Cable

Abstract

To provide a cable exhibiting low dust generation, reduced flammability, and a small outer diameter.SOLUTION: A cable 1 comprises an assembled core 4 composed of a plurality of electric wires 2, and a covering layer 7 that covers the periphery of the assembled core 4 and constitutes an outermost layer, wherein the covering layer 7 is composed of a dust generation suppressing layer that passes CLASS1 in a cleanliness class in accordance with ISO14644-1, and a combustion suppressing layer 6 having an oxygen index that is 5 or more higher than an oxygen index of the covering layer 7 is provided between the covering layer 7 and the assembled core 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cable. [Background technology]

[0002] Conventionally, cables to be wired to devices such as industrial robots include, for example, cables that include an aggregate core formed by twisting together multiple electric wires (insulated electric wires, twisted pair wires formed by twisting pairs of insulated electric wires, etc.) and a sheath that covers the aggregate core (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-218061 Summary of the Invention [Problem to be solved by the invention]

[0004] Cables used in industrial robots and machine tools, or cables used in clean environments such as semiconductor manufacturing equipment, require low dust generation and flame retardancy in addition to excellent abrasion resistance and flex resistance. In particular, the sheath provided on the outermost part of the cable is required to suppress the generation of dust caused by contact with other components and rubbing against the surface (i.e., a low-dust generation sheath).

[0005] On the other hand, there is a trend toward increasing the number of wires in cables to improve the functionality of devices such as industrial robots, but this also increases the proportion of combustible materials in the cable, making it more flammable. Therefore, it is also desirable to make the sheath more flame-resistant.

[0006] However, if the amount of flame retardant added to the sheath is increased to make it less flammable, the sheath will be more likely to generate dust when it rubs against other components, etc. In order to make the sheath less flammable without increasing the amount of flame retardant added, it is possible to increase the thickness of the sheath, for example, but in this case, the outer diameter of the cable will increase, making it difficult to wire.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide a cable that generates little dust, is flame-resistant, and has a small outer diameter. [Means for solving the problem]

[0008] The present invention aims to solve the above-mentioned problems and provides a cable comprising an aggregate core made up of a plurality of electric wires, and a covering layer that surrounds the aggregate core and forms the outermost layer, wherein the covering layer is made of a dust-suppressing layer that meets Class 1 cleanliness standards in accordance with ISO 14644-1, and wherein a combustion-suppressing layer is provided between the covering layer and the aggregate core and has an oxygen index that is 5 or more higher than the oxygen index of the covering layer. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a cable that generates little dust, is flame-resistant, and has a small outer diameter. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a cable according to an embodiment of the present invention. [Figure 2] 10(a) and 10(b) are cross-sectional views showing a cross section perpendicular to the longitudinal direction of a cable according to another embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a cable according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Embodiment Mode] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0012] (Overall configuration of cable 1) 1 is a cross-sectional view perpendicular to the longitudinal direction of a cable 1 according to this embodiment. Cable 1 is used in, for example, industrial robots, machine tools, or semiconductor manufacturing equipment, and is used in clean environments where dust generation is undesirable.

[0013] As shown in Fig. 1, the cable 1 includes an aggregate core 4 made up of a plurality of electric wires 2, and a covering layer 7 (sheath) that surrounds the aggregate core 4 and constitutes the outermost layer. In this embodiment, a holding winding tape 5 is provided around the aggregate core 4, a combustion suppressing layer 6 is provided so as to surround the holding winding tape 5, and a covering layer 7 is provided so as to surround the combustion suppressing layer 6. Each layer will be described in detail below.

[0014] (Electric wire 2) The electric wire 2 is an insulated electric wire 2a composed of a conductor 21 and an insulator 22 covering the conductor 21. However, the electric wire 2 is not limited to this, and may be a coaxial wire in which a shield layer and a jacket layer are further provided in that order around the insulator 22, or a twisted pair wire in which a pair of insulated electric wires 2a are twisted together. The conductor 21 is formed by twisting together a plurality of metal wires made of copper or a copper alloy. The metal wires may be plated with tin, silver, or the like. In this embodiment, the conductor 21 is formed using a tin-plated annealed copper wire having an outer diameter of 0.1 mm or less. The outer diameter of the conductor 21 is, for example, 1.0 mm or less.

[0015] The insulator 22 is provided to cover the conductor 21 and is formed by, for example, tube extrusion. The thickness of the insulator 22 is, for example, 0.1 mm or more and 0.4 mm or less. The outer diameter of the insulator 22, i.e., the outer diameter of the electric wire 2, is, for example, 0.7 mm or more and 3.0 mm or less.

[0016] The insulator 22 can be made of a fluororesin such as ETFE (ethylene-tetrafluoroethylene copolymer), or a non-fluororesin. In recent years, the use of fluororesins has been reduced to reduce environmental impact, and from the perspective of reducing environmental impact, it is more preferable to use a non-fluororesin. Furthermore, it is more preferable that the specific gravity of the insulator 22 is 1.0 or less. This makes the electric wire 2 lighter, and the weight of the cable 1 can be reduced, thereby further reducing dust generation due to friction between the cable 1 and surrounding components. As a non-fluororesin having a specific gravity of 1.0 or less, PP (polypropylene) or irradiation-crosslinked PP can be suitably used.

[0017] (Collective Core 4) In this embodiment, the collective core 4 is formed by twisting together six insulated wires 2a and a fiber filler 3. The six insulated wires 2a are arranged in a line in the circumferential direction of the cable, and adjacent insulated wires 2a in the circumferential direction are prevented from coming into direct contact with each other by the fiber filler 3. The fiber filler 3 may be a fibrous filler made of staple fiber yarn, nylon, or the like. The fiber filler 3 is arranged in the center of the cable 1. The fiber filler 3 may be filled between adjacent wires 2 in the circumferential direction or between the wires 2 and the holding winding tape 5.

[0018] Here, the collective core 4 is formed by twisting together multiple (six) insulated electric wires 2a, but this is not limiting. For example, the collective core 4 may be formed by twisting together multiple twisted pairs, each of which is formed by twisting together a pair of insulated electric wires 2a. The collective core 4 may also be formed by twisting together multiple child twisted wires, each of which is formed by twisting together two or more insulated electric wires 2a. Furthermore, the collective core 4 may include a linear body or tube made of resin. For example, the collective core 4 may be formed by twisting together multiple electric wires 2 around a linear body located in the center of the cable.

[0019] (Pressing tape 5) The holding winding tape 5 is wound spirally around the collective core 4. Examples of the holding winding tape 5 that can be used include resin tapes made of non-foamed resins such as PE (polyethylene), PP, and PVC (polyvinyl chloride), foamed resin tapes made of foamed resins such as foamed PP, nonwoven fabrics, and Japanese paper.

[0020] (Combustion-suppressing layer 6 and coating layer 7) In the cable 1 according to the present embodiment, a combustion-suppressing layer 6 is provided to cover the periphery of the holding winding tape 5, and a covering layer 7 is provided to cover the periphery of the combustion-suppressing layer 6. In the cable 1, the covering layer 7, which serves as the outermost layer, and the combustion-suppressing layer 6 are provided so as to be in direct contact with each other. For example, if a large amount of flame retardant is added to the covering layer 7 to improve the flame retardancy of the covering layer 7, the flame retardant is a powdery filler, which makes it prone to dust generation. As in the present embodiment, by providing a combustion-suppressing layer 6 that is separate from the covering layer 7 and is an inner layer relative to the covering layer 7, and that contains more flame retardant than the covering layer 7 and has higher flame retardancy than the covering layer 7, it is possible to improve the flame retardancy of the entire cable 1 while reducing the amount of flame retardant added to the covering layer 7 and thereby suppressing dust generation.

[0021] The combustion suppression layer 6 is provided between the covering layer 7 and the aggregate core 4. The combustion suppression layer 6 is formed by extrusion coating using insertion extrusion or tube extrusion with a resin composition that is more flame-retardant than the covering layer 7, or by wrapping a flame-retardant tape member. Here, the combustion suppression layer 6 is formed from a resin composition that uses polyvinyl chloride resin as the base resin and contains a larger amount of flame retardant than the covering layer 7. Examples of the flame retardant that can be used include flame retardants containing antimony trioxide, aluminum hydroxide, magnesium hydroxide, phosphorus, etc.

[0022] The coating layer 7 functions as a dust-suppressing layer that meets Class 1 cleanliness standards in accordance with ISO 14644-1 and is made of a resin composition based on polyvinyl chloride resin. To suppress dust generation, the amount of flame retardant added to the coating layer 7 is adjusted to be significantly less than that of the combustion-suppressing layer 6. As with the combustion-suppressing layer 6, the flame retardant may be, for example, a flame retardant containing antimony trioxide, aluminum hydroxide, magnesium hydroxide, phosphorus, or the like.

[0023] As described above, it is desirable to reduce the amount of flame retardant added to the coating layer 7 to suppress dust generation, thereby lowering the oxygen index (the minimum oxygen concentration required for a material to sustain combustion). On the other hand, it is desirable to have a high oxygen concentration in the combustion-suppressing layer 6 to improve the flame retardancy of the cable 1. In the cable according to this embodiment, the combustion-suppressing layer 6 has an oxygen index that is at least 5 higher than that of the coating layer 7. More preferably, the difference between the oxygen index of the coating layer 7 and that of the combustion-suppressing layer 6 is between 7 and 15. More specifically, it is desirable that the oxygen index of the combustion-suppressing layer 6 be 30 or higher and the oxygen index of the coating layer 7 be 25 or lower. This results in a cable 1 that is both flame-retardant and low-dust-generation. The oxygen index can be measured using an oxygen index tester according to a test method conforming to JIS K 7201-2.

[0024] Furthermore, the mass of the coating layer 7 per unit length of cable (hereinafter referred to as the basis weight (kg / km) of the coating layer 7) should be greater than the mass of the combustion-suppressing layer 6 per unit length of cable (hereinafter referred to as the basis weight of the combustion-suppressing layer 6). More specifically, the basis weight of the coating layer 7 should be 1.5 to 6.5 times the basis weight of the combustion-suppressing layer 6. This is because if the basis weight of the coating layer 7 is less than 1.5 times the basis weight of the combustion-suppressing layer 6, the coating layer 7 will be too thin, resulting in insufficient dust-generation suppression and a reduction in the mechanical strength of the coating layer 7, making it more susceptible to breakage. Furthermore, if the basis weight of the coating layer 7 is more than 6.5 times the basis weight of the combustion-suppressing layer 6, the combustion-suppressing layer 6 will be too thin, resulting in reduced flame retardancy. For the same reason, the thickness of the combustion-suppressing layer 6 should be 20 to 65% of the thickness of the coating layer 7. In this embodiment, the thickness of the combustion suppression layer 6 is set to 0.2 mm or more and 0.5 mm or less, and the thickness of the coating layer 7 is set to 0.8 mm or more and 1.0 mm or less.

[0025] Although not shown, the cable 1 may include a shielding layer made of a braided shield or the like. The shielding layer may be provided between the covering layer 7 and the combustion suppressing layer 6, or between the combustion suppressing layer 6 and the holding winding tape 5.

[0026] (Dust generation test) A dust generation test was conducted on Cable 1. In the dust generation test, Cable 1 was housed in a Cableveyor (registered trademark), and a U-shaped bending motion was applied to the Cableveyor (registered trademark) (one end was fixed in a U-shaped state, and the other end was repeatedly slid along the cable's length), and the particles generated during this motion were measured with a particle counter. The moving speed v and acceleration / deceleration a during the U-shaped bending motion were determined under the following three conditions: Condition 1: v=0.5m / s, a=1.0m / s 2 Condition 2: v=1.0m / s, a=2.0m / s 2 Condition 3: v=2.0m / s, a=5.0m / s 2 The dust generation test was carried out for three types of cables 1 with different outer diameters. The test results are summarized in Table 1.

[0027] [Table 1]

[0028] Dust generation tests were conducted on three types of cables with different outer diameters, masses, and densities (weight converted into unit volume), as shown in Table 1. As the density (weight converted into unit volume), operating speed v, and acceleration / deceleration rate a increase, the conditions for dust generation become more severe, but it was confirmed that under all conditions the cables passed Class 1 in the cleanliness class compliant with ISO14644-1. The passing condition for Class 1 in the cleanliness class compliant with ISO14644-1 is that particles with a particle size of 0.1 μm travel at a speed of 1 m. 3 The condition is that there must be no more than 10 items.

[0029] (Flame retardancy test) The cable 1 was also subjected to a VW-1 test and a Cable Flame test in accordance with UL1581. The outer diameter of the cable 1 was approximately 6.0 mm, and a fluororesin (ETFE) was used as the insulator 22 of the electric wire 2. The flame retardancy test was also conducted on Example 1, in which a shielding layer was provided between the coating layer 7 and the combustion-suppressing layer 6, and Example 2, in which a shielding layer was provided between the combustion-suppressing layer 6 and the holding tape 5. The shielding layer in Examples 1 and 2 was a cross-woven braided shield using tin-plated annealed copper wire and fiber wire (spunbond yarn). For comparison, a comparative cable in which the combustion-suppressing layer 6 was omitted was also subjected to a flame retardancy test in the same manner as Examples 1 and 2. As a result of the flame retardancy test, both Examples 1 and 2 passed both the VW-1 test and the Cable Flame test. The inventors' investigations revealed that when the combustion-suppressing layer 6 starts to burn after the coating layer 7 burns, non-combustible gas is generated from the combustion-suppressing layer 6, and it is believed that this non-combustible gas and the endothermic reaction that occurs when the non-combustible gas is generated inhibit the spread of fire in the coating layer 7. On the other hand, the comparative example in which the combustion-suppressing layer 6 was omitted failed both the VW-1 test and the Cable Flame test.

[0030] (Actions and Effects of the Embodiments) As described above, in the cable 1 according to the present embodiment, the coating layer 7 is made of a dust-suppressing layer that meets Class 1 cleanliness standards in accordance with ISO 14644-1, and a combustion-suppressing layer 6 having an oxygen index 5 or more higher than that of the coating layer 7 is provided between the coating layer 7 and the collective core 4. This results in a cable 1 that has improved flame retardancy while suppressing dust generation. Furthermore, the provision of the combustion-suppressing layer 6 eliminates the need to thicken the coating layer 7, making it possible to prevent the cable 1 from becoming larger in diameter.

[0031] (Other embodiments) The cable 1a shown in Figure 2(a) has basically the same configuration as the cable 1 in Figure 1, but differs in that it has three twisted pairs 23 twisted together to form an aggregate core 4, and that it has a shielding layer 8 between the combustion suppression layer 6 and the aggregate core 4 (between the combustion suppression layer 6 and the holding winding tape 5).

[0032] It is desirable that the twist direction of the twisted pairs 23 and the twist direction of the assembly core 4 are the same. This reduces the load on the wires 2 when they are bent or otherwise subjected to bending, thereby improving resistance to bending or other such motions. The twist direction of the twisted pairs 23 is the direction in which the wires 2 rotate from one end to the other when viewed from one end of the twisted pairs 23. The twist direction of the assembly core 4 is the direction in which the twisted pairs 23 rotate from one end to the other when viewed from one end of the cable 1.

[0033] In cable 1a, shield layer 8 is made of a braided shield. To reduce the weight of cable 1, shield layer 8 may be made of a cross-woven braided shield made by braiding multiple metal wires (e.g., tin-plated annealed copper wire) and multiple fiber wires (e.g., staple fiber yarn), or a braided shield made by braiding metal foil yarns (e.g., copper foil yarns) in which metal foil is wrapped around fiber yarns. This makes cable 1 lighter and can further reduce dust generation due to friction with surrounding components.

[0034] In cable 1a, a shielding layer 8 is provided between the combustion suppressive layer 6 and the assembly core 4, and the combustion suppressive layer 6 is in contact with the coating layer 7. Therefore, when cable 1a burns (i.e., when the outermost coating layer 7 burns), combustion gas is more likely to be generated from the combustion suppressive layer 6, which is an underlying layer of the coating layer 7, thereby further enhancing the flame retardant effect. In addition, by forming the combustion suppressive layer 6 as far outward as possible in the cable radial direction (i.e., at a position closer to the coating layer 7), the basis weight can be increased even for a combustion suppressive layer 6 of the same thickness, and the combustion suppressive effect of the coating layer 7 is further enhanced.

[0035] The cable 1b shown in FIG. 2(b) is the same as the cable 1a shown in FIG. 2(a), except that a shielding layer 8 is provided between the coating layer 7 and the combustion-suppressing layer 6. As with the cable 1a shown in FIG. 2(a), the shielding layer 8 may be formed of an interwoven braided shield or a braided shield made of braided metal foil threads. If the combustion-suppressing layer 6 is formed of a tape member, the holding tape 5 can be omitted. By providing the combustion-suppressing layer 6 as an inner layer of the shielding layer 8, the combustion-suppressing layer 6 also serves as an abrasion-suppressing layer that suppresses friction between the shielding layer 8 and the collective core 4, thereby suppressing combustion of the coating layer 7 and improving resistance to movements such as bending.

[0036] The cable 1c shown in FIG. 3 is the cable 1a shown in FIG. 2(a) with a shielding layer 8 formed by wrapping a conductive tape 81, which is a conductive tape member. When the conductive tape 81 is used as the shielding layer 8, a reinforcing pressure winding tape 5 may be provided on the outer layer of the shielding layer 8 in addition to the inner layer of the shielding layer 8. Furthermore, a drain wire 82 for grounding the conductive tape 81 may be provided in contact with the inner circumferential surface of the conductive tape 81. The drain wire 82 is a stranded wire formed by twisting together multiple metal wires, such as annealed copper wires. The stranded wire is preferably a bunched stranded wire. Using a bunched stranded wire makes it easier for the drain wire 82 to sink toward the bundled core 4, as shown in FIG. 3, and therefore the outer shape of the shielding layer 8 formed by wrapping the conductive tape 81 around it tends to be uniform around the cable circumference. As a result, even if the cable 1c includes the drain wire 82, the drain wire 82 is less likely to break when the cable 1c is repeatedly bent, and damage to the conductive tape 81 by the drain wire 82 can be prevented.

[0037] The conductive tape 81 has a substrate and a conductive layer made of conductive resin provided on the surface of the substrate. The substrate is made of a resin such as a polyolefin-based resin as the base resin and is formed in a long strip shape. The conductive layer is made of a conductive resin whose base resin is a resin such as a polyolefin-based resin with conductive fine particles dispersed in the base resin. The conductive tape 81 is wound spirally so that portions of the conductive tape 81 overlap in the width direction. By forming the shielding layer 8 from the conductive tape 81, the shielding layer 8 can be formed in the same process as twisting the collective core 4 and winding the pressure winding tape 5. This reduces the number of manufacturing steps and enables lower manufacturing costs compared to when the shielding layer 8 is formed from a braided shield.

[0038] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiments will be described by using the reference numerals and the like in the embodiments. However, the reference numerals and the like in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiments.

[0039] [1] A cable (1) comprising: an aggregate core (4) consisting of a plurality of electric wires (2); and a covering layer (7) surrounding the aggregate core (4) and constituting the outermost layer, wherein the covering layer (7) is made of a dust-suppressing layer that meets CLASS 1 cleanliness standards in accordance with ISO 14644-1; and a combustion-suppressing layer (6) between the covering layer (7) and the aggregate core (4) that has an oxygen index that is 5 or more higher than the oxygen index of the covering layer (7).

[0040] [2] The cable (1) according to [1], wherein the difference between the oxygen index of the coating layer (7) and the oxygen index of the combustion-suppressing layer (6) is 7 or more and 15 or less.

[0041] [3] The cable (1) according to [1], wherein the oxygen index of the combustion-suppressing layer (6) is 30 or more, and the oxygen index of the covering layer (7) is 25 or less.

[0042] [4] The cable (1) according to [1], wherein the mass of the covering layer (7) per unit length of the cable is greater than the mass of the combustion suppression layer (6) per unit length of the cable.

[0043] [5] The cable (1) according to [1], wherein the thickness of the combustion-suppressing layer (6) is 20% or more and 65% or less of the thickness of the covering layer (7).

[0044] [6] The cable (1a, 1c) according to [1], further comprising a shielding layer (8) between the combustion suppression layer (6) and the collective core (4).

[0045] [7] The cable (1b) according to [1], further comprising a shielding layer (8) between the covering layer (7) and the combustion suppression layer (6).

[0046] [8] The cable (1a, 1b) according to [6] or [7], wherein the shielding layer (8) is made of an interwoven braided shield in which a plurality of metal wires and a plurality of fiber wires are braided.

[0047] [9] The cable (1a, 1b) according to [6] or [7], wherein the shielding layer (8) is made of a braided shield made of metal foil threads in which metal foil is wrapped around fiber threads.

[0048]

[10] The cable (1c) according to [6], wherein the shielding layer (8) is formed by wrapping a conductive tape (81) that is a conductive tape member.

[0049]

[11] The cable (1) described in [1], wherein the plurality of electric wires (2) are insulated electric wires (2a) consisting of a conductor (21) and an insulator (22) surrounding the conductor (21), and the specific gravity of the insulator (22) is 1.0 or less.

[0050] (Addendum) Although the embodiments of the present invention have been described above, the invention according to the claims is not limited to the above-described embodiments. It should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention. Furthermore, the present invention can be appropriately modified and implemented within the scope of its spirit. [Explanation of symbols]

[0051] 1...Cable 2...Electric wire 2a...Insulated wire 3...Fiber interposition 4...Collective Core 5...Pressing tape 6...Combustion retardant layer 7…Covering layer 8...Shield layer 21...conductor 22...Insulator 81...Conductive tape 82...Drain wire

Claims

1. a core assembly made up of a plurality of electric wires; a coating layer that covers the periphery of the aggregate core and constitutes an outermost layer, the coating layer is a dust-generation-suppressing layer that meets Class 1 cleanliness standards in accordance with ISO 14644-1; a combustion-suppressing layer having an oxygen index 5 or more higher than the oxygen index of the coating layer between the coating layer and the aggregate core; cable.

2. the difference between the oxygen index of the coating layer and the oxygen index of the combustion-suppressing layer is 7 or more and 15 or less; The cable of claim 1 .

3. The oxygen index of the combustion-suppressing layer is 30 or more, The coating layer has an oxygen index of 25 or less. The cable of claim 1 .

4. the mass of the coating layer per unit length of the cable is greater than the mass of the combustion suppression layer per unit length of the cable; The cable of claim 1 .

5. The thickness of the combustion suppression layer is 20% or more and 65% or less of the thickness of the coating layer. The cable of claim 1 .

6. A shield layer is provided between the combustion suppression layer and the collective core. The cable of claim 1 .

7. A shield layer is provided between the coating layer and the combustion suppression layer. The cable of claim 1 .

8. The shield layer is made of an interwoven braided shield in which a plurality of metal wires and a plurality of fiber wires are braided.

8. A cable according to claim 6 or 7.

9. The shield layer is made of a braided shield formed by braiding metal foil yarns in which metal foil is wrapped around fiber yarns.

8. A cable according to claim 6 or 7.

10. The shielding layer is formed by wrapping a conductive tape, which is a conductive tape member.

7. The cable of claim 6.

11. The plurality of electric wires are insulated electric wires each including a conductor and an insulator covering the conductor, The specific gravity of the insulator is 1.0 or less. The cable of claim 1 .

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