JPH05120926A - Small-diameter cable with excellent mechanical strength - Google Patents

Abstract

PURPOSE:To provide a small-diameter cable with excellent electric characteristics, acoustic characteristics, and machinability, as well as with tensile strength equivalent to or higher than that of a piano wire conductor, without using the piano wire conductor. CONSTITUTION:Spiral coatings 4, 6, 8 are applied over the outer periphery of a conductor assembly 1, 2 composed of a conductor and an insulation-coated conductor being less deofrmable by a compression force orthogonally acting toward a center axis, or prepared through assembling a plurality of these conductors. They 4, 6, 8 are prepared through spiral winding therearound of a wire or a strip member having a higher tensile strength and a smaller elongation than those of the conductors. The tension applied on such a cable as constituted in this way in the axial direction thereof is converted into a tension of the spiral coating and a compression force acting toward a center axis of the conductor assembly. Since the tension applied on the cable in the axial direction thereof is converted into the tension of the spiral coatings and the compression force acting toward the center axis of the conductor assembly, it is possible to achieve a high tensile strength without using a piano wire conductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin cable having high mechanical strength.

[0002]

2. Description of the Related Art Recent electronic devices are digitized, LSI
With the progress of miniaturization, miniaturization has been remarkable, and along with this, the demand for thinner cables has also continued to increase. For example, even one microphone with an outer diameter of about 4 mm has appeared, and its cable is also a shield wire with 2 to 3 cores, an outer diameter of about 1 mm to 2 mm and a tensile strength of 20 kgf to 40 kgf are becoming necessary. ..

The biggest problem with a small-diameter cable is that its tensile strength is particularly low among its mechanical strength. As long as it is based on the same material and the same structure, the tensile strength is proportional to the square of the outer diameter of the cable. Therefore, if the outer diameter decreases, the tensile strength sharply decreases. On the other hand, fatigue due to bending, which is another point of mechanical properties, increases in inverse proportion to the square of the wire diameter as long as the same conductive material is used. It just becomes a problem. This is because if the conductor wire is made thinner to make the cable thinner, the strength against fatigue is inevitably increased. As described above, in the case of a small diameter cable, that is, a cable of less than about 3 mmφ, insufficient tensile strength is the biggest problem, and it is necessary to obtain a tensile strength exceeding 15 to 20 kgf which is a practical strength.
Extremely difficult.

Pulling a small diameter cable with a large force,
When a tensile impact is applied, the first thing that happens is a conductor break, which is a fatal defect for the cable and makes it unusable. This is because the elongation of the conductor is the smallest among the various materials that compose the cable, and even a copper conductor with relatively good ductility can obtain a breaking elongation of about 10 to 20%, and a copper alloy or a copper wire can obtain a breaking elongation of about 1 to 5%. .. On the other hand, the elongation of the insulator is usually 100 to 300%, which is extremely larger than that of the conductor material. In addition, the Young's modulus of an insulating material is usually smaller than that of a conductor material as a metal, and easily expands even with a small force. Therefore, most of the mechanical strength is determined by the tensile strength of the conductor material.

Conventionally, the only technique to cope with such an application is to use a conductor material having a large tensile strength. For example, "Senheiser", a world-class microphone manufacturer in West Germany, uses metal as a metal. We have developed a small-diameter cable that uses "piano wire", which has the highest tensile strength, as a conductor element wire, and has realized a two-core comprehensive shielded cable with an outer diameter of 2.2 mm and a tensile strength of 40 kgf. An example of this is shown in Fig. 5, in which 11 is a 7 / 0.12mm piano wire, 12 is a 0.55mm polyester insulator, 13 is a 0.36mm polyester monofilament, and 14 is about 35 / 0.10mm copper horizontal. The winding shield, 15 is a 2.2 mm PVC jacket, and its tensile strength is about 40 kgf. The tensile strength of the piano wire is 300kgf / mm ²
Therefore, it can be seen that the tensile strength of the finished cable is almost determined by the tensile strength of the conductor as long as it is based on the existing design technology.

This method is currently the only method that can realize such a tensile strength, and is mechanically close to an ideal and sufficiently satisfactory, but has the following problems. That is, 1) The electrical resistance is an order of magnitude higher than that of a copper conductor, and if the cable is made longer, the attenuation is increased and it cannot be used. That is,
Maximum usable cable length is reduced by an order of magnitude. 2) For audio, there is a serious defect, which has become common sense, that the sound quality is deteriorated due to non-linearity and eddy current, and it cannot be used by a user with excellent pitch. 3) Solderability is poor, and the blade is worn out significantly during cutting. Have big problems such as. Nevertheless,
Currently, this is considered to be the highest, "copper foil thread" in which copper foil or copper wire is wound around a core thread of polyester, etc., which has excellent mechanical strength, as in conventional thin cables, or "horizontal winding". This is because a method using a material having a good balance of electrical characteristics and mechanical characteristics, such as a "conductor" or a copper alloy wire, cannot achieve half the strength.

[0007] For example, the microphone cord of Japan "Sony" company for the same purpose is designed by such an existing method, so that it has the same outer diameter and the same as that of "Senheiser" company using the piano wire. Despite being a two-core comprehensive shield, it only shows a tensile strength of about 18 kgf, which is less than 1/2 of the code of "Senheiser". That is, an example thereof is shown in FIG. 6, in which 21 is an aramid fiber reinforcing material, 22 is a 16 / 0.06 mm copper horizontal conductor, 23 is a polyethylene insulator, and 24 is a polyester thread interposer (filler). ), 25 is 16/4 / 0.08mm copper braided shield, 26 is 2.2mm
It is a PVC jacket and its tensile strength is about 18 kgf.

[0008]

SUMMARY OF THE INVENTION The present invention seeks to address the above drawbacks based on a new design principle.
The purpose is to: a) use an existing conductor material with excellent electrical, acoustic and workability, such as copper or copper alloy, without using steel wire such as piano wire, b) , It is to realize the strength equal to or higher than that of a piano wire conductor by a completely different principle. That is, the small-diameter cable according to the present invention is “reverse” to the method using the piano wire conductor, and does not try to maximize the tensile strength of the conductor, but is “wider” than the conductor cross section, It aims to achieve the object by increasing the tensile strength of the structural portion.

[0009]

The gist of the small diameter cable according to the present invention is that a conductor, an insulating coated conductor or a plurality of these which are not deformed by a compressive force acting at a right angle toward the central axis. On the outer periphery of the assembled conductor assembly, a wire or band material having a larger Young's modulus and less elongation is spirally wound, and a spiral coating is applied to apply tension applied in the axial direction of the cable to the spiral coating material. And a compressive force toward the central axis of the conductor assembly.

The construction principle of the present invention lies in the following two points A and B. A) The outer circumference of the "conductor assembly" is "greater in tensile strength" than that of the conductor or the conductor assembly so as to enclose the conductor of the cable, the insulation-coated conductor, or a conductor assembly formed by bundling a plurality of these conductors, and Cover with a "helix-coated" structure with "less" material. The reason why the spiral structure is necessary is to be able to bend the whole cable,
When the coating of the spiral structure is pulled in the axial direction of the cable,
This is because the inner diameter is reduced and a compressive force is applied to the conductor assembly. For example, a cylindrical coating that does not stretch will not bend and will not generate compressive force. Also, if the tensile strength of the material forming this spiral coating is small, the spiral coating will break before the conductor, and if it easily extends, the tension of the cable will be directly applied to the conductor and the same result as the conventional product will be obtained. Will end up.

Specifically, as the material of the "low elongation", "high tensile strength", and "spiral coating", a thread typified by aramid fiber, copper alloy wire or copper wire having high tensile strength is used. However, these may be used as a horizontal winding structure, a braiding structure, a spiral extrusion structure, or the like. The cross section of the copper wire or the steel wire may be a plate-shaped one other than the circular shape. A braid or horizontal winding structure using both copper wire and fiber or copper wire and steel wire may be used. This means that the shield layer also serves as a "helical coating with a low elongation", and also prevents an increase in the outer diameter due to the addition of the "helical coating".
It is the method of three birds with one stone. In addition to braiding and horizontal winding,
There are various realization methods such as spiral extrusion.

The above is the essential part of the present invention. Due to this "helical coating" structure, the tension of the entire cable is not the conductor itself, but the "tension of the material forming the helical coating".
And is converted to "compressive force on the conductor assembly". As a result, what is needed is the following conditions for the conductor assembly.

B) A conductor or an insulation-coated conductor, or a "conductor assembly" formed by bundling and twisting or assembling them, is designed to have a "compression-resistant" hard structure. That is, when a large force is applied inward from the outer periphery of the conductor assembly, that is, toward the central axis, at a right angle to the central axis,
Use a structure that does not easily change the outer diameter. This means that the Young's modulus of the assembly as a whole is large without shrinking even when tightened from the outside. Specifically, a hard insulator having a large Young's modulus may be used, and the structure may be such that there is no gap between the conductor and the insulating coated conductor. As will be described later, this condition can be realized relatively easily by the stress distribution mechanism unique to the present invention. Obtain sufficient practical compressive strength by assembling conductors coated with common insulating materials such as fluororesin, polyester resin, polyethylene, vinyl chloride compound, etc. without leaving gaps between them. You can

[0014]

The operation and effect based on the two constitutional principles described in A and B above will be discussed in more detail here. First, from the structure described in A, the tension of the entire cable is applied to "high tensile strength", "low elongation of material", and "spiral coating", and the axial tension reduces the outer diameter of the helical coating. Will act in the direction.

That is, since the tension F of the entire cable balances with the reaction force against contraction, which is perpendicular to the axial direction of the cable, the "conductor assembly" covered with the spiral sheath must not easily contract. .. However, it should be noted that the shrinkage stress itself is a value obtained by dividing the cable tension F by the “surface area of the spiral coating”, and therefore can be made significantly smaller than the stress applied to the “conductor cross section”. is there. That is, since the surface area of the "helical coating">> the cross-sectional area of the conductor, the contraction stress of the conductor assembly << the stress in the axial direction of the cable is established, and the contraction force of the "conductor assembly" becomes extremely small. That is, "conductor assembly"
It is hard to shrink to the extent necessary for the present invention and does not shrink, which is compatible with practical flexibility, and the flexibility against bending and the strength against compression are not contradictory properties. This is the first point of the present invention.

Another point is that the tensile strength of the material forming the "helical coating" is larger than that of other parts such as the conductor, and it is necessary to withstand the tension of the entire cable without breaking the conductor. In this case, In this case, the advantageous condition peculiar to this structure also acts. That is, the cross-sectional area of the "helical sheath" arranged on the outer periphery of the cable >>
The cross-sectional area of the conductor in the center of the cable holds. Therefore, strengthening the spiral coating is relatively easy as compared to strengthening the conductor. For example, taking the two-core total shield illustrated above as an example, even if the "helical coating" has a single horizontal winding structure with a wire having the same outer diameter as the conductor, the conductor cross-sectional area = 0.1 mm ² (7 /0.1mm × 2) The cross-sectional area of the shield is 0.2mm ² (25 / 0.1mm). It can be seen that even if the same material is used, about twice the tensile strength can be obtained. If there are two layers, it is four times. Furthermore, copper and copper alloy are used for the conductor, and "helical coating"
If aramid fiber, piano wire, etc. are used for the material, the difference in strength exceeding one digit can be obtained because the material alone has a gap of several times to one digit.

Thus, the condition required by the conventional design method, that is, the tensile strength of a conductor having a small cross-sectional area ≅
The difficult condition of tension is: i) The tensile strength of the "helical coating" with a large cross section ≒ Cave
Compressive force big the tensile strength ii) surface area needed to Le "spiral coating"> Cave
It can be seen that it can be converted into a very advantageous condition that the tensile strength required for the tool (here, ≈ means that the left and right sides are almost equal, and> means that the left side is large). In essence, the difference in cross-sectional area and surface area of the "conductor" located in the center of the cable and the "helical coating" located near the outer circumference of the cable is the source of this difference.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As an actual design example based on the above principle, some embodiments of the present invention are shown in FIGS. FIG. 1 shows a first embodiment of a two-core comprehensive shielded cable having an outer diameter of 1.6 mm according to the present invention, in which 1 is 19/0.
03mm copper or copper alloy conductor, 2 0.35mm polyester insulator, 3 filler (this is to maintain the circular cross section of the cable and to improve the appearance, not necessarily an essential component. The same applies in the example as well.) 4 is a spiral braided sheath that also serves as a shield by a mixed braid in which 8 carriers of 6 / 0.04 mm copper wire and 8 carriers of 200 denier aramid fiber are alternately woven, and 5 is a normal PVC.
It is a 1.6 mm jacket made of (vinyl chloride) compound, and this structure could achieve a tensile strength of 31 kgf. By increasing the number of aramid fibers, 40kgf
The above is practically sufficient, and the structure of the piano wire conductor is 2
It has been found that about twice the tensile strength can be obtained without sacrificing electrical characteristics, acoustic characteristics, workability, and the like.

FIG. 2 shows a second embodiment of a two-core comprehensive shielded cable having an outer diameter of 1.6 mm according to the present invention, in which 1 is a conductor of 19 / 0.03 mm copper or copper alloy, 2 Is a 0.35 mm polyester insulation, 3 is a filler, 5 is a 1.6 mm jacket made of a normal PVC compound (the above is the same as the case of the embodiment of FIG. 1), 6 is a spiral coating made of braided aramid fiber, and 7 is approximately 45 / 0.06 copper horizontal winding shield,
With this structure, a tensile strength of 55 kgf could be obtained.

FIG. 3 shows a third embodiment of a two-core comprehensive shielded cable having an outer diameter of 1.6 mm according to the present invention, in which 1 is a conductor of 19 / 0.03 mm copper or copper alloy, 2 Is a 0.35 mm polyester insulator, 3 is a filler, 5 is a 1.6 mm jacket made of a normal PVC compound (the above is the same as the case of the embodiment of FIG. 1), 7 is about 47 / 0.06 copper horizontal winding shield, and 8 is It is a spiral coating of horizontal winding of aramid fiber,
With this structure, a tensile strength of 49 kgf could be obtained.

FIG. 4 shows the first embodiment of the present invention shown in FIG. 1 and the second embodiment shown in FIG. 2, and the cable outer diameter (mm) and tensile strength (kgf) of a conventional small-diameter cable. 5 is a graph showing the relationship between the two, where x is the value of a typical cable currently in circulation, ◯ is the value of the high tensile strength cable based on the existing technology shown in FIGS. 5 and 6, and ◎ is the present invention. These are the values of the above-mentioned first, second and third embodiments.

[0022]

Since the present invention is constructed as described above, the existing conductor material such as copper or copper alloy having excellent electric characteristics, acoustic characteristics and workability is used without using a piano wire conductor unlike the existing method. Can be used to provide a thin cable having a tensile strength equal to or higher than that of a piano wire conductor. It should be noted that the present invention is not limited to the above embodiments, and includes all modified embodiments that can be easily conceived by those skilled in the art from the above description within the scope of the object.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a thin cable according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the thin cable according to the present invention.

FIG. 3 is a cross-sectional view showing still another embodiment of the thin cable according to the present invention.

FIG. 4 is a graph showing the relationship between the cable outer diameter and the tensile strength of a thin cable according to the present invention and an existing thin cable.

FIG. 5 is a cross-sectional view showing an example of a thin cable according to the existing method.

FIG. 6 is a cross-sectional view showing another example of a thin cable according to the existing method.

[Explanation of symbols]

 1 Copper conductor 2 Polyester insulator 3 Filler 4 Copper-aramid fiber mixed braid 5 PVC jacket 6 Aramid fiber braid 7 Copper horizontal winding shield 8 Aramid fiber horizontal winding 11 Piano wire 12 Polyester insulation 13 Polyester monofilament 14 Copper horizontal winding shield 15 PVC Jacket 21 Aramid fiber reinforcement 22 Horizontal copper conductor 23 Polyethylene insulator 24 Polyester thread interposer 25 Copper braided shield 26 PVC jacket

Claims (5)

[Claims] 1. A conductor material which is less likely to be deformed by a compressive force acting at a right angle toward a central axis, an insulating coating conductor, or a conductor assembly (1, 2) formed by assembling a plurality of these conductors, on the outer periphery of the conductor material. A spiral coating (4,6,8) made by spirally winding a wire or strip with higher tensile strength and less elongation is applied to reduce the tension applied in the axial direction of the cable to the tension of the spiral coating and the center of the conductor assembly. A small-diameter cable with excellent mechanical strength, which is configured to be converted into a compressive force directed to the shaft. 2. The small-diameter cable with excellent mechanical strength according to claim 1, wherein the spiral coating is a spiral transverse winding (8). 3. The small diameter cable having excellent mechanical strength according to claim 1, wherein the spiral coating is a spiral braid (6). 4. The small diameter cable excellent in mechanical strength according to claim 1, wherein the spiral coating is made of aramid fiber. 5. A small-diameter cable having excellent mechanical strength according to claim 1, wherein the spiral coating is composed of a mixed braid (4) of aramid fiber and copper wire or a mixed transverse winding.