Core wire for multi-core cable and multi-core cable
阅读说明：本技术 多芯电缆用芯电线以及多芯电缆 (Core wire for multi-core cable and multi-core cable ) 是由 松村友多佳 田中成幸 藤田太郎 小堀孝哉 石川雅之 于 2018-10-05 设计创作，主要内容包括：根据本公开的一个实施方案的多芯电缆用芯电线具有：通过将多根绞合线扭绞在一起而获得的导体；以及覆盖该导体的外周的绝缘层。绝缘层主要由聚乙烯树脂构成；绝缘层在25℃至-35℃的线性膨胀系数C1与绝缘层在-35℃的弹性模量E1的乘积,即(C1×E1)为0.01MPaK<Sup>-1</Sup>至0.90MPaK<Sup>-1</Sup>(包括端值)；并且聚乙烯树脂的熔点为80℃至130℃(包括端值)。(A core wire for a multi-core cable according to one embodiment of the present disclosure includes: a conductor obtained by twisting a plurality of strands together; and an insulating layer covering an outer periphery of the conductor. The insulating layer is mainly composed of polyethylene resin; the product of the linear expansion coefficient C1 of the insulating layer at 25-35 deg.C and the elastic modulus E1 of the insulating layer at-35 deg.C, i.e. (C1 × E1), is 0.01MPaK ‑1 To 0.90MPaK ‑1 (inclusive); and the polyethylene resin has a melting point of 80 ℃ to 130 ℃ (inclusive).)
1. A core wire for a multicore cable, comprising:
a conductor obtained by twisting a plurality of element wires; and
an insulating layer covering an outer circumferential surface of the conductor,
the insulating layer contains a polyethylene resin as a main component,
the insulating layer has a linear expansion coefficient C1 in the range of 25 to-35 ℃ multiplied by the elastic modulus E1 at-35 ℃, i.e., (C1 × E1) of 0.01MPaK-1Above 0.90MPaK-1Are as follows, and
the polyethylene resin has a melting point of 80 ℃ to 130 ℃.
2. The core wire for a multicore cable of claim 1, wherein
The insulating layer has an elastic modulus E2 of 100MPa or more at 25 ℃.
3. The core wire for a multicore cable according to claim 1 or 2, wherein
The insulating layer has a linear expansion coefficient C2 of 5.0 × 10 in the range of 25 deg.C to 80 deg.C-4K-1The following.
4. The core wire for a multicore cable according to any one of claims 1 to 3, wherein
The average area of the cross section of the conductor is 1.0mm2Above 3.0mm2The following.
5. The core wire for a multicore cable according to any one of claims 1 to 4, wherein
The average diameter of the plurality of element wires in the conductor is 40 to 100 [ mu ] m, and
the number of the plurality of element lines is more than 196 and less than 2450.
6. The core wire for a multicore cable according to any one of claims 1 to 5, wherein
The conductor is obtained by twisting a plurality of twisted wires, wherein each of the twisted wires is obtained by twisting a plurality of element wires.
7. A multi-core cable, comprising:
a cable core obtained by twisting a plurality of core wires; and
a jacket layer disposed about the cable core,
at least one of the plurality of core wires is the core wire according to claim 1.
8. The multi-core cable of claim 7, wherein
At least one of the plurality of core electric wires is a twisted core electric wire obtained by twisting a plurality of core electric wires.
Technical Field
The present disclosure relates to a core wire for a multicore cable and a multicore cable. This application claims the benefit of priority from japanese patent application No.2018-039137, filed on 3/5/2018, the entire contents of which are incorporated herein by reference.
Background
For a composite cable for a vehicle such as a cable for an Electric Parking Brake (EPB) or a cable for a wheel speed sensor, it may be bent complicatedly according to the installation condition in the vehicle or the driving of an actuator. Therefore, the bending resistance is important in terms of the performance of a composite cable for a vehicle such as a cable for an electric parking brake or a cable for a wheel speed sensor.
Further, the composite cable can be used in a low-temperature environment of 0 ℃ or lower. At such low temperatures, the insulating layer shrinks, thereby repeatedly pressing the conductor enclosed therein. Repeated squeezing can break the conductor and render it non-conductive. Conventionally, in order to improve the bending resistance in a temperature range from a low temperature to room temperature or higher, an insulating layer containing a copolymer of ethylene and an α -olefin having a carbonyl group as a main component has been proposed (see WO 2017/056278).
Reference list
Patent document
Patent document 1: WO 2017/056278
Disclosure of Invention
The core wire for a multi-core cable according to an embodiment of the present disclosure includes: conductor obtained by twisting a plurality of element wires(ii) a And an insulating layer covering the outer peripheral surface of the conductor. The insulating layer contains polyethylene resin as main component, and has a linear expansion coefficient of C1 in the range of 25 deg.C to-35 deg.C multiplied by the elastic modulus E1 at-35 deg.C, i.e. (C1 × E1) of 0.01MPaK-1Above 0.90MPaK-1The melting point of the polyethylene resin is 80 ℃ to 130 ℃.
Drawings
Fig. 1 is a sectional view schematically showing a core wire for a multi-core cable according to a first embodiment of the present disclosure;
fig. 2 is a cross-sectional view schematically illustrating a multi-core cable according to a second embodiment of the present disclosure;
fig. 3 is a view schematically showing a manufacturing apparatus of a multicore cable according to the present disclosure;
fig. 4 is a cross-sectional view schematically illustrating a multi-core cable according to a third embodiment of the present disclosure; and
fig. 5 is a view schematically showing a bending test performed in one example.
Detailed Description
[ problem to be solved by the present disclosure ]
The present inventors have found that even if the conductor is repeatedly bent at a temperature above room temperature at which the conductor is hardly broken, the insulating material may be worn or cracked, thereby rendering the conductor nonconductive. This wear or cracking of the insulation material is caused by the following interfacial friction: interfacial friction between core wires in the same jacket; interfacial friction between the jacket and the core wire; or, in the case of a paper winding structure, the interface friction between the winding paper and the core wire. Further, when fatigue fracture occurs in the insulating material due to repeated bending, the conductor may be exposed from the fracture, resulting in a problem in electrical conduction. Therefore, it is required to improve not only the bending resistance at low temperatures but also the bending resistance at room temperature and higher.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a core wire for a multi-core cable having excellent bending resistance not only at low temperatures but also at temperatures above room temperature, and a multi-core cable formed of the core wire.
[ advantageous effects of the present disclosure ]
The core wire for a multi-core cable according to the embodiment of the present disclosure has excellent bending resistance in a temperature range from a low temperature to room temperature or more.
[ description of embodiments of the present disclosure ]
A core wire for a multi-core cable according to an embodiment of the present disclosure includes a conductor obtained by twisting a plurality of element wires, and an insulating layer covering an outer peripheral surface of the conductor, the insulating layer containing a polyethylene-based resin as a main component, the insulating layer having a product of a coefficient of linear expansion C1 in a range of 25 ℃ to-35 ℃ and an elastic modulus E1 at-35 ℃, that is, (C1 × E1) of 0.01MPaK-1Above 0.90MPaK-1The melting point of the polyethylene resin is 80 ℃ to 130 ℃.
In the core wire for a multi-core cable, since the insulating layer contains a polyethylene-based resin as a main component and the product of the coefficient of linear expansion and the elastic modulus of the insulating layer at low temperature is limited to the above range, the core wire exhibits relatively high bending resistance at low temperature. The reason is probably because, since at least one of the coefficient of linear expansion or the elastic modulus is relatively small in the temperature range from low temperature to room temperature or more, the hardening (which may cause a decrease in flexibility) caused by the shrinkage of the insulating layer at low temperature is reduced, resulting in an increase in the bending resistance in the temperature range from low temperature to room temperature or more. Further, since the melting point of the polyethylene-based resin is 80 ℃ or more and 130 ℃ or less, the melting point of the insulating layer is higher than the temperature of the use environment, and thereby, the mechanical properties such as abrasion resistance and strength and the bending resistance of the insulating layer at room temperature or more can be improved. Therefore, the multi-core cable has excellent abrasion resistance and bending resistance in a temperature range from a low temperature to room temperature or more.
In the present disclosure, "linear expansion coefficient" is measured according to a test method of dynamic mechanical properties described in JIS-K7244-4(1999), and by using a viscoelasticity measuring apparatus (for example, "DVA-220" manufactured by IT Measurement & Control co., ltd.), a dimensional change of a sheet with respect to a temperature change is measured under conditions of a temperature range of-100 ℃ to 200 ℃, a temperature rise rate of 5 ℃/min, a frequency of 10Hz, and a strain of 0.05% in a tension mode, and the linear expansion coefficient is calculated from the dimensional change. "elastic modulus" was measured according to the test method for dynamic mechanical properties described in JIS-K7244-4(1999), and by using a viscoelasticity measuring apparatus (for example, "DVA-220" manufactured by IT Measurement & Control co., ltd.), the storage elastic modulus was measured in a tension mode under conditions of a temperature range of-100 ℃ to 200 ℃, a temperature rise rate of 5 ℃/min, a frequency of 10Hz, and a strain of 0.05%, and the elastic modulus was calculated from the storage elastic modulus. The "main component" means a substance having the highest content among substances constituting the insulating layer, and preferably a substance having a content of 50% by mass or more. The bending resistance means a property that the conductor does not break even if the wire or cable is repeatedly bent.
Preferably, the insulating layer has an elastic modulus E2 of 100MPa or more at 25 ℃. By setting the elastic modulus E2 of the insulating layer within the above range, the abrasion resistance and the bending resistance can be improved.
Preferably, the insulating layer has a linear expansion coefficient C2 of 5.0 × 10 in the range of 25 deg.C to 80 deg.C-4K-1The following. By setting the linear expansion coefficient C2 of the insulating layers within the above range, it is possible to reduce the contact pressure between the insulating layers in the sheath due to expansion of the insulating layers when the temperature becomes room temperature or higher, thereby reducing the interface friction between the insulating layers.
Preferably, the average area of the cross section of the conductor is 1.0mm2Above 3.0mm2The following. By setting the average area of the cross section of the conductor within the above range, the core wire can be applied to a multicore cable for a vehicle.
Preferably, the plurality of element wires in the conductor have an average diameter of 40 μm or more and 100 μm or less, and the number of the plurality of element wires is preferably 196 or more and 2450 or less. By setting the average diameter and the number of element wires within the respective ranges, the bending resistance of the core wire in the temperature range from low temperature to room temperature or higher can be further improved.
Preferably, the conductor is obtained by twisting a plurality of strands, wherein each strand is obtained by twisting a plurality of element wires. The bending resistance of the core electric wire can be improved by using a conductor obtained by twisting a plurality of twisted wires (i.e., a twice-twisted wire), each of which is obtained by twisting a plurality of element wires as described above.
A multi-core cable according to another embodiment of the present disclosure includes a cable core obtained by twisting a plurality of core electric wires and a sheath layer provided around the cable core, and at least one of the plurality of core electric wires is a core electric wire for a multi-core cable.
Since the multi-core cable includes the cable core composed of the core wire, the multi-core cable is excellent in bending resistance in a temperature range from a low temperature to room temperature or higher.
Preferably, at least one of the plurality of core electric wires is a twisted core electric wire obtained by twisting the plurality of core electric wires. By including stranded core wires in the cable core, a multi-core cable can be used in various applications while maintaining bending resistance.
[ details of embodiments of the present disclosure ]
Hereinafter, a core wire for a multicore cable and a multicore cable according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
[ first embodiment ]
The core wire 1 shown in fig. 1 is an insulated wire used for preparing a multi-core cable including a cable core and a sheath layer provided around the cable core. A cable core is obtained by twisting the core electric wire 1. The core wire 1 includes a conductor 2 in a linear shape and an insulating layer 3 as a protective layer covering the outer peripheral surface of the conductor 2.
The cross-sectional shape of the core wire 1 is not particularly limited, and may be, for example, a circular shape. When the cross-sectional shape of the core wire 1 is circular, the average outer diameter may be, for example, 1mm or more and 10mm or less depending on the use. The method for measuring the average outer diameter of the cross section of the core wire is not particularly limited. For example, the outer diameter of the core wire at arbitrary 3 positions is measured using calipers, and the average of the outer diameters measured at the 3 positions may be used as the average outer diameter.
< conductor >
The conductor 2 is obtained by twisting a plurality of element wires at a constant pitch. The plain wire is not particularly limited, and may be, for example, a copper wire, a copper alloy wire, an aluminum wire, or an aluminum alloy wire. Preferably, the conductor 2 is a double twisted strand obtained by twisting a plurality of strands, each strand being obtained by twisting a plurality of element wires. Preferably, each twisted wire is obtained by twisting an equal number of elementary wires.
The number of element wires may be appropriately selected according to the use of the multi-core cable, the diameter of the element wires, and the like, and the lower limit of the number of element wires is preferably 196, and more preferably 294. On the other hand, the upper limit of the number of element lines is preferably 2450, and more preferably 2000. As an example, the twice twisted strands may be: a double-twisted strand obtained by twisting 196 stranded wires, specifically, a double-twisted strand obtained by twisting 7 twisted strands, wherein each twisted strand is obtained by twisting 28 stranded wires; a double twisted strand obtained by twisting 294 elemental wires, specifically, a double twisted strand obtained by twisting 7 twisted strands, each twisted strand being obtained by twisting 42 elemental wires; a double twisted strand obtained by twisting 380 elemental wires, specifically, a double twisted strand obtained by twisting 19 twisted strands, wherein each twisted strand is obtained by twisting 20 elemental wires; a triple-twisted strand obtained by twisting 1568 element wires, specifically, a triple-twisted strand obtained by twisting 7 double-twisted strands (each double-twisted strand includes 224 element wires), each double-twisted strand being obtained by twisting 7 twisted strands, each twisted strand being obtained by twisting 32 element wires; or a triple-twisted strand obtained by twisting 2450 elemental wires, specifically, a triple-twisted strand obtained by twisting 7 double-twisted strands (each double-twisted strand includes 350 elemental wires), each double-twisted strand being obtained by twisting 7 twisted strands, each twisted strand being obtained by twisting 50 elemental wires.
The lower limit of the average diameter of the element wires is preferably 40 μm, more preferably 50 μm, and further preferably 60 μm. On the other hand, the upper limit of the average diameter of the element wires is preferably 100 μm, and more preferably 90 μm. If the average diameter of the element wires is less than the lower limit or greater than the upper limit, the bending resistance of the core electric wire 1 may not be sufficiently improved. The method for measuring the average diameter of the plain wire is not particularly limited. For example, the diameters at arbitrary 3 positions of the plain wire are measured using a micrometer having two cylindrical anvils, and the average of the diameters measured at the 3 positions may be used as the average diameter.
The lower limit of the average area of the cross section of the conductor 2 (including the gap between the element wires) is preferably 1.0mm2More preferably 1.5mm2More preferably 1.8mm2And even more preferably 2.0mm2. On the other hand, the upper limit of the average area of the cross section of the conductor 2 is preferably 3.0mm2And more preferably 2.8mm2. By setting the average area of the cross section of the conductor 2 within the above range, the core wire 1 can be applied to a multicore cable for a vehicle. The method of calculating the average area of the cross section of the conductor is not particularly limited. For example, the outer diameters of the conductors at arbitrary 3 positions are measured using calipers without crushing the twisted structure of the conductors, the average of the outer diameters measured at the 3 positions may be used as an average outer diameter, and the average area may be calculated from the average outer diameter.
< insulating layer >
The insulating layer 3 is formed from a composition containing a synthetic resin as a main component, and the insulating layer 3 covers the outer peripheral surface of the conductor 2 so as to cover the conductor 2. The average thickness of the insulating layer 3 is not particularly limited, and may be, for example, 0.1mm or more and 5mm or less. In the present disclosure, "average thickness" refers to the average of the thicknesses measured at 10 locations. In the following, the definition of the term "average thickness" applies equally to the other components.
The insulating layer 3 mainly contains a polyethylene resin. As an example, the polyethylene-based resin may be any polyethylene-based resin, such as high density polyethylene, low density polyethylene, linear low density polyethylene, or a copolymer of ethylene and an α -olefin. As examples of the polyethylene-based resin such as a copolymer of ethylene and α -olefin, an ethylene-vinyl acetate copolymer (EVA), an ethylene-ethyl acrylate copolymer (EEA), an ethylene-methyl acrylate copolymer (EMA), or an ethylene-butyl acrylate copolymer (EBA) can be cited. Among them, low density polyethylene or linear low density polyethylene is preferably used as the polyethylene resin. The polyethylene resin may be used alone or in combination of two or more. When two or more polyethylene resins are used in combination, the two or more polyethylene resins constitute the main component of the insulating layer 3. When two or more polyethylene-based resins are used, in order to balance characteristics such as elasticity at low and high temperatures, it is preferable to use a combination of HDPE and LDPE, a combination of HDPE and LLDPE, a combination of HDPE and EVA, and the like. In this case, the content of HDPE is preferably 10 mass% or more and 50 mass% or less with respect to the total content of the polyethylene resin. It is also preferred to use a combination of EVA and LDPE, a combination of EVA and LLDPE, and the like. In this case, the content of EVA is preferably 10 mass% or more and 50 mass% or less with respect to the total content of the polyethylene resin.
The lower limit of the melting point of the polyethylene-based resin is 80 ℃, preferably 85 ℃, and more preferably 90 ℃. On the other hand, the upper limit of the melting point is 130 ℃, preferably 120 ℃, and more preferably 110 ℃. If the melting point is below the lower limit, the melting point may be below the temperature of the use environment, and sufficient mechanical properties such as abrasion resistance and strength at room temperature or above may not be obtained. In contrast, if the melting point is higher than the upper limit, fatigue fracture and cracks may be generated, so that sufficient bending resistance may not be obtained. When a mixture of two or more polyethylene resins is used for the core wire for a multicore cable, the melting point of the mixture needs to be in the above range. For example, when two polyethylene-based resins are mixed, if the melting point of one polyethylene-based resin is within the above melting point range and the melting point of the other polyethylene-based resin is higher than 130 ℃, the mixture can be used as long as the melting point of the mixture is within the above range. In this case, if a polyethylene-based resin having a melting point within the above melting point range is used as the main component (50% by mass or more) of the polyethylene-based resin mixture, the melting point of the mixture can be adjusted to be within the above melting point range.
The lower limit of the content of the polyethylene-based resin is preferably 50 mass%, and more preferably 70 mass%. On the other hand, the upper limit of the content of the polyethylene-based resin is preferably 100 mass%, and more preferably 90 mass%. If the content of the polyethylene resin is less than the lower limit, the bending resistance may be insufficient in a temperature range from a low temperature to room temperature or higher.
The lower limit of the product C1 × E1 of the coefficient of linear expansion C1 of the insulating layer 3 in the range of 25 ℃ to-35 ℃ and the elastic modulus E1 at-35 ℃ is 0.01MPaK-1. On the other hand, the upper limit of the product C1 × E1 is 0.9MPaK-1Preferably 0.8MPaK-1More preferably 0.7MPaK-1. If the product C1 × E1 is less than the lower limit, mechanical properties such as strength of the insulating layer 3 may be insufficient. In contrast, if the product C1 × E1 is greater than the upper limit, the insulating layer 3 is not easily deformed at low temperatures, and as a result, the bending resistance of the core wire 1 at low temperatures may be insufficient. Note that the product C1 × E1 can be adjusted by adjusting the kind, content, and the like of the polyethylene-based resin.
The lower limit of the linear expansion coefficient C1 of the insulating layer 3 in the range of 25 ℃ to-35 ℃ is preferably 1.0X 10-5K-1And more preferably 1.0 × 10-4K-1. On the other hand, the upper limit of the linear expansion coefficient C1 of the insulating layer 3 is preferably 2.5 × 10- 4K-1And more preferably 2.0 × 10-4K-1. If the linear expansion coefficient C1 of the insulating layer 3 is less than the lower limit, mechanical properties such as strength of the insulating layer 3 may be insufficient. In contrast, if the linear expansion coefficient C1 of the insulating layer 3 is larger than the upper limit, the insulating layer 3 is less likely to be deformed at low temperatures, and as a result, the bending resistance of the core wire 1 at low temperatures may be insufficient.
The lower limit of the elastic modulus E1 at-35 ℃ of the insulating layer 3 is preferably 1000MPa, and more preferably 2000 MPa. On the other hand, the upper limit of the elastic modulus E1 of the insulating layer 3 is preferably 3500MPa, and more preferably 3000 MPa. If the elastic modulus E1 of the insulating layer 3 is less than the lower limit, mechanical properties such as strength of the insulating layer 3 may be insufficient. In contrast, if the elastic modulus E1 of the insulating layer 3 is greater than the upper limit, the insulating layer 3 is less likely to deform at low temperatures, and as a result, the bending resistance of the core wire 1 at low temperatures may be insufficient.
The lower limit of the linear expansion coefficient C2 of the insulating layer 3 in the range of 25 ℃ to 80 ℃ is preferably 1.0 × 10-4K-1And more preferably 2.0 × 10-4K-1. On the other hand, the upper limit of the linear expansion coefficient C2 of the insulating layer 3 is preferably 5.0 × 10-4K-1And more preferably 4.5 × 10-4K-1. If the linear expansion coefficient C2 of the insulating layer 3 is less than the lower limit, the compression of the conductor at room temperature or higher is not easily relieved, and as a result, the bending resistance of the conductor may be insufficient. In contrast, if the coefficient of linear expansion C2 of the insulating layer 3 is larger than the upper limit, the contact pressure between the insulating layers in the sheath may become large due to the expansion of the insulating layers at a temperature above room temperature, which may cause the insulating layers to wear and, as a result, the conductor is exposed, resulting in a problem in conduction.
The lower limit of the elastic modulus E2 of the insulating layer 3 at 25 ℃ is preferably 100MPa, and more preferably 200 MPa. On the other hand, the upper limit of the elastic modulus E2 of the insulating layer 3 is preferably 1000MPa, and more preferably 800 MPa. If the elastic modulus E2 of the insulating layer 3 is less than the lower limit, the abrasion resistance is poor, and the bending resistance may be insufficient. In contrast, if the elastic modulus E2 of the insulating layer 3 is greater than the upper limit, the bending rigidity of the cable increases, and as a result, the flexibility of the conductor may be insufficient.
The lower limit of the elastic modulus E3 of the insulating layer 3 at 80 ℃ is preferably 50MPa, and more preferably 100 MPa. On the other hand, the upper limit of the elastic modulus E3 of the insulating layer 3 is preferably 300MPa, and more preferably 200 MPa. If the elastic modulus E3 of the insulating layer 3 is less than the lower limit, the abrasion resistance is poor, and the bending resistance may be insufficient. In contrast, if the elastic modulus E3 of the insulating layer 3 is greater than the upper limit, the bending rigidity of the cable increases, and as a result, the flexibility of the conductor may be insufficient.
The insulating layer 3 may contain additives such as flame retardants, flame retardant aids, antioxidants, lubricants, colorants, reflection imparting agents, masking agents, processing stabilizers or plasticizers. The insulating layer 3 may contain other resins in addition to the polyethylene resin.
The upper limit of the content of the other resin is preferably 50% by mass, more preferably 30% by mass, and further preferably 10% by mass. Further, the insulating layer 3 need not contain other resin.
As an example, the flame retardant may be a halogen-based flame retardant such as a bromine-based flame retardant or a chlorine-based flame retardant, or a non-halogen-based flame retardant such as a metal hydroxide, a nitrogen-based flame retardant, or a phosphorus-based flame retardant. The flame retardant may be used alone or in combination of two or more.
Examples of the bromine-based flame retardant include decabromodiphenylethane and the like. Examples of the chlorine-based flame retardant include chlorinated paraffin, chlorinated polyethylene, chlorinated polyphenol, perchloropentadecane, and the like. As examples of the metal hydroxide, magnesium hydroxide or aluminum hydroxide may be cited. Examples of the nitrogen-based flame retardant include melamine cyanurate, triazine, isocyanurate, urea, guanidine, and the like. Examples of the phosphorus-based flame retardant include metal hypophosphite, phosphaphenanthrene, melamine phosphate, ammonium phosphate, phosphate ester, and polyphosphazene.
The lower limit of the content of the flame retardant in the insulating layer 3 is preferably 10 parts by mass, and more preferably 50 parts by mass, relative to 100 parts by mass of the resin component. On the other hand, the upper limit of the content of the flame retardant is preferably 200 parts by mass, and more preferably 130 parts by mass. If the content of the flame retardant is less than the lower limit, the flame retarding effect may be insufficient. In contrast, if the content of the flame retardant is greater than the upper limit, it is difficult to form the insulating layer 3 by extrusion molding, and mechanical properties such as elongation and tensile strength may be impaired.
Preferably, the resin component of the insulating layer 3 is crosslinked. As a method of crosslinking the resin component of the insulating layer 3, a method of irradiating the resin component with ionizing radiation, a method of using a thermal crosslinking agent such as an organic peroxide, or a method of adding a silane coupling agent to initiate the occurrence of a silane graft reaction can be cited.
< method for producing core wire for multicore cable >
The core wire 1 for a multicore cable can be manufactured by a method including: a step of twisting a plurality of element wires (twisting step); and a step of covering the outer peripheral surface of the conductor 2 obtained by twisting the plurality of element wires with an insulating layer 3 (insulating layer covering step).
As a method of covering the outer peripheral surface of the conductor 2 with the insulating layer 3, a method of extruding a composition for forming the insulating layer 3 onto the outer peripheral surface of the conductor 2 can be cited.
The method for manufacturing the core wire 1 for a multicore cable may further include a step of crosslinking the resin component of the insulating layer 3 (crosslinking step). The crosslinking step may be performed before the composition for forming the insulating layer 3 covers the conductor 2, or the crosslinking step may be performed after the covering (after the insulating layer 3 is formed).
Crosslinking can be performed by irradiating the composition with ionizing radiation. As the ionizing radiation, for example, gamma rays, electron beams, X rays, neutron beams, high-energy ion beams, and the like can be used. The lower limit of the irradiation dose of the ionizing radiation is preferably 10kGy, and more preferably 30 kGy. On the other hand, the upper limit of the irradiation dose of the ionizing radiation is preferably 300kGy, and more preferably 240 kGy. If the irradiation dose is less than the lower limit, the crosslinking reaction may not be sufficiently promoted. In contrast, if the irradiation dose is larger than the upper limit, the resin component may be decomposed.
[ advantages ]
The core wire 1 has improved bending resistance in a temperature range from a low temperature to room temperature or higher while maintaining insulation.
[ second embodiment ]
The multi-core cable 10 shown in fig. 2 includes a cable core 4 obtained by twisting a plurality of core electric wires 1 shown in fig. 1 and a jacket layer 5 provided around the cable core 4. The sheath layer 5 has an inner sheath layer (intermediate layer) 5a and an outer sheath layer (outer coating layer) 5 b. The multi-core cable 10 may be applicable as an electric cable for transmitting an electric signal to an engine driving a caliper of an electric parking brake.
The outer diameter of the multicore cable 10 can be appropriately adjusted according to various uses. The lower limit of the outer diameter is preferably 6mm, and more preferably 8 mm. On the other hand, the upper limit of the outer diameter of the multicore cable 10 is preferably 16mm, more preferably 14mm, further preferably 12mm, and particularly preferably 10 mm.
< Cable core >
The cable core 4 is obtained by twisting two core electric wires 1 having the same diameter in pairs. As described above, each core wire 1 includes the conductor 2 and the insulating layer 3.
< sheath layer >
The sheath layer 5 has a double-layer structure including an inner sheath layer 5a laminated on the outer surface of the cable core 4 and an outer sheath layer 5b laminated on the outer circumferential surface of the inner sheath layer 5 a.
The main component of the inner sheath layer 5a is not particularly limited as long as it is a synthetic resin having flexibility, and examples thereof include polyolefins such as polyethylene and EVA, polyurethane elastomers, polyester elastomers, and the like. Mixtures of two or more of these resins may be used.
The lower limit of the minimum thickness of the inner sheath layer 5a (the minimum distance between the cable core 4 and the outer peripheral surface of the inner sheath layer 5 a) is preferably 0.3mm, and more preferably 0.4 mm. On the other hand, the upper limit of the minimum thickness of the inner sheath layer 5a is preferably 0.9mm, and more preferably 0.8 mm. Further, the lower limit of the outer diameter of the inner sheath layer 5a is preferably 6.0mm, and more preferably 7.3 mm. On the other hand, the upper limit of the outer diameter of the inner sheath layer 5a is preferably 10mm, and more preferably 9.3 mm.
The main component of the outer jacket layer 5b is not particularly limited as long as it is a synthetic resin excellent in flame retardancy and wear resistance, and polyurethane may be cited as an example.
The average thickness of the outer jacket layer 5b is preferably 0.3mm to 0.7 mm.
The resin components in each of the inner sheath layer 5a and the outer sheath layer 5b are preferably crosslinked. The method of crosslinking the inner sheath layer 5a and the outer sheath layer 5b may be the same as the method of crosslinking the insulating layer 3.
The inner and outer jacket layers 5a, 5b may contain exemplary additives in the insulation layer 3.
Note that a tape member such as paper may be wound between the sheath layer 5 and the cable core 4 as an anti-wind member.
< method for producing multicore cable >
The multi-core cable 10 may be manufactured by a manufacturing method including: a step of twisting the plurality of core electric wires 1 (twisting step); and a step of covering a sheath layer on an outer surface of the cable core 4 obtained by twisting the plurality of core electric wires 1 (sheath layer covering step).
The method for manufacturing a multicore cable can be performed using the multicore cable manufacturing apparatus shown in fig. 3. The multi-core cable manufacturing apparatus is mainly equipped with a plurality of core
(twisting step)
In the twisting step, the core electric wires 1 wound on the plurality of core electric
(sheath layer covering step)
In the sheath layer covering step, the inner sheath
After covering the inner sheath layer 5a, the outer sheath
After covering the outer sheath layer 5b, the cable core 4 is cooled in the
The method for manufacturing a multicore cable may further include a step of crosslinking the resin component of the sheath layer 5 (crosslinking step). The crosslinking step may be performed before the resin composition for forming the sheath layer 5 is coated on the cable core 4, or the crosslinking step may be performed after the coating (after the formation of the sheath layer 5).
Crosslinking can be performed by irradiating the resin composition with ionizing radiation in the same manner as irradiating the insulating layer 3 of the core electric wire 1. The lower limit of the irradiation dose of the ionizing radiation is preferably 50kGy, and more preferably 100 kGy. On the other hand, the upper limit of the irradiation dose of the ionizing radiation is preferably 300kGy, and more preferably 240 kGy. If the irradiation dose is less than the lower limit, the crosslinking reaction may not be sufficiently promoted. In contrast, if the irradiation dose is larger than the upper limit, the resin component may be decomposed.
[ advantages ]
Since the multi-core cable 10 includes the cable core formed of the core wire 1, the multi-core cable 10 is excellent in bending resistance in a temperature range from a low temperature to room temperature or higher.
[ third embodiment ]
The multi-core cable 11 shown in fig. 4 includes a cable core 14 obtained by twisting a plurality of core electric wires shown in fig. 1 and a sheath layer 5 provided around the cable core 14. The multi-core cable 11 differs from the multi-core cable 10 shown in fig. 2 in that the cable core 14 is obtained by twisting a plurality of core wires having different diameters. The multicore cable 11 may be suitably used not only as a signal cable for an electric parking brake but also as a signal cable for transmitting an electric signal to control the operation of an anti-lock brake system (ABS). Since the sheath layer 5 is the same as the sheath layer 5 of the multicore cable 10 shown in fig. 2, the same reference numerals are given thereto, and a description thereof will not be repeated.
< Cable core >
The cable core 14 is obtained by twisting two first core electric wires 1a having the same diameter and two second core electric wires 1b having the same diameter, wherein the diameter of the second core electric wires 1b is smaller than that of the first core electric wires 1 a. Specifically, the cable core 14 is obtained by twisting two first core electric wires 1a and one twisted core electric wire obtained by twisting two second core electric wires 1 b. When the multi-core cable 11 is used as a signal cable for a parking brake and an ABS, the twisted core electric wires obtained by twisting the second core electric wires 2b transmit signals onto the ABS.
The first core wire 1a is the same as the core wire 1 shown in fig. 1. The second core wire 1b is the same in structure as the first core wire 1a except for a difference in sectional dimension, and the second core wire 1b is the same in material as the first core wire 1 a.
[ advantages ]
The multi-core cable 11 may be used not only to transmit an electric signal of an electric parking brake mounted on a vehicle but also to transmit an electric signal of an ABS.
[ other modifications ]
The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present disclosure is not limited to the configurations of the above-described embodiments, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.
The insulating layer of the core wire for a multi-core cable may have a multi-layer structure. Further, the sheath layer of the multicore cable may be a single layer, or may have a multilayer structure of three or more layers.
The multi-core cable may further include wires other than the wires of the present disclosure as core wires. However, in order to effectively exhibit the effects of the present disclosure, it is preferable that all the core wires in the multicore cable are the core wires of the present disclosure. The number of core wires in the multicore cable is not particularly limited as long as it is two or more, and the number of core wires may be six or more, for example.
The core wire for a multicore cable may have a primer layer directly covering the conductor. As the primer layer, a material obtained by crosslinking a crosslinkable resin such as ethylene containing no metal hydroxide can be suitably used. By providing such a primer layer, the insulating layer can be prevented from being detached from the conductor with the passage of time.