Multi-core cables and harnesses

Abstract

The multicore cable comprises a plurality of coated electrical wires and a second coating layer covering the outer periphery of the plurality of the coated electrical wires. Each of the coated electrical wires comprises a conductor and a first coating layer covering the conductor. The first coating layer is a cross-linked fluoroelastomer or a cross-linked fluorine resin. The second coating layer is a cross-linked fluoroelastomer.

Description

[Technical field]

[0001] The present disclosure relates to a multi-conductor cable and harness.

[0002] This application claims priority to Japanese Application No. 2019-158559, filed on August 30, 2019, and incorporates by reference all of the contents of said Japanese application. [Background technology]

[0003] For example, Patent Document 1 discloses an insulated electric wire having a conductor and an insulator covering the outer periphery of the conductor, the cross-sectional area of ​​the conductor being 0.4 mm 2 The insulator contains a polymer having S or F in the main chain, has a thickness of 0.05 mm or more, and has a wire density of 3.1 g / cm 3 Thus, an insulated wire is disclosed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-183173 A Summary of the Invention

[0005] The multi-core cable of the present disclosure includes a plurality of covered electric wires and a second covering layer covering the outer circumference of the plurality of covered electric wires, The coated electric wire includes a conductor and a first coating layer that covers the conductor. the first coating layer is a crosslinked fluoroelastomer or a crosslinked fluororesin, The second coating layer is a crosslinked fluoroelastomer. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view of a multi-core cable according to one embodiment of the present disclosure taken along a plane perpendicular to the longitudinal direction. [Diagram 2]FIG. 2 is a side view of a harness according to one embodiment of the present disclosure. [Diagram 3] FIG. 3 is an explanatory diagram of the adhesion test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] [Problem that this disclosure aims to solve] There was a demand for multi-core cables that could be used in devices inside automobiles or for wiring between devices, allowing multiple terminals to be connected with a single cable. Furthermore, because temperatures can reach high levels inside an automobile, for example around the engine, and because cables may come into contact with various chemicals such as oil, there was a demand for multi-core cables that were particularly resistant to heat and chemicals.

[0008] Therefore, an object of the present disclosure is to provide a multi-core cable that is heat-resistant and chemical-resistant.

[0009] [Effects of this disclosure] According to the present disclosure, a multi-core cable having heat resistance and chemical resistance can be provided.

[0010] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be described. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description thereof will not be repeated.

[0011] (1) A multi-core cable according to one embodiment of the present disclosure includes a plurality of covered electric wires and a second covering layer covering an outer periphery of the plurality of covered electric wires, The coated electric wire includes a conductor and a first coating layer that covers the conductor. the first coating layer is a crosslinked fluoroelastomer or a crosslinked fluororesin, The second coating layer is a crosslinked fluoroelastomer.

[0012] A multi-core cable according to an embodiment of the present disclosure has two resin layers covering a conductor: a first covering layer included in the covered electric wire, and a second covering layer covering a plurality of covered electric wires.

[0013] Furthermore, by using cross-linked materials for both the first and second coating layers, the decomposition temperature becomes high, making it possible to provide a multi-core cable with excellent heat resistance.

[0014] In addition, since the cross-linked fluororesin and the cross-linked fluoroelastomer are both fluorine-based resins and elastomers, they also have excellent chemical resistance. Therefore, by making a multi-core cable having such a first covering layer and a second covering layer, it is possible to make the multi-core cable excellent in chemical resistance.

[0015] The first coating layer can be made of a crosslinked fluoroelastomer or a crosslinked fluororesin, and when the first coating layer is made of a crosslinked fluororesin, the layer has particularly high hardness. Therefore, when the first coating layer is made of a crosslinked fluororesin, the internal conductor can be particularly prevented from being crushed and broken even when an external force is applied to the multi-core cable.

[0016] Since cross-linked fluoroelastomers are softer than cross-linked fluororesin, using a cross-linked fluoroelastomer for the second coating layer, which is the outer periphery of a multi-core cable, can improve the handleability of the multi-core cable.

[0017] (2) The adhesive strength of the second coating layer to the first coating layer per 35 mm length may be 20 N or more and 150 N or less.

[0018] By setting the adhesion strength of the second coating layer to the first coating layer per 35 mm length to 150 N or less, the second coating layer can be easily peeled from multiple coated electric wires, thereby improving the workability when connecting a connector, etc. to the end of a multi-core cable.

[0019] By setting the adhesion of the second coating layer to the first coating layer per 35 mm length to 20 N or more, the adhesion of the second coating layer to the multiple coated electric wires can be sufficiently increased, and chemical resistance can be particularly improved.

[0020] (3) A lubricant may be disposed between the first coating layer and the second coating layer.

[0021] By disposing a lubricant between the first and second coating layers, the adhesion of the second coating layer to the first coating layer can be adjusted. By disposing a lubricant, the second coating layer can be more easily peeled off from the coated electric wire, and the workability can be improved when connecting a connector or the like to the end of the multi-core cable.

[0022] (4) The plurality of covered electric wires may be twisted together, and the twist pitch may be 5 mm or more and 60 mm or less.

[0023] By setting the twist pitch of the multiple covered electric wires to 60 mm or less, the adhesive strength of the second covering layer to the multiple covered electric wires can be sufficiently increased, and the chemical resistance and noise resistance can be particularly improved.

[0024] By setting the twist pitch of the multiple insulated electric wires to 5 mm or more, it is possible to improve the peelability of the second coating layer from the multiple insulated electric wires, thereby improving the workability when connecting a connector or the like to the end of the multi-core cable. It is also possible to improve the productivity when twisting multiple insulated electric wires.

[0025] (5) The second coating layer may have a thickness of 0.1 mm or more and 0.6 mm or less.

[0026] By making the thickness of the second coating layer 0.1 mm or more, the coated electric wire can be adequately protected and durability can be increased. By making the thickness of the second coating layer 0.6 mm or less, the multi-core cable can be easily bent and made lighter. In addition, the cord diameter of the multi-core cable can be made smaller, so the space required to install the multi-core cable can be reduced.

[0027] (6) A harness according to one embodiment of the present disclosure includes a multi-core cable according to any one of (1) to (5), and connectors disposed at both longitudinal ends of the multi-core cable.

[0028] The harness according to one embodiment of the present disclosure uses the multi-core cable described above, and therefore has excellent heat resistance and chemical resistance. In addition, since the multi-core cable has multiple covered electric wires, multiple terminals can be connected simultaneously, and wiring can be easily performed.

[0029] [Details of the embodiment of the present disclosure] Specific examples of a multi-core cable and harness according to an embodiment of the present disclosure (hereinafter referred to as the present embodiment) will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. 1. Multi-core cable As shown in FIG. 1, the multi-core cable 10 of this embodiment includes a plurality of coated electric wires 11 and a second coating layer 12 covering the outer circumference of the plurality of coated electric wires 11, and the coated electric wires 11 may include a conductor 111 and a first coating layer 112 covering the conductor 111.

[0030] The first coating layer 112 can be a cross-linked fluoroelastomer or a cross-linked fluororesin, and the second coating layer 12 can be a cross-linked fluoroelastomer.

[0031] The inventors of the present invention have conducted extensive research into a multi-core cable including a plurality of electric wires having heat and chemical resistance, and as a result have found that a multi-core cable having heat and chemical resistance can be obtained by forming a first coating layer covering the conductor of the coated electric wire from a cross-linked fluoroelastomer or a cross-linked fluororesin and a second coating layer covering the plurality of coated electric wires from a cross-linked fluoroelastomer, thereby completing the present invention.

[0032] Hereinafter, each component of the multi-core cable of this embodiment will be described. (1) Insulated wire The coated electric wire 11 can have a conductor 111 and a first coating layer 112 that covers the conductor 111 . (conductor) The conductor 111 can be made of a single metal wire or multiple metal wires. When the conductor 111 has multiple metal wires, the multiple metal wires can be twisted together. In other words, when the conductor 111 has multiple metal wires, the conductor 111 can be a twisted wire of multiple metal wires.

[0033] The conductor 111 may have a circular outer shape in a cross section perpendicular to the longitudinal direction. A circular conductor may be formed by compressing the conductor radially. The conductor 111 may also have surface irregularities that conform to the outer shapes of the multiple metal wires.

[0034] The material of the conductor 111 is not particularly limited, but may be one or more commonly used conductor materials selected from the group consisting of copper, soft copper, silver-plated soft copper, nickel-plated soft copper, tin-plated soft copper, and the like. (1st coating layer) The material of the first covering layer 112 is preferably a cross-linked fluoroelastomer or a cross-linked fluororesin. The fluororesin used for the first covering layer 112 is preferably, for example, ETFE, which is a copolymer of ethylene and tetrafluoroethylene. The fluoroelastomer will be described collectively in the second covering layer.

[0035] The first covering layer 112 can be a cross-linked fluoroelastomer, which is a cross-linked fluoroelastomer, or a cross-linked fluororesin, which is a cross-linked fluororesin, by coating the outer surface of the conductor 111 with a fluoroelastomer or a fluororesin and then performing a cross-linking treatment with ionizing radiation such as gamma rays or electron beams. The second covering layer 12 described below can also be cross-linked with ionizing radiation. When performing the cross-linking treatment on the second covering layer 12, the ionizing radiation penetrates into the inside of the multi-core cable 10, so that the first covering layer 112 is also cross-linked.

[0036] Therefore, the first coating layer 112 is cross-linked a first time when the first coating layer 112 is cross-linked, and a second time when the second coating layer is cross-linked. Therefore, the first coating layer 112 can be a cross-linked fluoroelastomer or cross-linked fluororesin that has been cross-linked twice.

[0037] The multi-core cable 10 of the present embodiment may have a plurality of covered electric wires 11. The number of covered electric wires 11 included in the multi-core cable 10 of the present embodiment is not particularly limited, and any number of covered electric wires 11 may be included depending on the device to be connected, etc. The multi-core cable 10 of the present embodiment may have, for example, two or more covered electric wires 11.

[0038] The multiple covered electric wires 11 of the multi-core cable 10 of the present embodiment may be twisted together. By twisting the multiple covered electric wires 11 together and selecting the twist pitch, the adhesive strength (adhesion force) between the multiple covered electric wires 11 and the second covering layer 12 can be adjusted.

[0039] When multiple coated electric wires 11 are twisted together, the twist pitch is not particularly limited, but is preferably, for example, 5 mm or more and 60 mm or less, more preferably 10 mm or more and 50 mm or less, and even more preferably 10 mm or more and 40 mm or less.

[0040] By setting the twist pitch of the multiple covered electric wires 11 to 60 mm or less, the adhesive strength of the second covering layer 12 to the multiple covered electric wires 11 can be sufficiently increased, and the chemical resistance can be particularly increased. In addition, the noise resistance can be increased.

[0041] Moreover, by setting the twist pitch of the multiple covered electric wires 11 to 5 mm or more, the second covering layer 12 can be easily peeled off from the multiple covered electric wires 11, and the workability when connecting a connector or the like to an end of the multi-core cable can be improved. Also, the productivity when twisting the multiple covered electric wires 11 can be improved.

[0042] The twist pitch can be measured by the method described in JIS C 3002 (1992). (2) Second coating layer The multi-core cable 10 of the present embodiment can have a second covering layer 12 that covers the multiple covered electric wires 11. As shown in Fig. 1, the second covering layer 12 can cover the multiple covered electric wires 11 collectively, i.e., collectively.

[0043] The material of the second coating layer 12 is preferably a cross-linked fluoroelastomer.

[0044] As the fluoroelastomer, it is preferable to use any one of materials selected from, for example, tetrafluoroethylene / propylene copolymer (hereinafter referred to as "TFE-P copolymer"), vinylidene fluoride rubber (hereinafter referred to as "FKM"), a mixture of TFE-P copolymer and ethylene / tetrafluoroethylene copolymer (hereinafter referred to as "E-TFE copolymer"), and a mixture of FKM and polyvinylidene fluoride (PVDF). When a fluoroelastomer is used in the first covering layer 112, it is preferable to use any one of the fluoroelastomers selected from the above materials.

[0045] The second coating layer 12 can be formed by coating the outer surfaces of the multiple coated electric wires 11 with a fluoroelastomer, and then subjecting the outer surfaces to a crosslinking treatment using ionizing radiation such as gamma rays or electron beams to form a crosslinked fluoroelastomer.

[0046] The thickness of the second coating layer 12 is not particularly limited, but is preferably, for example, 0.1 mm or more and 0.6 mm or less, and more preferably 0.2 mm or more and 0.5 mm or less.

[0047] By making the thickness of the second covering layer 12 0.1 mm or more, the covered electric wire 11 can be sufficiently protected and durability can be increased. By making the thickness 0.6 mm or less, the multi-core cable can be easily bent and lightened. In addition, the cord diameter of the multi-core cable can be reduced, so the space required for installing the multi-core cable can be reduced.

[0048] The thickness T of the second coating layer 12 refers to the thickness at the location where the thickness of the second coating layer 12 is the thinnest. Therefore, the distance between the circumscribing circle O of the multiple coated electric wires 11 and the outer surface of the second coating layer 12 can be the thickness T of the second coating layer 12. When a lubricant 13, which will be described later, is included, the thickness T of the second coating layer 12 can be the distance between the circumscribing circle O of the multiple coated electric wires 11 on which the lubricant 13 is disposed and the outer surface of the second coating layer 12, as shown in FIG. 1.

[0049] As described above, the multi-core cable of this embodiment has two resin layers covering the conductor 111: the first covering layer 112 included in the covered electric wire 11 and the second covering layer 12 covering the multiple covered electric wires 11.

[0050] Furthermore, by using cross-linked materials for both first covering layer 112 and second covering layer 12, the decomposition temperature becomes high, and therefore a multi-core cable with excellent heat resistance can be obtained.

[0051] In addition, since the cross-linked fluororesin and the cross-linked fluoroelastomer are both fluorine-based resins or elastomers, they also have excellent chemical resistance. Therefore, by making a multi-core cable having the first covering layer 112 and the second covering layer 12, it is possible to make the multi-core cable have excellent chemical resistance.

[0052] The first coating layer can be made of a crosslinked fluoroelastomer or a crosslinked fluororesin, and when the first coating layer is made of a crosslinked fluororesin, the layer has particularly high hardness. Therefore, when the first coating layer is made of a crosslinked fluororesin, the internal conductor can be particularly prevented from being crushed and broken even when an external force is applied to the multi-core cable.

[0053] Since the crosslinked fluoroelastomer is softer than the crosslinked fluororesin, the use of the crosslinked fluoroelastomer for the second covering layer 12 that is the outer periphery of the multicore cable can improve the handleability of the multicore cable.

[0054] Furthermore, when different materials are used, for example, the first covering layer 112 is made of a cross-linked fluororesin and the second covering layer 12 is made of a cross-linked fluoroelastomer, it is possible to particularly prevent the first covering layer 112 and the second covering layer 12 from fusing together when, for example, heat is applied to form the second covering layer 12. This improves the peelability of the second covering layer 12 from the covered electric wire 11, and improves the workability when connecting a connector or the like to the end of the multi-core cable.

[0055] The multi-core cable of this embodiment may further include any optional components in addition to the components described above.

[0056] The multi-core cable of the present embodiment may further include a lubricant. Specifically, the multi-core cable of the present embodiment may have a configuration in which the lubricant 13 is disposed between the first covering layer 112 and the second covering layer 12, that is, on the surfaces of the multiple covered electric wires 11.

[0057] By disposing the lubricant 13 between the first covering layer 112 and the second covering layer 12, it is possible to adjust the adhesion of the second covering layer 12 to the first covering layer 112. By disposing the lubricant 13, it is possible to improve the peelability of the second covering layer 12 from the covered electric wire 11, and to improve the workability when connecting a connector or the like to the end of the multi-core cable.

[0058] The material of the lubricant 13 is not particularly limited, but for example, talc or the like can be used.

[0059] In the multi-core cable of this embodiment, the adhesion strength of the second coating layer to the first coating layer per 35 mm length is preferably 20 N or more and 150 N or less, more preferably 25 N or more and 125 N or less, and even more preferably 25 N or more and 100 N or less.

[0060] By setting the adhesion strength of the second coating layer to the first coating layer per 35 mm length to 150 N or less, the second coating layer 12 can be easily peeled from the multiple coated electric wires 11, thereby improving the workability when connecting a connector or the like to the end of the multi-core cable.

[0061] By setting the adhesion of the second coating layer to the first coating layer per 35 mm length to 20 N or more, the adhesion of the second coating layer 12 to the multiple coated electric wires 11 can be sufficiently increased, and chemical resistance can be particularly improved.

[0062] The adhesion of the second coating layer to the first coating layer per 35 mm length can be measured using, for example, an adhesion measuring tool 31 shown in FIG. 3 that has through holes through which only the multiple coated electric wires 11 can pass.

[0063] First, the second covering layer 12 of the multi-core cable 10 is removed except for a portion thereof to expose the multiple covered electric wires 11. At this time, as shown in Fig. 3, the second covering layer 12 is left so that the length L of the second covering layer 12 along the longitudinal direction of the multi-core cable 10 is 35 mm.

[0064] The exposed covered electric wires 11 are inserted into the through holes of the adhesion measuring jig 31. In this way, the multi-core cable 10 is set in the adhesion measuring jig 31 as shown in FIG.

[0065] Next, with the adhesion measuring jig 31 fixed, the multi-core cable 10 is pulled along the arrow A in Fig. 3. Then, the magnitude of the force applied when the second coating layer 12 peels off from the multiple coated electric wires 11 and the multiple coated electric wires 11 pass through the through holes of the adhesion measuring jig 31 and move below the adhesion measuring jig 31 is measured. The magnitude of the measured force can be regarded as the adhesion force of the second coating layer to the first coating layer per 35 mm length. 2. Manufacturing method of multi-core cable The method for producing the multi-core cable of the present embodiment is not particularly limited, but for example, the multi-core cable can be produced by the following procedure. Since the multi-core cable production method of the present embodiment can produce the multi-core cable described above, some of the matters already described will not be described.

[0066] A first covering step of covering the surface of the conductor 111 with a fluorine elastomer or a fluorine resin. A first cross-linking step in which the fluorine elastomer or fluorine resin disposed on the surface of the conductor 111 is cross-linked by ionizing radiation. A second covering step of covering the surfaces of the multiple covered electric wires obtained after the first crosslinking step with a fluoroelastomer. A second crosslinking process in which the fluoroelastomer disposed on the surfaces of the multiple coated electric wires is crosslinked by ionizing radiation.

[0067] Each step will be described below. (First coating process) In the first covering step, for example, the surface of the conductor 111 can be covered with a fluoroelastomer or a fluororesin. The method for covering the surface of the conductor 111 with a fluoroelastomer or a fluororesin is not particularly limited, but for example, extrusion molding can be used. Since the fluoroelastomers and fluororesins that can be suitably used have already been described, a description thereof will be omitted here.

[0068] Materials suitable for use in the conductor 111 to be subjected to the first covering step have already been described, and so a detailed description thereof will be omitted here. When the conductor 111 has a plurality of metal wires, the plurality of metal wires may be twisted together in advance. In addition, the conductor may be circularly compressed in the radial direction as necessary. (1st crosslinking step) In the first crosslinking step, ionizing radiation can be used to crosslink the fluoroelastomer or fluororesin that covers the conductor 111. As the ionizing radiation, for example, gamma rays or electron beams can be used, but it is preferable to use electron beams from the viewpoint of ease of handling. (Second coating process) In the second covering step, the surfaces of the multiple covered electric wires 11 can be covered with a fluoroelastomer. The method for covering the surfaces of the multiple covered electric wires 11 with a fluoroelastomer is not particularly limited, but for example, extrusion molding can be used. Since the fluoroelastomer that can be suitably used has already been described, the description thereof will be omitted here.

[0069] The plurality of covered electric wires 11 to be subjected to the second covering step may be twisted together in advance. Therefore, the method for producing a multi-core cable according to the present embodiment may include a twisting step of twisting together the plurality of covered electric wires 11 after the first cross-linking step and before the second covering step.

[0070] As described above, the multi-core cable 10 of this embodiment can also have the lubricant 13 between the first covering layer 112 and the second covering layer 12, i.e., on the surfaces of the multiple covered electric wires 11. For this reason, the manufacturing method for the multi-core cable of this embodiment can have a lubricant applying step of applying a lubricant on the surfaces of the multiple covered electric wires 11 after the first cross-linking step and before the second covering step. (Second crosslinking step) In the second crosslinking step, ionizing radiation can be used to crosslink the fluoroelastomer that covers the multiple covered electric wires 11. As the ionizing radiation, for example, gamma rays or electron beams can be used, but it is preferable to use electron beams from the viewpoint of handling.

[0071] According to the method for producing a multi-core cable of the present embodiment described above, it is possible to produce the multi-core cable described above, which has excellent heat resistance and chemical resistance. 3. Harness As shown in FIG. 2, a harness 20 of this embodiment can include the multi-core cable 10 described above, and connectors 21A, 21B disposed at both ends in the longitudinal direction of the multi-core cable.

[0072] The harness 20 of the present embodiment uses the multi-core cable 10 described above, and therefore has excellent heat resistance and chemical resistance. In addition, since the multi-core cable 10 has a plurality of covered electric wires, a plurality of terminals can be connected simultaneously, and wiring can be easily performed.

[0073] The length L of the multi-core cable 10 that connects the connectors 21A and 21B of the harness 20 of this embodiment 10 is not particularly limited.

[0074] Although the embodiments have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the claims. EXAMPLES

[0075] The present invention will be described below with reference to specific examples, but is not limited to these examples. (Evaluation method) First, the method for evaluating the multi-core cables produced in the following experimental examples will be described. (1) Adhesion of the second coating layer The measurement was performed using an adhesion measuring jig 31 shown in FIG. 3, which had through holes through which only the multiple covered electric wires 11 could pass.

[0076] First, the second covering layer 12 of the multi-core cable 10 was removed except for a part thereof to expose the multiple covered electric wires 11. At this time, the second covering layer 12 was left so that the length L of the second covering layer 12 along the longitudinal direction of the multi-core cable 10 was 35 mm, as shown in FIG.

[0077] Then, the exposed coated electric wires 11 were inserted into the through holes of the adhesion measuring jig 31. In this way, the multi-core cable 10 was set in the adhesion measuring jig 31 as shown in FIG.

[0078] Next, with the adhesion measuring jig 31 fixed, the multi-core cable 10 was pulled at a speed of 200 mm / min along the arrow A in Fig. 3. Then, the magnitude of the force applied when the second coating layer 12 peeled off from the multiple coated electric wires 11 and the multiple coated electric wires 11 passed through the through holes of the adhesion measuring jig 31 and moved downward of the adhesion measuring jig 31 was measured. The magnitude of the measured force can be regarded as the adhesion of the second coating layer to the first coating layer per 35 mm in length, and is referred to as the second coating layer adhesion in Table 1 etc. (2) Chemical resistance The evaluation was conducted based on JASO D 618:2014, Section 6.11.2. However, the temperature of the aging bath when evaluating the multi-core cables of each experimental example was the same as the temperature of heat resistance determined in the heat resistance test below. If the cable passed all chemicals, it was rated as A for excellent chemical resistance, and if it did not pass some or all chemicals, it was rated as B for poor chemical resistance. (3) Heat resistance The evaluation was conducted based on JASO D 609:2012, and the heat resistance was determined based on 10,000 hours of continuous use. (4) Core collapse In any cross section perpendicular to the longitudinal direction of the multi-core cable produced in each experimental example, if the thickness of the thinnest part of the first coating layer of the two insulated wires was 80% or more of the predetermined standard thickness, core crushing was suppressed and rated as A, and if the thickness was less than 80%, core crushing was observed and rated as B. (5) Processability For the multi-core cables produced in each experimental example, when the second coating layer was peeled off by 50 mm along the longitudinal direction, if it was not visually confirmed that the second coating layer remained on the surface of the first coating layer, the cable was evaluated as having excellent processability and given an A. If it was visually confirmed that the second coating layer remained on the surface of the first coating layer, the cable was evaluated as having poor processability and given a B.

[0079] The multi-core cables in each of the experimental examples will be described below. Experimental Examples 1 to 5 are working examples, and Experimental Examples 6 to 8 are comparative examples. (Experimental Example 1) By twisting together 19 soft copper wires with a diameter of 0.19 mm, the cross-sectional area is 0.5 mm 2 A conductor 111 was prepared.

[0080] A fluoroelastomer was disposed around the outer periphery of the conductor 111 by extrusion molding, thereby covering the surface of the conductor 111 with the fluoroelastomer (first covering step).

[0081] The fluoroelastomer used was a mixture of TFE-P copolymer and E-TFE copolymer. In the first coating step, coating was performed so that the outer diameter of the first coating layer was 1.55 mm.

[0082] Next, the fluorine elastomer disposed on the surface of the conductor 111 was crosslinked by ionizing radiation (first crosslinking step). An electron beam was used as the ionizing radiation.

[0083] The two covered electric wires 11 obtained in the first cross-linking step were twisted together at a twist pitch of 5 mm (twisting step).

[0084] The fluoroelastomer was disposed around the outer periphery of the twisted insulated electric wires by extrusion molding, so that the surfaces of the insulated electric wires 11 were covered with the fluoroelastomer (second covering step).

[0085] The fluoroelastomer used was a mixture of TFE-P copolymer and E-TFE copolymer. In the second coating step, coating was performed so that the outer diameter of the second coating layer was 3.9 mm.

[0086] Next, the fluoroelastomer disposed on the surfaces of the multiple coated electric wires 11 was crosslinked by ionizing radiation (second crosslinking step). An electron beam was used as the ionizing radiation. When the second crosslinking step was performed, the electron beam also reached the first coating layer, so that the first coating layer was also crosslinked again in the second crosslinking step.

[0087] The resulting multi-core cable was subjected to the evaluations described above, and the evaluation results are shown in Table 1. (Experimental Example 2) A multi-core cable was produced and evaluated in the same manner as in Experimental Example 1, except that the twist pitch in the twisting process was set to 10 mm. The evaluation results are shown in Table 1. (Experimental Example 3) In the first covering step, a fluororesin was used as the resin to be placed around the outer periphery of the conductor 111, and the first covering layer was covered so that the outer diameter of the first covering layer was 1.45 mm. ETFE, a copolymer of ethylene and tetrafluoroethylene, was used as the fluororesin.

[0088] In the second covering step, the second covering layer was formed so that the outer diameter of the second covering layer was 3.8 mm.

[0089] Except for the above points, a multi-core cable was produced and evaluated in the same manner as in Experimental Example 2. The evaluation results are shown in Table 1. (Experimental Example 4, Experimental Example 5) Multi-core cables were produced and evaluated in the same manner as in Experimental Example 3, except that in the twisting process, the twist pitch was set to the value shown in Table 1. The evaluation results are shown in Table 1. (Experimental Example 6) In the first and second covering steps, PVC (polyvinyl chloride) was used as the resin placed on the conductor or on the outer periphery of the multiple covered electric wires, and the second crosslinking step was not performed. In the following explanation and in Table 1, etc., polyvinyl chloride will be simply referred to as PVC.

[0090] In the first covering step, the first covering layer was formed so as to have an outer diameter of 1.6 mm, and in the second covering step, the second covering layer was formed so as to have an outer diameter of 4 mm.

[0091] Except for the above, a multi-core cable was produced and evaluated in the same manner as in Experimental Example 1. The evaluation results are shown in Table 1. (Experimental Example 7) In the first covering process, PE (polyethylene) was used as the resin placed around the conductor, and in the second covering process, PVC was used as the resin placed around the multiple covered wires. The second cross-linking process was not performed. In the following explanation and Table 1, polyethylene will be simply referred to as PE.

[0092] In the first covering step, the first covering layer was formed so as to have an outer diameter of 1.6 mm, and in the second covering step, the second covering layer was formed so as to have an outer diameter of 4 mm.

[0093] Except for the above, a multi-core cable was produced and evaluated in the same manner as in Experimental Example 1. The evaluation results are shown in Table 1. (Experimental Example 8) PE was used as the resin to be placed around the conductor or the outer periphery of multiple coated electric wires in the first and second coating processes.

[0094] In the first covering step, the first covering layer was formed so as to have an outer diameter of 1.6 mm, and in the second covering step, the second covering layer was formed so as to have an outer diameter of 4 mm.

[0095] Except for the above, a multi-core cable was produced and evaluated in the same manner as in Experimental Example 1. The evaluation results are shown in Table 1.

[0096] [Table 1] According to the results shown in Table 1, the multi-core cables of Experimental Examples 1 to 5 were evaluated as having an A for chemical resistance and an A for heat resistance of 200°C, confirming that they are multi-core cables with excellent heat resistance and chemical resistance. On the other hand, the multi-core cables of Experimental Examples 6 to 8 were evaluated as having a B for chemical resistance and an A for heat resistance of 125°C or less or 105°C or less, confirming that they are inferior in both chemical resistance and heat resistance compared to the multi-core cables of Experimental Examples 1 to 5.

[0097] In the multi-core cables of Experimental Examples 1 to 5, a cross-linked fluororesin or a cross-linked fluoroelastomer was used as the material for the first coating layer, and a cross-linked fluoroelastomer was used as the material for the second coating layer. It is believed that cross-linking both materials for coating the conductor in this way increases the thermal decomposition temperature and improves heat resistance. It is also believed that using a fluororesin or elastomer as the material for the first and second coating layers improves chemical resistance. [Explanation of symbols]

[0098] 10 Multi-core cable 11 Covered wire 111 Conductor 112 1st coating layer 12 Second coating layer 13 Lubricants 20 Harness 21A, 21B Connectors 31 Adhesion strength measuring tool O Circumscribed circle T Thickness A Arrow L Length L 10 length

Claims

1. A plurality of coated electric wires and a second coating layer that covers an outer periphery of the plurality of coated electric wires, The coated electric wire includes a conductor and a first coating layer that covers the conductor, The first coating layer is a cross-linked fluororesin, which is a copolymer of ethylene and tetrafluoroethylene; the second coating layer is a crosslinked fluoroelastomer that is softer than the crosslinked fluororesin, A lubricant is disposed between the first coating layer and the second coating layer, A multi-core cable in which the adhesion strength of the second coating layer to the first coating layer per 35 mm length is 25 N or more and 150 N or less.

2. 2. The multi-core cable according to claim 1, wherein the crosslinked fluoroelastomer is any material selected from the group consisting of tetrafluoroethylene / propylene copolymer, vinylidene fluoride rubber, a mixture of tetrafluoroethylene / propylene copolymer and ethylene / tetrafluoroethylene copolymer, and a mixture of vinylidene fluoride rubber and polyvinylidene fluoride.

3. 3. The multi-core cable according to claim 1, wherein the plurality of covered electric wires are twisted together at a twist pitch of 5 mm or more and 60 mm or less.

4. 4. The multi-core cable according to claim 1, wherein the second coating layer has a thickness of 0.1 mm or more and 0.6 mm or less.

5. A multi-core cable according to any one of claims 1 to 4; and connectors arranged at both longitudinal ends of the multi-core cable.

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