14 as shown in FIG. The insulation 12 is deformed by compression or the like at the bottomed groove slits 24 due to the force applied to the insulated electric wires 12 during twisting, and as a result, in particular, the bottomed groove slits 24 of the plurality of insulated electric wires 12 are formed.
When they overlap each other, multiple insulated wires 1
The spacing between the two central conductors 18 may be reduced. As described above, in the portion where the distance between the center conductors 18 is small, the outer surface of the insulated wire 12 is dented and the characteristic impedance fluctuates. Therefore, the stability of the electrical characteristics in the longitudinal direction of the multi-core cable 10 decreases,
Problems such as signal reflection phenomenon and pulse fluctuation occur in pulse signals. Such a problem causes deterioration in sound quality particularly in an audio cable such as a speaker cable, and in a cable for transmitting an image signal,
There is a drawback that it appears as a decrease in resolution and lack of subtle expression.

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

[0009]

As a means for solving the above problems, the present invention provides a plurality of insulated electric wires each including a central conductor and an insulator closely attached to the central conductor. A multi-core cable including a twisted body formed by twisting the twisted wire and an outer coating provided on the twisted body, and the insulator having at least one bottomed groove-like slit extending in the longitudinal direction thereof. In, this insulator is
A multi-core cable characterized in that it has a convex portion formed so as to extend in the longitudinal direction along the outer edge of at least one groove wall of the bottomed groove-like slit and protruding from the outer surface of the insulator. is there.

[0010]

As described above, when the bottomed grooved slit is formed in the insulator and the convex portion 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 groove bottom, the thickness of the insulator is relatively thin, so the force of pressing the blade of the cutter is small, and
The bottomed groove-like slit makes it easier to insert the blade of the cutter, and the bottomed groove-like slit serves as a guide when the cutter blade moves, which facilitates proper movement of the cutter blade. The terminal can be easily processed without damaging the terminal. At the same time, by improving the terminal processability in this way, the insulator can be formed from a relatively hard material that can obtain sound quality with good resolution, and these insulated wires are twisted and twisted together. In the case of a body, since the material of the insulator is hard, the bottomed groove slit does not easily deform,
Further, even when the bottomed groove-shaped slits of a plurality of insulated electric wires are overlapped with each other, it is possible to prevent the distance between the central conductors of the plurality of insulated electric wires from being unnecessarily reduced due to the thickness of this convex portion. It is possible to realize stabilization of electric characteristics.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of the present invention will be described in detail. FIG. 1 shows a multi-core cable 10 of the present invention. A twisted body 14 formed by twisting the insulated wires 12 of each other, and an outer coating 1 provided on the twisted body 14.
It consists of 6 and.

As shown in FIGS. 1 and 2, each of the two insulated wires 14 comprises a center conductor 18 and an insulator 20 provided on the center conductor 18 in close contact therewith.
The center conductor 18 is formed of an appropriate conductor such as a single wire or a twisted wire made of a single crystal high-purity copper wire or a high-purity oxygen-free copper wire or the like. In order to prevent deterioration, the cross-sectional area is 0.
The outer diameter of the conductor is set to 75 mm or more, and the outer diameter of the conductor is set to about 1 mm or more.

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

The insulator 20 is provided in close contact with the central conductor 18 by extrusion coating on the central conductor 18. In this case, when 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 extruded and coated, 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 wire conductor in which thin wires are twisted together, it is preferable to increase the adhesion by allowing the insulator 20 to enter the valley of twisting. The insulator 20 is formed so as to cover the entire length of the central conductor 18, as shown in FIG.

The outer coating 16 is illustrated in FIG.
As shown in FIG.
To prevent the influence of external noise, this sheath 22
Alternatively, a shield (not shown) provided between the twisted body 14 and the sheath 22, or a suitable press winding may be applied to the shield.

In the multicore cable 10 of the present invention, the insulator 20 of the insulated wire 12 has a bottomed groove slit 24 extending in the longitudinal direction of the insulator 20, particularly as shown in FIG. In the illustrated embodiment, two bottomed groove-like slits 24 are provided at positions opposite to each other with an interval of 180 ° in the circumferential direction of the insulated wire 12. These bottomed grooved slits 24, as shown in FIG.
Two groove walls 24B located on the left and right of the groove bottom 24A,
24C has a substantially trapezoidal shape, and between the groove walls 24B and 24C, a blade 2 of a cutter described later is formed.
An opening 27 into which 8 is inserted is formed.

As described above, when the bottomed groove slit 24 is formed in the insulator 20, the workability of terminal processing for exposing the central conductor 18 shown in FIG. 6 to form a strip is improved.
That is, first, since the bottomed groove-shaped slit 24 forms the opening 27 in the insulator 20, the opening 27 facilitates insertion of the cutter blade 28 into the bottomed groove-shaped slit 24.
Further, in this case, the groove bottom portion 24 of the bottomed groove slit 24 is
Since the thickness Tb (see FIG. 2) of the insulator 20 at A is relatively thin, the force of pressing the blade 28 of the cutter is small. Further, the bottomed groove-shaped slit 24 serves as a guide for guiding the movement of the blade 28 of the cutter, and, for example, the blade tip of the blade 28 of the cutter is set to the groove bottom 24 of the bottomed groove-shaped slit 24.
A along the boundary line 24D between the groove walls 24B and 24C, or the surface of the blade 28 of the cutter is set to the groove walls 24B and 24C.
Since the blade 28 of the cutter can be moved while moving along C, the blade 28 of the cutter can be appropriately moved linearly.

Further, since the terminal processing can be easily performed in this manner, when the insulator 20 is vertically divided, the center conductor 18 is not damaged and the insulator 20 is made of chloride. Not only relatively soft materials such as vinyl resin and rubber materials, but also known to have low terminal processability due to their conventional hardness. Fluororesin 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 a sound quality with good resolution, and even when the twisted body 14 is formed, the insulator 20 is compressed and deformed at the bottomed groove slit 24, and the center of the insulator 20 is compressed. Since it is also advantageous in preventing the spacing between the conductors 18 from becoming unnecessarily small, it is very beneficial that the use of these materials does not have to be restricted in relation to the terminal processability. 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 groove slit 24 of the insulator 20. The protrusions 26 are formed and protrude 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 outer peripheral surface of the insulator 20 which is substantially concentric with the central 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 of the other portion
(T + T)
b: See FIG. 2).

Therefore, as shown in FIG. 1, the twisted body 1
4, the bottomed groove-shaped slits 2 of the plurality of insulated wires 12
Even in the portion where the four wires overlap each other, the convex portions 26 do not abut against each other's insulator 20 and the distance between the central conductors 18 of the two insulated wires 12 does not become smaller than necessary. In this case, in particular, even when a force is applied to the insulated wire 12 during the twisting and the insulator 20 is compressed, there is a margin corresponding to the thickness Tt of the convex portion 26 (see FIG. 2), so that there is a space between the two central conductors 18. It is possible to prevent the interval of (1) from becoming smaller than necessary. Therefore, the characteristic impedance does not fluctuate, a signal reflection phenomenon, pulse fluctuation, and the like do not occur, and it is possible to prevent the electrical characteristics in the longitudinal direction of the multi-core cable 10 from becoming unstable, and it is stable. The electrical characteristics can be maintained. Therefore, especially when the multi-core cable 10 is a speaker cable or a cable for transmitting an image signal, the sound quality is deteriorated and the resolution is reduced.
Further, it is possible to effectively prevent a subtle loss of expression.

As shown in FIG. 2, the convex portion 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 groove slit 24. As shown in FIG. 1, in the twisted body 14, there is a possibility that the gap between the center conductors 18 becomes small, particularly in the portion where the bottomed groove slits 24 of the plurality of insulated wires 12 overlap each other. This is because this is effectively prevented. However, if it is possible to prevent the distance between the center conductors 18 of the twisted body 14 from becoming small,
It is not always necessary to be continuous over the entire length of the bottomed groove slit 24, and for example, it may be provided intermittently in the longitudinal direction.

These bottomed groove slits 24 and convex portions 26
Is extruded using an extrusion die (not shown) having a shape corresponding to the bottomed groove slit 24 and the convex portion 26, or
Alternatively, the insulator 20 can be formed by forming the insulator 20 into a cylindrical shape slightly larger than a predetermined shape and then cutting the insulator 20. In this case, it is preferable that the convex portion 26 is formed integrally with the insulator 20 in this way, considering that the convex portion 26 is easily formed. 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 as needed, it is possible to ensure good end workability regardless of where it is cut. It is desirable that the bottom groove slit 24 and the convex portion 26 are continuously formed over the entire length of the insulated wire 12, as shown in FIG.

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 portion 26 has the outer edges 25A, 25B of both groove walls 24B, 24C of the bottomed groove 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 groove slit 24, and therefore, as shown in FIG. 5, two cored slits 24 are provided. The cable 10 has a total of four convex portions 26.
Is formed. In this way, the convex portion 26 has
As shown in FIG. 2, the outer edges 25A, 2A of both the two groove walls 24B, 24C are not limited to the one groove wall 24C side.
It may be formed along 5B.

In addition, in the embodiment shown in FIGS. 4 and 5, the convex portion 26 has a substantially trapezoidal shape. Therefore, the convex portion 26 is formed into a semi-cylindrical shape as shown in FIGS. 1 to 3. Different from the example. As shown in FIG. 4, this convex portion 26 also has a function of preventing the space between the two central conductors 18 from becoming smaller than necessary, as in the previous embodiment. Therefore, the shape of the convex portion 26 is not particularly limited as long as it is possible to prevent the gap between the central conductors 18 of the two insulated wires 12 from becoming smaller than necessary.

In each of the illustrated embodiments, the multi-core cable 10 using the insulated electric wire 12 having the two bottomed groove slits 24 has been described, but the present invention is not necessarily limited to this and at least It is sufficient that one bottomed groove slit 24 is formed. Generally, when the center conductor 18 has a relatively large cross-sectional area of 2 mm ² or more, it is desirable to provide two or more bottomed groove slits 24. Conversely, the center conductor 18 has a cross-sectional area of less than 2 mm ^2. In this case, even one bottomed groove slit 24 can ensure sufficient end workability.

Further, in the illustrated embodiment, when two bottomed grooved slits 24 are formed, one of the bottomed grooved slits 24 is provided with an opening 27 of the other bottomed grooved slit 24. The opening 27 is formed so as to face the opposite direction by 180 °, but the opening 27 is not necessarily limited to this, and the thickness T (see FIGS. 2 and 5) of the insulator 20 other than the protruding portion 26 is not limited to this. When the insulator 20 is made relatively thin and made of a flexible material, the opening 27 of one bottomed groove slit 24 is 90 ° with respect to the opening 27 of another bottomed groove slit 24. In some cases, the terminal workability may be improved by forming it so that it faces sideways. As described above, the number of the bottomed groove-shaped slits 24 and the mutual positional relationship are as follows.
Can be appropriately selected in consideration of the workability, depending on the outer diameter, the hardness of the insulator 20, the thickness of the insulator 20, and the like.

Further, in the illustrated embodiment, in order to prevent the insulator 20 from tearing in a normal state, the bottomed groove slits 24 are all trapezoidal in shape, but a relatively hard material is used. It is possible to prevent the insulator 20 from tearing from the bottomed groove-shaped slit 24 when the insulator 20 is formed from the bottom, and the groove-shaped slit 24 has a bottom (that is, the center conductor 18 is exposed). If not provided, other bottomed groove slits 24 having, for example, a V-shape may be used.

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 book in which the books are concentrically twisted together is used as a center conductor, and an insulator made of flexible vinyl chloride is coated on the center conductor, and the insulator extends in the longitudinal direction along the outer edge of one groove wall. By providing the convex portion thus formed, an insulated electric wire having a shape shown in FIGS. 2 and 3 was formed. In this case, the size of each part is the thickness T (see FIG. 2) of the insulator T = 1.0 m.
m and the width W of the opening (see FIG. 2) is W = 0.5 mm,
The depth D of the bottomed groove-like slit (see FIG. 2) is D = 0.6 m
m, the thickness Tb (see FIG. 2) of the insulator at the groove bottom of the bottomed groove-like slit is Tb = 0.4 mm, and the maximum thickness Tt of the protrusion (see FIG. 2) is Tt = 0.2 mm. . This 2
As shown in Fig. 1, two insulated electric wires are twisted in a left twist, and as a twisted body, a sheath made of vinyl chloride is coated on the twisted body to form a multi-core cable with an outer diameter of about 11 mm. did. As described above, by providing the convex portion, it is possible to obtain stable electrical characteristics without reducing the interval between the two central conductors even in the portion where the bottomed groove-shaped slits overlap each other. In addition, the thickness Tb (see FIG. 2) of the insulator at the groove bottom is as thin as 0.4 mm, so that the blade of the cutter can be appropriately moved along the bottomed groove slit, and the force of pressing the blade of the cutter is small. In addition, the insulator can be stripped off neatly without damaging the copper element wires constituting the center conductor, and the terminal processability can be improved.

(Specific Example 2) 30 high-purity oxygen-free copper wires having a diameter of 0.18 mm are concentrically twisted to form a stranded wire,
The seven twisted wires were twisted in a rope shape to form a center conductor having a cross-sectional area of 5.25 mm ² . Next, the center conductor is covered with an insulator made of polyethylene, and the insulator is formed with a protrusion formed so as to extend in the longitudinal direction along the outer edges of the two groove walls for one bottomed groove slit. A portion was provided to form an insulated electric wire having the shape shown in FIG. In this case, the size of each part is calculated by taking the thickness T of the insulator (see FIG. 5) as T
= 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 groove slit (see FIG. 5)
= 0.7 mm, the thickness Tb (see FIG. 5) of the insulator at the groove bottom of the bottomed groove-like slit is Tb = 0.5 mm, and the maximum thickness Tt of the convex portion (see FIG. 5) is Tt = 0. It was set to 15 mm. As shown in FIG. 4, the two insulated wires were twisted together to form a twisted body, and the twisted body was covered with a sheath made of polyurethane to obtain a multi-core cable having an outer diameter of about 16 mm. In this way, by providing the convex portion, even if the bottomed groove-shaped slits overlap each other,
It was possible to obtain stable electrical characteristics without reducing the distance between the two central conductors. Further, the thickness Tb (see FIG. 5) of the insulator at the bottom of the groove is 0.5 mm, which is thinner than the thickness T (see FIG. 5) of the insulator at other portions, and the blade of the cutter is guided along the bottomed groove slit. It can be moved appropriately, the force of pressing the blade of the cutter is small, and the insulator can be stripped off cleanly without damaging the copper strands that make up the center conductor, which improves the terminal processability. I was able to improve.

[0032]

According to the present invention, as described above, at the same time as providing the bottomed grooved slit in the insulator, the convex portion is formed so as to extend in the longitudinal direction along the outer edge of the bottomed grooved slit. Therefore, the thickness of the insulator is relatively thin at the groove bottom portion of this bottomed grooved slit, and the force to press the blade of the cutter is small, and the grooved bottomed slit makes it easier to insert the blade of the cutter. At the same time, since the bottomed groove-like slit serves as a guide when the blade of the cutter is moved, 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 is a real benefit. At the same time, by improving the terminal processability in this way, the insulator can be formed from a relatively hard material that can obtain sound quality with good resolution, and these insulated wires are twisted and twisted together. In the case of a body, since the material of the insulator is hard, the bottomed grooved slits do not easily deform, and even when the bottomed grooved slits of a plurality of insulated wires overlap each other, this There is a margin due to the thickness of the convex portion, and it is possible to prevent the intervals between the central conductors of the plurality of insulated electric wires from becoming smaller than necessary, so that there is a practical benefit that the electrical characteristics can be stabilized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a multi-core cable of the present invention.

FIG. 2 is a cross-sectional view of an insulated wire used in the multi-core cable of the present invention.

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

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

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

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

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 multi-core cable 12 insulated wire 14 twisted body 16 outer coating 18 center conductor 20 insulator 22 sheath 24 bottomed grooved slit 24A bottomed grooved groove bottom 24B, 24C bottomed grooved grooved wall 24D Boundary between the groove bottom and the groove wall of the bottom groove-shaped slit 25 Outer edge of the groove wall of the bottomed groove-shaped slit 26 Convex portion 27 Opening 28 Cutter blade T Insulator thickness Tt Maximum convex portion thickness Tb At the groove bottom Insulator thickness W Opening width D Bottom grooved slit depth

Claims (1)

[Claims] 1. A twisted body formed by twisting a plurality of insulated electric wires each comprising a center conductor and an insulator closely attached to the center conductor, and the twisted body on the twisted body. A multicore cable comprising an outer coating provided, wherein the insulator has at least one bottomed grooved slit extending in a longitudinal direction thereof, wherein the insulator is at least one groove of the bottomed grooved slit. A multi-core cable having a convex portion formed so as to extend in the longitudinal direction along the outer edge of the wall and protruding from the outer surface of the insulator.