Core wire for multi-core cable, multi-core cable, and multi-core cable with sensor

Abstract

The multi-core cable core wire has: a conductor having multiple wires stranded together; a first insulating film covering the outer periphery of the conductor, comprising a polyethylene resin; and a second insulating film disposed in contact with the outer periphery of the first insulating film, comprising a copolymer of ethylene and an α-olefin having a carbonyl group.

Description

Technical Field

[0001] This disclosure relates to core wires for multi-core cables, multi-core cables, and multi-core cables with sensors.

[0002] This application claims priority based on Japanese Application No. 2020-145936, filed on August 31, 2020, and invokes all the contents set forth in the aforementioned Japanese application. Background Technology

[0003] In factory automation (FA), FA sensors such as photoelectric sensors and proximity sensors are used to detect position. The cable connected to the FA sensor consists of multiple core wires (insulated wires), one end of which is connected to the FA sensor. The connection between the core wires and the FA sensor is sealed with a sealing resin in a manner that includes an insulating film containing the core wires. As a cable for such applications, a type of wire (Patent Document 1) is disclosed where the end is covered with a molded resin body made of polybutylene terephthalate resin or polyamide resin.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-212224 Summary of the Invention

[0007] The multi-core cable core wire disclosed herein comprises: a conductor having a plurality of wires stranded together; a first insulating film covering the outer periphery of the conductor and comprising a polyethylene resin; and a second insulating film disposed in contact with the outer periphery of the first insulating film and comprising a copolymer of ethylene and an α-olefin having a carbonyl group. Attached Figure Description

[0008] Figure 1 This is a cross-sectional view showing the multi-core cable of the first embodiment.

[0009] Figure 2 This is a schematic diagram illustrating a multi-core cable with a sensor according to the second embodiment.

[0010] Figure 3 This is a schematic diagram of a multi-core cable with a sensor, representing a variation of the second embodiment. Detailed Implementation

[0011] [The problem this disclosure aims to solve]

[0012] Cables connected to FA sensors are sometimes used in environments with splashed oil in the factory. When oil adheres to the cable and penetrates the insulation to reach the conductor, short circuits may occur, affecting the operation of the sensor.

[0013] The purpose of this disclosure is to provide a multi-core cable core wire, a multi-core cable, and a multi-core cable with a sensor that improves oil resistance compared to previous methods.

[0014] [The Effects of This Disclosure]

[0015] According to this disclosure, it can improve oil resistance.

[0016] The following describes the implementation method.

[0017] [Description of embodiments of this disclosure]

[0018] First, embodiments of this disclosure are listed and described.

[0019] [1] A multi-core cable core wire of the present disclosure has: a conductor having a plurality of wires stranded together; a first insulating film covering the outer periphery of the conductor and comprising a polyethylene resin; and a second insulating film disposed in contact with the outer periphery of the first insulating film and comprising a copolymer of ethylene and an α-olefin having a carbonyl group.

[0020] The first insulating film comprises a polyethylene-based resin, which exhibits good oil resistance. Sometimes, sensors are connected to multi-core cables, including multi-core cable core wires, and the connection between the multi-core cable and the sensor is sealed with a sealing resin. However, good adhesion (epoxy resin adhesion) is not easily achieved between the polyethylene-based resin and the epoxy resin suitable for sealing. To address this, in one embodiment of the multi-core cable core wire of this disclosure, the second insulating film comprises a copolymer of ethylene and an α-olefin having a carbonyl group. This copolymer exhibits excellent adhesion to the epoxy resin. Therefore, while achieving good oil resistance, good adhesion to the sealing resin can be ensured.

[0021] [2] In [1], the melting point of the second insulating film may also be lower than that of the first insulating film. In this case, good bending resistance is easily obtained.

[0022] [3] In [1] or [2], the content of polyethylene resin in the first insulating film may be higher than the content of polyethylene resin in the second insulating film. In this case, good oil resistance is obtained while good adhesion to the sealing resin is easily ensured.

[0023] [4] In [1] to [3], the average thickness of the first insulating film may also be greater than or equal to the average thickness of the second insulating film. In this case, good oil resistance is obtained while good adhesion to the sealing resin is easily ensured.

[0024] [5] In [1] to [4], the α-olefin having a carbonyl group may also constitute 9% by mass or more and 33% by mass or less in the copolymer. In this case, good mechanical properties are readily obtained while ensuring good adhesion to the sealing resin.

[0025] [6] In [1] to [5], the polyethylene resin may also account for 30% or more of the resin component contained in the first insulating film. In this case, better oil resistance is easily obtained.

[0026] [7] In [1] to [6], the melting point of the first insulating film may also be above 110°C and below 140°C. In this case, better oil resistance is easily obtained.

[0027] [8] In [1] to [7], the second insulating film may also contain an ethylene-vinyl acetate copolymer as the copolymer. In this case, better adhesion to the sealing resin is easily ensured.

[0028] [9] In [8], the resin component contained in the second insulating film may also be solely ethylene-vinyl acetate copolymer. In this case, particularly good adhesion to the sealing resin is easily ensured.

[0029]

[10] Another aspect of this disclosure is a multi-core cable core wire comprising: a conductor having a plurality of wires stranded together; a first insulating film covering the outer periphery of the conductor and comprising a polyethylene resin; and a second insulating film disposed in contact with the outer periphery of the first insulating film and comprising a copolymer of ethylene and vinyl acetate, wherein the vinyl acetate comprises 9% by mass or more and 33% by mass or less in the copolymer, the average thickness of the first insulating film is greater than or equal to the average thickness of the second insulating film, and the polyethylene resin comprises 30% by mass or more in the resin component contained in the first insulating film.

[0030] Multi-core cables include a first insulating film and a second insulating film with appropriately defined components, thus achieving better oil resistance while ensuring better adhesion to the sealing resin.

[0031]

[11] Another aspect of the multi-core cable disclosed herein comprises: core wires, wherein a plurality of core wires are stranded together; and a sheath layer disposed around the core wires, wherein at least one of the plurality of core wires is a multi-core cable core wire of [1] to

[10] . In this case, good oil resistance is achieved in the multi-core cable, while good adhesion to the sealing resin is ensured.

[0032]

[12] Another aspect of this disclosure provides a sensor-equipped multi-core cable comprising:

[11] the multi-core cable; and a sensor connected to the conductors of the plurality of core wires exposed from the first and second insulating films, the sensor-equipped multi-core cable comprising: a sealing resin for sealing the portions of the conductors exposed from the first and second insulating films. In this case, good oil resistance is achieved in the sensor-equipped multi-core cable, while ensuring good adhesion between the multi-core cable and the sealing resin.

[0033] [Details of the embodiments disclosed herein]

[0034] The embodiments of this disclosure will be described in detail below, but the embodiments are not limited thereto. It should be noted that in this specification and drawings, for constituent elements having substantially the same functional configuration, repeated descriptions are sometimes omitted by using the same reference numerals.

[0035] (First Implementation)

[0036] The first embodiment relates to a multi-core cable. Hereinafter, it will be described based on a cross-sectional view orthogonal to the longitudinal direction of the multi-core cable. Figure 1 This is a cross-sectional view showing the multi-core cable of the first embodiment. Figure 1 A cross-section orthogonal to the long dimension of the multi-core cable is shown.

[0037] The multi-core cable 1 of the first embodiment has core wires 30 and a sheath layer 40 disposed around the core wires 30. The multi-core cable 1 is suitable for use as a cable for connecting to an FA sensor. The multi-core cable 1 can also be used as an automotive cable.

[0038] The average outer diameter of the multi-core cable 1 is appropriately designed according to its application, but the lower limit of the average outer diameter is preferably 2.0 mm, more preferably 3.0 mm. On the other hand, the upper limit of the average outer diameter of the multi-core cable 1 is preferably 7.0 mm, more preferably 6.0 mm. The average outer diameter of the multi-core cable 1 can be determined as follows: the outer diameter of any three equally spaced points along the circumference of the multi-core cable 1 is measured using vernier calipers, and the average value of these measurements is taken as the average outer diameter.

[0039] <Core Wire>

[0040] The core wire 30 is formed by twisting two core wires 10 of equal diameter together.

[0041] <Multi-core cable core wire>

[0042] The core wire 10 has a linear conductor 11 and an insulation layer 12 covering the outer periphery of the conductor 11. The core wire 10 is an example of a core wire for a multi-core cable.

[0043] The cross-sectional shape of the core wire 10 is not particularly limited, and for example, it is set to be circular. When the cross-sectional shape of the core wire 10 is set to be circular, its average outer diameter varies depending on the use, and for example, it can be set to be 0.6 mm or more and 2.0 mm or less. The average outer diameter of the cross-section of the core wire 10 can be determined as follows. That is, measure the outer diameters of any three points at equal intervals in the circumferential direction of the core wire 10 using a vernier caliper, and set the average value thereof as the average outer diameter.

[0044] <Conductor>

[0045] The conductor 11 is formed by stranding a plurality of wire materials at a fixed pitch. There is no particular limitation on the wire material, and for example, soft copper wire, copper alloy wire, copper-clad steel wire, tinned copper wire, aluminum wire, aluminum alloy wire, etc. can be cited. In addition, it is preferable that the conductor 11 is a secondary stranded wire (referred to as a twisted wire in Japanese) formed by further stranding a plurality of stranded wire materials obtained by stranding a plurality of wire materials. Preferably, the stranded wire materials to be stranded are stranded from the same number of wire materials. The conductor 11 is, for example, any type among AWG20 to AWG30.

[0046] The number of wire materials is appropriately designed according to the use of the multi-core cable, the diameter of the wire materials, etc. As the lower limit, it is preferably 196, and more preferably 294. On the other hand, the upper limit of the number of wire materials is preferably 2450, and more preferably 2000. In addition, as examples of the secondary stranded wire, there can be cited: a secondary stranded wire having 196 wire materials, which is formed by further stranding the stranded wire materials obtained by stranding 7 strands of 28 wire materials; a secondary stranded wire having 294 wire materials, which is formed by further stranding the stranded wire materials obtained by stranding 7 strands of 42 wire materials; a secondary stranded wire having 380 wire materials, which is formed by further stranding the stranded wire materials obtained by stranding 19 strands of 20 wire materials; a tertiary stranded wire (referred to as a twisted wire in Japanese) having 1568 wire materials, which is formed by further stranding 7 secondary stranded wires each having 224 wire materials, and the secondary stranded wire is formed by further stranding the stranded wire materials obtained by stranding 7 strands of 32 wire materials; a tertiary stranded wire having 2450 wire materials, which is formed by further stranding 7 secondary stranded wires each having 350 wire materials, and the secondary stranded wire is formed by further stranding the stranded wire materials obtained by stranding 7 strands of 50 wire materials; etc.

[0047] The lower limit of the average diameter of the wire material is preferably 30 μm, and more preferably 40 μm. On the other hand, the upper limit of the average diameter of the wire material is preferably 320 μm, and more preferably 260 μm. When the average diameter of the wire material is less than the above lower limit or exceeds the above upper limit, it is feared that sufficient bending resistance for the core wire 10 cannot be obtained. The average diameter of the wire material can be determined as follows. That is, measure the diameters of any three points at equal intervals in the circumferential direction of the wire material using a micrometer with cylindrical ends at both ends, and set the average value thereof as the average diameter.

[0048] <Insulation layer>

[0049] The insulating layer 12 has: a first insulating film 21 covering the outer periphery of the conductor 11; and a second insulating film 22 configured to be in contact with the outer periphery of the first insulating film 21.

[0050] <First Insulating Film>

[0051] The first insulating film 21 comprises a polyethylene (PE) based resin. Examples of polyethylene based resins include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ethylene-alpha-olefin copolymers. Furthermore, examples of polyethylene based resins such as ethylene-alpha-olefin copolymers include ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EMA), and ethylene-butyl acrylate copolymer (EBA). Low-density polyethylene and linear low-density polyethylene are preferred among these. One or more of these polyethylene based resins can be used. When two or more polyethylene based resins are used in combination, the two or more polyethylene based resins may constitute the main component of the first insulating film 21. When using two or more polyethylene based resins, in order to consider properties such as elastic modulus at low and high temperatures, combinations of high-density polyethylene (HDPE) and low-density polyethylene (LDPE), HDPE and linear low-density polyethylene (LLDPE), and HDPE and EVA are preferred.

[0052] In addition to PE resin, the first insulating film 21 may also contain additives such as flame retardants, flame retardant auxiliaries, antioxidants, lubricants, colorants, reflective agents, masking agents, processing stabilizers, and plasticizers.

[0053] Examples of flame retardants include halogenated flame retardants such as brominated and chlorinated flame retardants, as well as halogen-free flame retardants such as metal hydroxides, nitrogen-based flame retardants, and phosphorus-based flame retardants. Flame retardants can be used alone or in combination of two or more. Examples of brominated flame retardants include decabromodiphenyl ethane. Examples of chlorinated flame retardants include chlorinated paraffin, chlorinated polyethylene, chlorinated polyphenols, and perchloropentacyclodecane. Examples of metal hydroxides include magnesium hydroxide and aluminum hydroxide. Examples of nitrogen-based flame retardants include melamine cyanurate, triazine, isocyanurate, urea, and guanidine. Examples of phosphorus-based flame retardants include metal phosphonates, phenanthrene phosphate, melamine phosphate, ammonium phosphate, phosphate esters, and polyphosphazenes. From the viewpoint of reducing environmental impact, halogen-free flame retardants are preferred, and metal hydroxides, nitrogen-based flame retardants, and phosphorus-based flame retardants are more preferred.

[0054] The first insulating film 21 may contain other resins as resin components besides PE-based resin. However, it is preferable that the first insulating film 21 contains 30% by mass or more of PE-based resin as a resin component. That is, the proportion of PE-based resin in the resin component contained in the first insulating film 21 is preferably 30% by mass or more. When the proportion of PE-based resin is less than 30% by mass, sufficient oil resistance may not be obtained. The upper limit of the content of other resins is preferably 70% by mass, more preferably 50% by mass, and even more preferably 30% by mass. The first insulating film 21 may also substantially not contain other resins as resin components. The proportion of PE-based resin in the resin component contained in the first insulating film 21 can be determined by the ratio of the heat of fusion of the crystal by differential scanning calorimetry.

[0055] The lower limit of the melting point of the first insulating film 21 is preferably 110°C, more preferably 115°C. On the other hand, the upper limit of the melting point of the first insulating film 21 is preferably 140°C, more preferably 135°C. When the melting point of the first insulating film 21 is lower than 110°C, the melting point is lower than the operating environment, and it may not be possible to obtain sufficient mechanical properties such as wear resistance and strength in a temperature range above room temperature. When the melting point of the first insulating film 21 exceeds 140°C, the first insulating film 21 is prone to fatigue failure, and cracks may occur, making it impossible to obtain sufficient bending performance (bending resistance).

[0056] The melting point of the first insulating film 21 can be determined by differential scanning calorimetry (DSC). That is, using a differential scanning calorimeter, under the condition of a heating rate of 10℃ / min, the endothermic peak temperature at the second heating when the temperature of the sample changes in the order of 25℃→200℃→25℃→200℃ is set as the melting point of the sample.

[0057] The lower limit of the average thickness of the first insulating film 21 is preferably 0.08 mm, more preferably 0.150 mm, and even more preferably 0.20 mm. On the other hand, the upper limit of the average thickness of the first insulating film 21 is preferably 0.60 mm, more preferably 0.50 mm, and even more preferably 0.30 mm. When the average thickness of the first insulating film 21 is less than 0.08 mm, sufficient oil resistance may not be obtained. When the average thickness of the first insulating film 21 exceeds 0.60 mm, sufficient bending resistance may not be obtained. The average thickness of the first insulating film 21 can be determined as follows: the thickness of ten equally spaced points along the circumference of the first insulating film 21 is measured using vernier calipers, and the average value of these measurements is taken as the average thickness.

[0058] <Second Insulating Film>

[0059] The second insulating film 22 comprises a copolymer of ethylene and an α-olefin having a carbonyl group. Examples of α-olefins having a carbonyl group include alkyl (meth)acrylates, aryl (meth)acrylates, vinyl esters, unsaturated acids, vinyl ketones, and (meth)acrylamide. Examples of alkyl (meth)acrylates include methyl (meth)acrylate and ethyl (meth)acrylate. Examples of aryl (meth)acrylates include phenyl (meth)acrylate. Examples of vinyl esters include vinyl acetate and vinyl propionate. Examples of unsaturated acids include (meth)acrylic acid, crotonic acid, maleic acid, and itaconic acid. Examples of vinyl ketones include methyl vinyl ketone and phenyl vinyl ketone. Alkyl (meth)acrylates and vinyl esters are preferred, and ethyl acrylate and vinyl acetate are more preferred. Resins such as EVA, EEA, EMA, and EBA can be used as copolymers, with EVA and EEA being preferred. This is because excellent oil resistance is easily obtained.

[0060] The lower limit of the proportion of the carbonyl-containing α-olefin in the above copolymer is preferably 9% by mass, more preferably 12% by mass. On the other hand, the upper limit of this proportion is preferably 33% by mass, more preferably 25% by mass. When this proportion is less than 9% by mass, sufficient adhesion may not be obtained between the epoxy resin suitable for sealing and the second insulating film 22. When this proportion exceeds 33% by mass, the mechanical properties of the second insulating film 22, such as tensile strength, may decrease. The proportion of the carbonyl-containing α-olefin can be determined by the intensity of the absorption peak of the carbonyl group in the infrared absorption spectrum.

[0061] In addition to the copolymers mentioned above, the second insulating film 22 may also contain additives such as flame retardants, flame retardant auxiliaries, antioxidants, lubricants, colorants, reflective agents, masking agents, processing stabilizers, and plasticizers, just like the first insulating film 21.

[0062] In addition to the copolymer described above, the second insulating film 22 may also contain other resins as resin components. However, it is preferable that the second insulating film 22 contains 50% by mass or more of the copolymer as a resin component. That is, the proportion of the copolymer in the resin component of the second insulating film 22 is preferably 50% by mass or more. When the proportion of the copolymer is less than 50% by mass, sufficient adhesion to the epoxy resin may not be achieved. The upper limit of the content of other resins is preferably 50% by mass, more preferably 30% by mass, and even more preferably 10% by mass. The second insulating film 22 may also substantially not contain other resins as resin components. The second insulating film 22 may contain more than 60% by mass of EVA as a resin component, or it may contain only EVA as a resin component. That is, the second insulating film 22 may also not contain PE resin, and the content of PE resin in the first insulating film 21 may be higher than the content of PE resin in the second insulating film 22. When the content of PE resin in the first insulating film 21 is less than the content of PE resin in the second insulating film 22, sufficient oil resistance and adhesion to the epoxy resin may not be achieved. The proportions of the other resins mentioned above can be determined by the ratio of the heat of melting of the crystals using differential scanning calorimetry.

[0063] The resin component of the second insulating film 22 can also be crosslinked. Methods for crosslinking the resin component of the second insulating film 22 include irradiation with ionizing radiation, the use of a thermal crosslinking agent, and the use of a silane graft polymer; irradiation with ionizing radiation is preferred. Furthermore, to promote crosslinking, it is preferable to add a silane coupling agent to the composition constituting the second insulating film 22.

[0064] Preferably, the melting point of the second insulating film 22 is lower than that of the first insulating film 21. Generally, the lower the melting point of the resin, the easier it is to bend. Since the second insulating film 22, located on the outer side, is easy to bend, its bending resistance is easily improved. The melting point of the second insulating film 22 can also be determined by differential scanning calorimetry in the same way as the melting point of the first insulating film 21.

[0065] The lower limit of the average thickness of the second insulating film 22 is preferably 0.08 mm, more preferably 0.09 mm. On the other hand, the upper limit of the average thickness of the second insulating film 22 is preferably 0.12 mm, more preferably 0.11 mm. When the average thickness of the second insulating film 22 is less than 0.08 mm, sufficient adhesion to the epoxy resin may not be achieved. When the upper limit of the average thickness of the second insulating film 22 exceeds 0.12 mm, the diameter of the core wire 10 may become excessive. The average thickness of the second insulating film 22 can be determined as follows: the thickness of ten equally spaced points along the circumference of the second insulating film 22 is measured using vernier calipers, and the average value of these measurements is taken as the average thickness.

[0066] Furthermore, it is preferable that the average thickness of the first insulating film 21 is greater than or equal to the average thickness of the second insulating film 22. More preferably, the average thickness of the first insulating film 21 is greater than the average thickness of the second insulating film 22. A thicker first insulating film 21 results in higher oil resistance, but the thickness of the second insulating film 22 has little effect on adhesion to the epoxy resin. To avoid excessive thickness of the insulating layer 12 and to obtain adequate oil resistance and adhesion, it is preferable that the average thickness of the first insulating film 21 is greater than or equal to the average thickness of the second insulating film 22. The lower limit of the ratio of the average thickness of the first insulating film 21 to the average thickness of the second insulating film 22 is preferably 2.0, more preferably 2.2. On the other hand, the upper limit of this ratio is preferably 3.0, more preferably 2.8.

[0067] <Sheath layer>

[0068] As the main component of the sheath layer 40, there are no particular limitations as long as it is a synthetic resin with excellent flame retardancy and abrasion resistance; examples include polyvinyl chloride (PVC) and polyurethane. The outer diameter of the sheath layer is, for example, about 0.25 mm to 1.2 mm. The resin components in the sheath layer can also be cross-linked. The cross-linking method of the sheath layer can be the same as the cross-linking method of the second insulating film 22.

[0069] The sheath layer can also have a double-layer structure, such as an inner sheath layer stacked on the outside of the core wire 30 and an outer sheath layer stacked on the outer periphery of the inner sheath layer. Examples of main components of the inner sheath layer include polyethylene, polyolefins such as EVA, polyurethane elastomers, and polyester elastomers. Two or more of the above materials can also be used in combination. Examples of main components of the outer sheath layer include PVC and polyurethane. For example, the outer diameter of the outer sheath layer is approximately 1 to 3 times that of the inner sheath layer.

[0070] In both the inner and outer sheath layers, the resin components can also be cross-linked. The cross-linking method for the inner and outer sheath layers can be the same as that for the second insulating film 22.

[0071] The sheath layer 40 may also contain the same additives as the second insulating film 22.

[0072] It should be noted that paper or other tape components can also be wound between the sheath layer 40 and the core wire 30 as a compression component.

[0073] In the multi-core cable 1 of the first embodiment, the first insulating film 21 comprises a polyethylene-based resin, which has good oil resistance. Furthermore, the second insulating film 22 comprises a copolymer of EVA, ethylene, and an α-olefin having a carbonyl group. This copolymer exhibits excellent adhesion to the epoxy resin used as the sealing resin. Therefore, when an epoxy resin is used as the sealing resin, the intrusion of liquids such as oil and water into the sensor via the interface between the core wire 10 and the sealing resin can be prevented.

[0074] It should be noted that, preferably, all of the multiple core wires 10 included in the multi-core cable 1 have the above-described configuration, but it is sufficient for at least one core wire 10 to have the above-described configuration.

[0075] (Second Implementation)

[0076] The second embodiment involves a multi-core cable with a sensor. Figure 2 This is a schematic diagram illustrating a multi-core cable with a sensor according to the second embodiment.

[0077] The second embodiment of the multi-core cable 2 with sensor includes a multi-core cable 1, a sensor 51, and a sealing resin 52. The sensor 51 is connected to the conductors 11 of the multiple core wires 10 exposed from the first insulating film 21 and the second insulating film 22. The sealing resin 52 seals the portions of the conductors 11 exposed from the first insulating film 21 and the second insulating film 22. That is, at one end of two core wires 10 included in the multi-core cable 1, the insulation layer 12 is peeled off, exposing the conductor 11, and the sensor 51 is connected to the portion of the conductor 11 exposed from the insulation layer 12. Furthermore, the portion of the conductor 11 exposed from the insulation layer 12 and the sensor 51 are sealed by the sealing resin 52.

[0078] The sealing resin 52 is, for example, a polyimide-based resin. In the second embodiment, the sealing resin 52 is configured to be separate from the sheath layer 40 and in contact with the outer periphery of the second insulating film 22.

[0079] The second insulating film 22 comprises a copolymer of EVA, ethylene, and an α-olefin having a carbonyl group. This copolymer exhibits excellent adhesion to the epoxy resin. Therefore, it can prevent liquids such as oil and water from entering the sensor 51 through the interface between the core wire 10 and the sealing resin 52. Furthermore, good oil resistance is achieved through the first insulating film 21.

[0080] (A variation of the second embodiment)

[0081] The main difference between the second embodiment and the second embodiment lies in the range of the sealing resin. Figure 3 This is a schematic diagram of a multi-core cable with a sensor, representing a variation of the second embodiment.

[0082] like Figure 3 As shown, in a modified example of the second embodiment, the multi-core cable 3 with sensor has a sealing resin 53 instead of a sealing resin 52. The sealing resin 53 seals the portions of the conductor 11 exposed from the first insulating film 21 and the second insulating film 22 in the same way as the sealing resin 52.

[0083] The sealing resin 53 is, for example, a polyimide-based resin. In a variation of the second embodiment, the sealing resin 53 is configured to be in contact not only with the outer periphery of the second insulating film 22, but also with the outer periphery of the sheath layer 40.

[0084] The other components are the same as in the second embodiment.

[0085] Through such a variation, the same effect as the second embodiment can be obtained.

[0086] Here, an experimental example is described. In this experimental example, a sample of a multi-core cable having core wires and a sheath layer disposed around the core wires, as in the first embodiment, was fabricated. In the fabrication of each sample, a stranded wire obtained by twisting seven wires with an outer diameter of 0.2 mm was used as the conductor. A first insulating film and a second insulating film, as shown in Table 1, were formed around the conductor by extrusion molding, thereby producing the core wires. Furthermore, a sheath layer was disposed around the two core wires, thereby forming a multi-core cable. PVC was used as the material for the sheath layer, and the thickness of the sheath layer was set to 1.0 mm. Details of the various materials in Table 1 are shown in Tables 2 and 3.

[0087] [Table 1]

[0088]

[0089] [Table 2]

[0090]

[0091] 1) NOVATEC HB530, manufactured by Japan Polyethylene Co., Ltd. (melting point 136℃)

[0092] 2) NOVATEC HB420R, manufactured by Japan Polyethylene Co., Ltd. (melting point 133℃)

[0093] 3) NOVATEC UE320, manufactured by Japan Polyethylene Co., Ltd. (melting point 122℃)

[0094] 4) NOVATEC ZE41K, manufactured by Japan Polyethylene Co., Ltd. (melting point 111℃)

[0095] 5) ENGAGE8540, manufactured by Dow Chemical Company (melting point 104°C)

[0096] 6) SUNTEC EF0510, manufactured by Asahi Kasei Corporation (VA content 4.8%, melting point 103℃)

[0097] 7) SUNTEC EF0910, manufactured by Asahi Kasei Corporation (VA content 9%, melting point 97°C)

[0098] 8) SUNTEC EF1510, manufactured by Asahi Kasei Corporation (VA content 15%, melting point 89°C)

[0099] 9) EVAFLEX EV170, manufactured by Mitsui-DuPont Polymer Chemicals Co., Ltd. (VA content 33%, melting point 62°C)

[0100] 10) EVAFLEX EV40LX, manufactured by Mitsui-DuPont Polymer Chemicals Co., Ltd. (VA content 40%, melting point 40°C)

[0101] 11)ZEST1300Z Made by New Daiichi PVC Co., Ltd.

[0102] 12) Saytex 8010, a brominated flame retardant manufactured by Albemarle.

[0103] 13) PATOX-M, manufactured by Nippon Minerals Co., Ltd., is a type of antimony trioxide.

[0104] 14) IRGANOX 1010 (Made by BASF)

[0105] 15)TD1500s Trimethylolpropane trimethacrylate manufactured by DIC Co., Ltd.

[0106] 16)DINP J-PLUS Co., Ltd.

[0107] 17)RUP151 Made by ADEKA Co., Ltd.

[0108] [Table 3]

[0109]

[0110] The average thickness ratio in Table 1 is the ratio of the average thickness of the first insulating film to the average thickness of the second insulating film. The components in Tables 2 and 3 are in parts by mass. The VA ratio of EVA is the proportion (by mass%) of vinyl acetate (VA) in the EVA. The melting points of the various materials are values ​​determined by the DSC described above.

[0111] Furthermore, the oil resistance, epoxy resin adhesion, and strength of each multi-core cable were evaluated.

[0112] The oil resistance was evaluated according to JIS C 3005. Specifically, in the oil resistance evaluation, each multi-core cable was immersed in water-soluble cutting oil (EMULCUT DC-60N) at 50°C for 60 days, and then removed from the water-soluble cutting oil. Next, while keeping one end of the multi-core cable unimmersed, it was immersed in tap water, and the insulation resistance between the core wires and the tap water was measured. The results are shown in Table 4. In Table 4, samples with an insulation resistance of 100 MΩ·km or higher are designated as A, samples with an insulation resistance of 10 MΩ·km or higher but less than 100 MΩ·km are designated as B, and samples with an insulation resistance less than 10 MΩ·km are designated as C.

[0113] In the evaluation of epoxy resin adhesion, at one end of a multi-core cable, the second insulation film was exposed by peeling off the sheath layer, and then the conductor was exposed by peeling off a portion of the second and first insulation films. The length of the peeled portion of the sheath layer was 20 mm, and the length of the peeled portions of the second and first insulation films was 5 mm. Next, the exposed conductor and second insulation film were coated with epoxy resin (Stycast 2850FTJ (Emerson & Cuming curing agent catalyst 9M)) and the epoxy resin was cured. Afterward, the epoxy resin-coated portion (the end) was subjected to thermal shock at temperatures ranging from -30°C to 80°C. That is, the end was repeatedly heated to 80°C and cooled to -30°C. Furthermore, every 10 cycles, the end was immersed in tap water, and the insulation resistance between the conductor and tap water was measured. The number of cycles required for the insulation resistance to become less than 1% of its initial value was determined. The results are shown in Table 4. In Table 4, samples with more than 500 cycles are designated as A, samples with more than 100 cycles but less than 500 cycles are designated as B, and samples with less than 100 cycles are designated as C.

[0114] For the strength evaluation, tensile tests were conducted according to JIS C 3005 to determine the tensile strength. The results are shown in Table 4. In Table 4, samples with a tensile strength of 10 MPa or higher are designated as A, and samples with a tensile strength of less than 10 MPa are designated as B.

[0115] [Table 4]

[0116]

[0117] As shown in Table 4, sample A has low oil resistance, and sample B has low epoxy resin adhesion.

[0118] Among samples C, D, E, F, and G, samples E, F, and G exhibit particularly excellent epoxy resin adhesion.

[0119] Among samples H, I, J, and K, samples I, J, and K exhibit particularly excellent epoxy resin adhesion.

[0120] Among samples L, M, N, O, and P, samples L, M, N, and O exhibited particularly excellent oil resistance.

[0121] Among samples Q, R, and S, sample Q exhibits particularly excellent oil resistance.

[0122] Among samples T, U, V, and W, samples U, V, and W exhibit particularly excellent oil resistance, while samples T, U, and V demonstrate particularly excellent epoxy resin adhesion.

[0123] The embodiments have been described in detail above, but the present invention is not limited to the specific embodiments, and various modifications and alterations can be made within the scope of the claims.

[0124] Explanation of reference numerals in the attached figures

[0125] 1: Multi-core cable;

[0126] 2, 3: Multi-core cable with sensor;

[0127] 10-core wire;

[0128] 11: Conductor;

[0129] 12: Insulation layer;

[0130] 21: First insulating film;

[0131] 22: Second insulating film;

[0132] 30: Core wire;

[0133] 40: Sheath layer;

[0134] 51: Sensor;

[0135] 52, 53: Sealing resin.

Claims

1. A core wire for multi-core cables, comprising: A conductor, consisting of multiple strands of wire; A first insulating film, covering the outer periphery of the conductor, comprises a polyethylene resin; as well as The second insulating film, configured to be in contact with the outer periphery of the first insulating film, comprises a copolymer of ethylene and an α-olefin having a carbonyl group. The average thickness of the first insulating film is greater than or equal to the average thickness of the second insulating film, and the average thickness of the first insulating film is greater than or equal to 0.11 mm. The polyethylene resin accounts for more than 30% by mass of the resin components contained in the first insulating film. The melting point of the first insulating film is above 110°C and below 140°C. The copolymer constitutes 50% or more of the resin composition of the second insulating film by mass, and the other resins constitute 30% or less of the resin composition of the second insulating film by mass. The melting point of the second insulating film is lower than that of the first insulating film.

2. The core wire for multi-core cables according to claim 1, wherein, The content of polyethylene resin in the first insulating film is higher than that in the second insulating film.

3. The core wire for multi-core cables according to claim 1 or 2, wherein, The α-olefin having a carbonyl group accounts for more than 9% by mass and less than 33% by mass in the copolymer.

4. The core wire for multi-core cables according to claim 1 or 2, wherein, The second insulating film contains an ethylene-vinyl acetate copolymer as the copolymer.

5. The core wire for a multi-core cable according to claim 4, wherein, The resin component contained in the second insulating film is only ethylene-vinyl acetate copolymer.

6. A core wire for a multi-core cable, comprising: A conductor, consisting of multiple strands of wire; A first insulating film, covering the outer periphery of the conductor, comprises a polyethylene resin; and The second insulating film, configured to be in contact with the outer periphery of the first insulating film, comprises a copolymer of ethylene and vinyl acetate. The vinyl acetate comprises 12% by mass or more and 25% by mass or less in the copolymer. The average thickness of the first insulating film is greater than or equal to the average thickness of the second insulating film, and the average thickness of the first insulating film is greater than or equal to 0.11 mm. The polyethylene resin accounts for more than 30% by mass of the resin components contained in the first insulating film. The melting point of the first insulating film is above 110°C and below 140°C. The copolymer constitutes 50% or more of the resin composition of the second insulating film by mass, and the other resins constitute 30% or less of the resin composition of the second insulating film by mass. The melting point of the second insulating film is lower than that of the first insulating film.

7. A multi-core cable, comprising: Core wire, consisting of multiple stranded wires; and A sheath layer is disposed around the core wire. At least one of the plurality of core wires is a core wire for a multi-core cable as described in any one of claims 1 to 6.

8. A multi-core cable with a sensor, comprising: The multi-core cable as described in claim 7; and The sensor is connected to the conductors of the plurality of core wires exposed from the first and second insulating films. The multi-core cable with sensor has a sealing resin for sealing the portion of the conductor exposed from the first insulating film and the second insulating film.

Images