Patent Application
20240212878
The present disclosure relates to a multicore cable.
This application claims priority to Japanese Patent Application No. 2021-077349 filed Apr. 30, 2021, which is incorporated herein by reference in its entirety.
PTL 1 discloses a core electric wire used in automotive multicore cables for electronic parking brakes (EPBs), wheel speed sensors, or other systems. The core electric wire has a conductor and two insulating layers covering the conductor and made of resins. One of the insulating layers contains a copolymer of ethylene and an α-olefin having a carbonyl group, and the other insulating layer contains a polyolefin or a fluororesin.
A multicore cable according to an aspect of the present disclosure includes: a core wire made by stranding a pair of first core electric wires and a wire; and a sheath layer disposed around the core wire, wherein the first core electric wires each include a conductor and an insulating layer covering an outer surface of the conductor, and a ratio d2/d1 of an average outer diameter d2 of the wire to an average outer diameter d1 of each first core electric wire is more than 0.5 and less than 2.0.
Automotive multicore cables for electronic parking brakes, wheel speed sensors, or other systems are complicatedly flexed during handling in vehicles, driving of actuators, or other operations. Such an automotive multicore cable thus requires high flex resistance. There is also a need to easily remove a sheath layer at terminals of multicore cables (hereinafter also referred to as “good terminal processability”) to improve workability.
The present disclosure has been made in light of the foregoing circumstances and aims at providing a multicore cable having high flex resistance and good terminal processability.
A multicore cable according to an aspect of the present disclosure has high flex resistance and good terminal processability.
First, embodiments of the present disclosure are listed and described.
A multicore cable according to an aspect of the present disclosure includes: a core wire made by stranding a pair of first core electric wires and a wire; and a sheath layer disposed around the core wire, wherein the first core electric wires each include a conductor and an insulating layer covering an outer surface of the conductor, and a ratio d2/d1 of an average outer diameter d2 of the wire to an average outer diameter d1 of each first core electric wire is more than 0.5 and less than 2.0.
The multicore cable has high flex resistance and good terminal processability when the ratio d2/d1 of the average outer diameter d2 of the wire to the average outer diameter d1 of each first core electric wire is more than 0.5 and less than 2.0. The “flex resistance” refers to the ability of an electric wire or cable to withstand repeated flex with no break in conductor. The multicore cable also has high flex resistance at low temperature. The “low temperature” refers to a temperature range of 0° ° C. or lower.
The wire is preferably a second core electric wire including a conductor and an insulating layer covering the outer surface of the conductor. In this case, the multicore cable has a symmetric cross section, and the multicore cable has higher flex resistance.
Preferably, the wire is a stranded core electric wire including a core wire made by stranding multiple third core electric wires and a sheath layer disposed around the core wire, and the third core electric wires each include a conductor and an insulating layer covering the outer surface of the conductor. In this, the multicore cable has still higher flex resistance.
The ratio D/d1 of the average outer diameter D of the multicore cable to the average outer diameter d1 of each first core electric wire is preferably more than 2.7 and less than 4.0. This configuration can promote the effect of improving the flex resistance and terminal processability of the multicore cable.
The multicore cable is suitably used as an automotive cable.
A multicore cable according to an embodiment of the present disclosure will be described below with reference to the drawings.
A multicore cable 1 shown in
The multicore cable 1 may have any cross-sectional shape and has, for example, a circular cross section. The average outer diameter D of the multicore cable 1 can be appropriately designed according to the application. The lower limit of the average outer diameter D is, for example, 6 mm, preferably 8 mm, and the upper limit of the average outer diameter D is, for example, 16 mm, preferably 12 mm. The “average outer diameter” refers to the average value of the outer diameter of the cross section at freely selected ten points. For example, if the cross section is flat, and the measured diameter varies depending on how the diameter is taken, the average value of the maximum outer diameter and the minimum outer diameter is regarded as the outer diameter.
In the multicore cable 1, the ratio d2/d1 of the average outer diameter d2 of the wire 3 to the average outer diameter d1 of each core electric wire 2 is more than 0.5 and less than 2.0. With the ratio d2/d1 in the above range, the multicore cable 1 has high flex resistance and good terminal processability. The reason for this is not necessarily clear, but may be that, with the ratio d2/d1 in the above range, the core wire 4 has a uniform cross-sectional shape, and the bunch stranded structure of the core wire 4 is hardly distorted when the multicore cable 1 is flexed, resulting in high flex resistance. When the core wire 4 has a uniform cross-sectional shape, the sheath layer 5 has a constant thickness in the circumferential direction, and the depth of blade insertion is constant in removing the sheath layer 5, resulting in good terminal processability.
The lower limit of the ratio d2/d1 is preferably 0.7, more preferably 0.8, still more preferably 1.0. The upper limit of the ratio d2/d1 is preferably 1.7, more preferably 1.5, still more preferably 1.3. With the ratio d2/d1 in the above range, the multicore cable 1 has higher flex resistance and better terminal processability. In addition, the space inside the sheath layer 5 can be reduced to improve the stability of the cross-sectional shape.
In the multicore cable 1, the ratio D/d1 of the average outer diameter D of the multicore cable 1 to the average outer diameter d1 of each core electric wire 2 is preferably more than 2.7 and less than 4.0. With the ratio D/d1 in the above range, the multicore cable 1 has higher flex resistance and better terminal processability. The lower limit of the ratio D/d1 is more preferably 2.8, still more preferably 3.0. With the ratio D/d1 greater than or equal to the lower limit, the multicore cable 1 has higher flex resistance. The upper limit of the ratio D/d1 is more preferably 3.7, still more preferably 3.5. With the ratio D/d1 less than or equal to the upper limit, the multicore cable 1 has higher terminal processability.
The core wire 4 is a bunch stranded wire made by stranding a pair of core electric wires 2 and a wire 3.
The core electric wires 2 each include a conductor 2b and an insulating layer 2a covering the outer surface of the conductor 2b. The pair of core electric wires 2 has the same average outer diameter. The “same” in this case means that a difference in average outer diameter between the pair of core electric wires 2 is 5% or less of the outer diameter of the smaller core electric wire 2.
The lower limit of the average outer diameter d1 of each core electric wire 2 is, for example, 1.3 mm, preferably 2.0 mm, and the upper limit is, for example, 5.0 mm, preferably 4.5 mm.
The conductor 2b is a conductor made by stranding multiple element wires at a constant pitch. Examples of the element wires include, but are not limited to, copper wires, copper alloy wires, aluminum wires, and aluminum alloy wires. The conductor 2b is preferably a stranded stranded wire made by stranding multiple stranded element wires each made by stranding multiple element wires. The stranded element wires to be stranded preferably have the same number of element wires.
The lower limit of the average diameter of each element wire is preferably 40 μm, more preferably 50 μm, still more preferably 60 μm. The upper limit of the average diameter of each element wire is preferably 100 μm, more preferably 90 μm. The average diameter of each element wire refers to the average diameter of the element wire at freely selected three points as measured by using a micrometer with both columnar ends.
The number of element wires is appropriately designed according to, for example, the application of the multicore cable 1 or the diameter of the element wires. The lower limit of the number of element wires is preferably 196, more preferably 294. The upper limit of the number of element wires is preferably 2450, more preferably 2000. Examples of the stranded stranded wire include a stranded stranded wire having 196 element wires and made by stranding 7 stranded element wires each made by stranding 28 element wires, a stranded stranded wire having 294 element wires and made by stranding 7 stranded element wires each made by stranding 42 element wires, a stranded stranded wire having 380 element wires and made by stranding 19 stranded element wires each made by stranding 20 element wires, a stranded stranded stranded wire having 1568 element wires and made by stranding 7 stranded stranded wires each having 224 element wires and each made by stranding 7 stranded element wires each made by stranding 32 element wires, and a stranded stranded stranded wire having 2450 element wires and made by stranding 7 stranded stranded wires each having 350 element wires and each made by stranding 7 stranded element wires each made by stranding 50 element wires.
The lower limit of the average area (including spaces between the element wires) of the cross section of the conductor 2b is preferably 1.0 mm2, more preferably 1.5 mm2, still more preferably 1.8 mm2, yet still more preferably 2.0 mm2. The upper limit of the average area of the cross section of the conductor 2b is preferably 3.0 mm2, more preferably 2.8 mm2. The average area of the cross section of the conductor 2b refers to the area calculated from the average outer diameter defined as the average value of the outer diameter of the conductor 2b at freely selected three points measured by using a caliper, taking care not to deform the stranded structure under pressure.
The insulating layer 2a is composed of an insulating layer-forming composition containing a synthetic resin as a main component and disposed on the outer surface of the conductor 2b to cover the conductor 2b. The “main component” refers to a substance that is contained in the largest amount in the insulating layer 2a. The average thickness of the insulating layer 2a is not limited and is, for example, 0.1 mm to 5 mm. The “average thickness” refers to the average value of the thickness measured at freely selected ten points.
The synthetic resin, which is the main component of the insulating layer 2a, may be cross-linked by, for example, electron beam irradiation. When the main component of the insulating layer 2a is a cross-linked synthetic resin, the insulating layer 2a is unlikely to deform with heat during extrusion of the sheath layer 5 or other processes in the manufacture of the multicore cable 1. The cross-linking can be performed by exposing the insulating layer-forming composition to ionizing radiation. Examples of ionizing radiation include γ-rays, electron beams, X-rays, neutron beams, and high-energy ion beams. The lower limit of the exposure dose of ionizing radiation is preferably 10 kGy, more preferably 30 kGy. The upper limit of the exposure dose of ionizing radiation is preferably 300 kGy, more preferably 240 kGy.
Examples of the synthetic resin include polyvinyl chloride, polyolefin resins, and polyurethane resins. Examples of the polyolefin resins include polypropylene (e.g., homopolymer, block polymer, random polymer), polypropylene thermoplastic elastomer, reactor-type polypropylene thermoplastic elastomer, and dynamic cross-linked polypropylene thermoplastic elastomer; and polyethylene resins, such as polyethylene (e.g., high-density polyethylene, linear low-density polyethylene, low-density polyethylene, ultra-low-density polyethylene), ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-propylene rubber, ethylene acrylic rubber, ethylene-glycidyl methacrylate copolymer, and ethylene-methacrylic acid copolymer. Examples of the polyolefin resins further include ionomer resins in which the molecules of copolymers, such as ethylene-methacrylic acid copolymers and ethylene-acrylic acid copolymers, are bonded to each other with metal ions, such as sodium and zinc. These resins may be modified with maleic anhydride or other compounds. These resins may have an epoxy group, an amino group, an imide group, or other groups.
The lower limit of the product C×E of the coefficient of linear expansion C from −35° C. to 25° C. and the elastic modulus E at −35° C. of the insulating layer 2a is preferably 0.01 MPaK−1. The upper limit of the product C×E is preferably 0.9 MPaK−1. The product C×E can be adjusted by controlling the type and amount of synthetic resin, the presence or absence of additives, and other parameters.
The lower limit of the coefficient of linear expansion C from −35° C. to 25° C. of the insulating layer 2a is preferably 1.0×10−5 K−1, more preferably 1.0×10+K−1. The upper limit of the coefficient of linear expansion C of the insulating layer 2a is preferably 2.5×10−4 K−1, more preferably 2.0×10−4 K−1. The “coefficient of linear expansion” is a value calculated from dimensional changes of a thin plate against temperature changes measured by using a viscoelastic analyzer (“DVA-220” available from IT Keisoku Co., Ltd.) in a tensile mode in a temperature range from −100° ° C. to 200° C. at a heating rate of 5° C./min, a frequency of 10 Hz, and a strain of 0.05% in accordance with the determination of dynamic mechanical properties described in JIS-K7244-4 (1999).
The lower limit of the elastic modulus E at −35° C. of the insulating layer 2a is preferably 1,000 MPa, more preferably 2,000 MPa. The upper limit of the elastic modulus E of the insulating layer 2a is preferably 3,500 MPa, more preferably 3,000 MPa. The “elastic modulus” is a storage modulus measured by using the viscoelastic analyzer in a tensile mode in a temperature range from −100° ° C. to 200° C. at a heating rate of 5° C./min, a frequency of 10 Hz, and a strain of 0.05% in accordance with the determination of dynamic mechanical properties described in JIS-K7244-4 (1999).
The insulating layer 2a may contain additives, such as flame retardants, flame retardant aids, antioxidants, lubricants, colorants, reflection-imparting agents, masking agents, processing stabilizers, and plasticizers. Examples of flame retardants include halogenated flame retardants, such as brominated flame retardants and chlorinated flame retardants; and non-halogenated flame retardants, such as metal hydroxides, nitrogen flame retardants, and phosphorus flame retardants. Flame retardants can be used singly or in combination of two or more.
The wire 3 differs from the pair of core electric wires 2 in the core wire 4. Examples of the wire 3 include a core electric wire different from the core electric wires 2, a stranded core electric wire made by stranding multiple core electric wires, and a dummy wire, such as a resin rod.
The lower limit of the average outer diameter d2 of the wire 3 is not limited as long as the average outer diameter d2 of the wire 3 and the average outer diameter d1 of each core electric wire 2 satisfy the ratio d2/d1 in the above range. The lower limit is, for example, 1.3 mm, preferably 2.0 mm, and the upper limit is, for example, 5.0 mm, preferably 4.5 mm.
When the wire 3 is a core electric wire different from the core electric wires 2, the core electric wire preferably includes, for example, a conductor 3b and an insulating layer 3a covering the outer surface of the conductor, as shown in
When the wire 3 is a stranded core electric wire made by stranding multiple core electric wires, for example, as shown in
When the wire 3 is a dummy wire, such as a resin rod, the resin rod may be made of, for example, polyethylene or polypropylene.
The sheath layer 5 has a two-layer structure including an inner sheath layer 5a disposed on the outer side of the core wire 4 and the outer sheath layer 5b disposed on the outer surface of the inner sheath layer 5a.
The main component of the inner sheath layer 5a is any synthetic resin having flexibility. Examples of the main component of the inner sheath layer 5a include polyolefins, such as polyethylene and ethylene-vinyl acetate copolymer (EVA), polyurethane elastomers, and polyester elastomers. These compounds may be used as a mixture of two or more.
The lower limit of the minimum thickness of the inner sheath layer 5a (the minimum distance between the core wire 4 and the outer surface of the inner sheath layer 5a) is preferably 0.3 mm, more preferably 0.4 mm. The upper limit of the minimum thickness of the inner sheath layer 5a is preferably 0.9 mm, more preferably 0.8 mm.
The main component of the outer sheath layer 5b is any synthetic resin having high flame retardancy and high wear resistant. Examples of the main component of the outer sheath layer 5b include polyurethane.
The average thickness of the outer sheath layer 5b is preferably 0.3 mm to 0.7 mm.
The inner sheath layer 5a and the outer sheath layer 5b preferably each have the resin component cross-linked. The cross-linking method for the inner sheath layer 5a and the outer sheath layer 5b may be the same as the cross-linking method for the insulating layer 2a. The inner sheath layer 5a and the outer sheath layer 5b may contain the additives illustrated for the insulating layer 2a.
It is noted that a tape member, such as paper or non-woven fabric, may be wound, as a holding member, between the core wire 4 and the sheath layer 5.
The multicore cable 1 can be produced by a manufacturing method including a step of stranding a pair of core electric wires 2 and a wire 3 (stranding step) and a step of providing the sheath layer 5 for coating on the outer side of the core wire 4 made by stranding the pair of core electric wires 2 and the wire 3 (sheath layer for coating-providing step).
The method of manufacturing the multicore cable can be carried out by using, for example, a multicore cable manufacturing apparatus shown in
In the stranding step, the pair of core electric wires 2 and the wire 3 wound around the multiple supplying reels 102 are supplied to the stranding unit 103, and the pair of core electric wires 2 and the wire 3 are stranded in the stranding unit 103 to form the core wire 4.
In the sheath layer coating step, the inner sheath layer coating unit 104 extrudes a resin composition, which is used for forming the inner sheath layer and stored in a reservoir 104a, on the outer side of the core wire 4 formed in the stranding unit 103. The outer side of the core wire 4 is accordingly coated with the inner sheath layer 5a.
After the coating with the inner sheath layer 5a, the outer sheath layer coating unit extrudes a resin composition, which is used for forming the outer sheath layer and stored in a reservoir 105a, on the outer surface of the inner sheath layer 5a. The outer surface of the inner sheath layer 5a is accordingly coated with the outer sheath layer 5b.
After the coating with the outer sheath layer 5b, the sheath layer 5 is cured by cooling the core wire 4 in the cooling unit 106 to produce the multicore cable 1. The multicore cable 1 is wound and collected on the cable winding reel 107.
The method of manufacturing the multicore cable may further include a step of cross-linking the resin component of the sheath layer 5 (cross-linking step). The cross-linking step may be performed before the core wire 4 is coated with the compositions for forming the sheath layer 5 or after the coating (after the sheath layer 5 is formed).
The cross-linking can be performed in the same manner as the exposure of the insulating layer-forming composition to ionizing radiation in the insulating layer 2a of the multicore cable 1.
It should be understood that the embodiments disclosed herein are illustrative in any respect and non-restrictive. The scope of the present disclosure is not limited to the configurations of the embodiments described above, but defined by the claims and intended to include all modifications within the meaning and range of equivalency of the claims.
The sheath layer 5 of the multicore cable 1 may be a single layer or may have a multilayer structure including two or more layers.
The multicore cable 1 may include other layers between the core wire 4 and the sheath layer 5 or on the outer surface of the sheath layer 5. Examples of other layers between the core wire 4 and the sheath layer 5 include a holding member layer, such as a paper tape layer or a non-woven fabric layer. Examples of other layers disposed on the outer surface of the sheath layer 5 include a shield layer.
The present invention will be described in more detail below by way of Examples, but the present invention is not limited to these Examples.
An insulating layer-forming composition was prepared by mixing 100 parts by mass of ethylene-ethyl acrylate copolymer, 70 parts by mass of a flame retardant, and 2 parts by mass of an antioxidant, and extruded on the outer surface of a conductor (average diameter: 2.4 mm) made by stranding 7 stranded element wires each made by stranding 72 annealed copper element wires each having an average diameter of 80 μm to form an insulating layer, whereby a core electric wire having an average outer diameter d1 of 3.0 mm was produced. The insulating layer was exposed to electron beam irradiation at 60 kGy to cross-link the resin component. The ethylene-ethyl acrylate copolymer used to prepare the insulating layer-forming composition is “DPDJ-6182” (ethyl acrylate content: 15 mass %) available from ENEOS NUC Corporation, the flame retardant is aluminum hydroxide (“HIGILITE (registered trademark) H-31” available from Showa Denko K.K.), and the antioxidant is “IRGANOX (registered trademark) 1010” available from BASF.
A wire having the average outer diameter d2 shown in Table 1 below was produced by extruding cross-linked polyurethane on the outer surface of a conductor (average diameter: 0.72 mm) made by stranding 60 copper alloy element wires each having an average diameter of 80 μm to form an insulating layer.
A pair of the core electric wires produced above and the wire produced above were stranded to form a core wire, and the core wire was coated with a sheath layer by extrusion to produce multicore cables Nos. 1 to 14 having the average outer diameters D shown in Table 1 below. The sheath layer was a layer containing a cross-linked polyurethane having flame retardancy as a main component. The resin component of the sheath layer was cross-linked by electron beam irradiation at 180 kGy.
Referring to
The sheath layer of each multicore cable was cut with a V-shaped blade, and the load in removing the sheath layer was measured with a load cell. The results are shown in Table 1 below. The terminal processability was rated as “good” when the load was 40 N or less and “poor” when the load was more than 40 N.
The multicore cables were comprehensively evaluated on the basis of two items, flex resistance and terminal processability. The multicore cables were rated as “A” (good) when two items were both “good”, “B” (moderate) when one of two items was “good” and the other was “poor”, and “C” (poor) when two items were both “poor”. The multicore cables rated as “B” or higher in the comprehensive evaluation were accepted products.
Referring to Table 1, the multicore cables No. 1 to No. 3, No. 5 to No. 7, and No. 9 to No. 14 in which the ratio d2/d1 of the average outer diameter d2 of the wire to the average outer diameter d1 of each core electric wire was more than 0.5 and less than 2.0 were rated as “B” or higher in the comprehensive evaluation. The multicore cables No. 1 to No. 3, No. 5 to No. 7, No. 9, No. 10, No. 12, and No. 13 in which the ratio D/d1 of the average outer diameter D of the multicore cable to the average outer diameter d1 of each core electric wire was more than 2.7 and less than 4.0 were rated as “A” in the comprehensive evaluation.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-077349 | Apr 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/010095 | 3/8/2022 | WO |
