Multi-core cable

Abstract

A multi-core cable (1) is provided, which is easy to arrange in a housing and can also detect temperature rise in the cable. A multi-core cable (1) comprises a heat detection wire (2) comprising a twisted pair (22) formed by twisting a pair of heat detection wires (21) having a first conductor (211) and a first insulator (212) covering the first conductor (211), a plurality of wires (3) having a second conductor (31) and a second insulator (32) covering the second conductor (31), and a sheath (4) covering the heat detection wire (2) and the plurality of wires (3), wherein the melting point of the first insulator (212) is lower than the melting point of the second insulator (32).

Description

Technical Field

[0001] The invention relates to a multi-core cable. Background Art

[0002] In the past, fire detection wires were used to detect fires (see, for example, Patent Document 1). The fire detection wires are composed of a twisted pair of fire detection wires having a conductor made of steel wire and a low-melting-point insulator covering the conductor, and the twisted pair is covered with a sheath.

[0003] Conventionally, the fire detection line is arranged along the cable to be detected as a temperature rise. For example, in a multi-core cable used for contactless power supply, the fire detection line is provided between the multi-core cable and a housing accommodating the multi-core cable.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 58-86695 Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, in the above configuration structure, the cables and the fire detection line must be arranged separately, so there is a problem that the arrangement work consumes labor. For example, in a multi-core cable used for contactless power supply, after the multi-core cable is stored in the housing, the fire detection line must be arranged in the housing along the multi-core cable, and the arrangement work in the housing consumes a lot of labor.

[0009] In addition, in a multi-core cable laid in a housing, for example, when used for contactless power supply, a large current flows through the wires arranged in the multi-core cable. It is intended to prevent the following problems: when a large current flows through the multi-core cable, an overcurrent is generated, thereby causing the temperature in the cable to rise, resulting in a fire.

[0010] Therefore, an object of the present invention is to provide a multi-core cable that is easy to arrange in a housing and can also detect a temperature rise in the cable.

[0011] Methods for solving problems

[0012] For the purpose of solving the above-mentioned problems, the present invention provides a multi-core cable, which comprises a heat detection wire including a twisted pair of wires, a plurality of wires having a second conductor and a second insulator covering the periphery of the aforementioned second conductor, and a sheath covering the aforementioned heat detection wire and the aforementioned plurality of wires together; the aforementioned twisted pair of wires is formed by twisting a pair of heat detection wires having a first conductor and a first insulator covering the periphery of the aforementioned first conductor; and the melting point of the aforementioned first insulator is lower than the melting point of the aforementioned second insulator.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to provide a multi-core cable that is easy to arrange in a housing and that is also capable of detecting a temperature rise in the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 In the figure, (a) is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the multi-core cable according to one embodiment of the present invention, and (b) is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the cable of a heat detection line.

[0016] Figure 2 This is a perspective view showing the appearance of a multi-core cable.

[0017] Figure 3 This is a cross-sectional view when a multi-core cable is accommodated in the groove of the housing.

[0018] Explanation of symbols

[0019] 1: multi-core cable, 2: heat detection wire, 21: heat detection wire, 211: first conductor, 212: first insulator, 212a: inner insulator, 212b: outer insulator, 22: twisted pair, 23: winding tape, 24: sleeve, 3: wire, 31: second conductor, 32: second insulator, 4: sheath, 41: hollow part, 5: air layer, 6: assembly. DETAILED DESCRIPTION

[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0021] Figure 1 (a) is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of the multi-core cable according to the present embodiment, Figure 1 (b) is a cross-sectional view showing a cross section of the heat detection line perpendicular to the length direction of the cable. Figure 2 This is a perspective view showing the appearance of a multi-core cable. Figure 3 This is a cross-sectional view when a multi-core cable is accommodated in the groove of the housing.

[0022] like Figures 1 to 3 As shown, the multi-core cable 1 includes a heat detection wire 2 , a plurality of electric wires 3 , and a sheath 4 that covers the heat detection wire 2 and the plurality of electric wires 3 together.

[0023] The multi-core cable 1 is used to supply power in a non-contact manner and is stored in a groove 11 of a housing 10. In this example, the housing 10 has a pair of side walls 12 arranged in parallel and a bottom wall 13 connecting the ends of the side walls 12 to each other and perpendicular to the side walls 12, and as a whole, it forms a "コ" shape rotated 90 degrees in the clockwise direction in cross-sectional observation. The space surrounded by the pair of side walls 12 and the bottom wall 13 and opening on the opposite side of the bottom wall 13 and having a rectangular shape in cross-sectional observation is the groove 11.

[0024] (Heat detection line 2)

[0025] The heat detection wire 2 includes a twisted pair 22 formed by twisting a pair of heat detection electric wires 21 , a wrapping tape 23 spirally wrapped around the twisted pair 22 , and a sleeve 24 covering the wrapping tape 23 .

[0026] The heat detection wire 21 constituting the twisted pair 22 has a first conductor 211 made of a steel wire, a copper wire, or the like, and a first insulator 212 covering the first conductor 211. As the first conductor 211, a conductor made of a steel wire having a higher rigidity than the second conductor 31 described later and a greater force than the second conductor 31 to return to a straight line when bent can be used. As the steel wire used as the first conductor 211, a steel wire made of stainless steel (SUS), a piano wire made of carbon steel, or a steel wire made of other alloys can be used. In the present embodiment, a single-wire steel wire made of stainless steel with a diameter of 0.9 mm is used as the first conductor 211.

[0027] In order to melt when the temperature in the cable rises, an insulating resin with a relatively low melting point is used as the first insulator 212. More specifically, the melting point of the first insulator 212 is lower than the melting point (for example, 105°C or more) of the second insulator 32 (described later) of the electric wire 3, so that the first insulator 212 melts before the second insulator 32 of the electric wire 3 melts due to the heat when the temperature in the cable rises due to an overcurrent or the like (in other words, before the electric wire 3 loses its function due to the heat when the temperature rises, the first conductor 211 short-circuits, thereby detecting the temperature rise in the cable due to the occurrence of an overcurrent or the like). In the present embodiment, the melting point of the first insulator 212 is set to about 90°C.

[0028] In the heat detection line 2, if the temperature in the cable (the temperature around the electric wire 3) rises to a temperature above the melting point of the first insulator 212 (about 90°C in this embodiment) and below the melting point of the second insulator 32, and the first insulator 212 melts due to the heat at this time, the two first conductors 211 constituting the twisted pair 22 come into contact with each other, and an electrical short circuit occurs. By detecting the short circuit of the two first conductors 211, it is possible to detect the temperature rise in the multi-core cable 1 caused by an overcurrent or the like. In particular, when the first conductor 211 is made of steel wire, due to its high rigidity, the force to return to a straight shape when bent is large (for example, larger than the second conductor 31), so it is easier to apply a force that always brings the two first conductors 211 constituting the twisted pair 22 closer to each other than the first conductor 211 made of a material other than steel wire. Therefore, when the first insulator 212 melts, the two first conductors 211 constituting the twisted pair 22 are easy to come into contact with each other, and an electrical short circuit is easy to occur.

[0029] It should be noted that before the two first conductors 211 are short-circuited due to the temperature rise around the heat detection line 2, the first insulator 212 softens, the distance between the two first conductors 211 becomes closer, and the resistance value and capacitance between the two first conductors 211 change. Therefore, by measuring the resistance value and capacitance between the two first conductors 211, the temperature rise around the heat detection line 2 can be detected before the two first conductors 211 are short-circuited.

[0030] The first insulator 212 may be a multilayer structure in which a plurality of layers composed of an insulating resin composition are stacked. In the present embodiment, the first insulator 212 is a two-layer structure composed of an inner insulator 212a covering the periphery of the first conductor 211 and an outer insulator 212b covering the periphery of the inner insulator 212a. However, the first insulator 212 is not limited thereto, and may be a single-layer structure or a multilayer structure of more than three layers. The insulating resin composition is composed of a substance containing a resin described later. In addition, the resin compositions constituting each layer may be different from each other.

[0031] As described above, the melting points of the inner insulator 212a (the layer closest to the first conductor 211) and the outer insulator 212b are lower than the melting point of the second insulator 32 of the electric wire 3. In this embodiment, the melting point of the inner insulator 212a and the melting point of the outer insulator 212b are set to be equal to about 90°C. In this embodiment, the inner insulator 212a can be composed of a resin composition having a polyethylene resin or a resin containing EVA (ethylene-vinyl acetate copolymer) as a main component (base resin). In addition, in this embodiment, the outer insulator 212b can be composed of a resin composition having a resin containing PVC (polyvinyl chloride) as a main component. By constituting the inner insulator 212a and the outer insulator 212b with the above-mentioned resin composition, it is easy to show the effect of detecting the temperature rise in the above-mentioned multi-core cable 1. In addition, the melting point of the inner insulator 212a can be higher than the melting point of the outer insulator 212b. In this case, the temperature rise in the multi-core cable 1 can also be detected in stages.

[0032] In addition, the outer insulator 212b may be formed of a resin composition containing a granular substance having a higher melting point than each insulating resin constituting the first insulator 212. When the first insulator 212 is a multilayer structure having three or more layers, the granular substance may be contained in at least one layer other than the layer closest to the first conductor 211 (here, the inner insulator 212a).

[0033] The inventors of the present invention have found that when the temperature around the heat detection line 2 rises, there is a situation where a thin portion of the melted first insulator 212 remains, making it difficult for the two conductors 2 to short-circuit. When the temperature around the heat detection line 2 rises, the outer insulator 212b of the first insulator 212 contains a granular material with a high melting point. When the temperature around the heat detection line 2 rises, the granular material is pressed in by the force that brings the first conductors 211 closer to each other, causing the remaining thin first insulator 212 to be damaged, making it easy for the first conductors 211 to short-circuit. If the granular material is insulating, there is a possibility that the granular material is embedded between the first conductors 211 without causing a short circuit. Therefore, as the granular material, it is preferable to use a conductive material. As the granular material, for example, carbon particles can be used.

[0034] As the wrapping tape 23 wound around the twisted wire pair 22, for example, a resin tape such as a polyester tape can be used. The wrapping tape 23 is spirally wound around the twisted wire pair 22 so that parts of the wrapping tape 23 in the width direction overlap.

[0035] The sleeve 24 functions as a protective layer for protecting the twisted pair 22. The sleeve 24 preferably has a higher melting point than the first insulator 212 so that the sleeve 24 does not melt before the first insulator 212 melts. The sleeve 24 is made of an insulating resin and is formed by non-full extrusion molding (so-called tube extrusion molding).

[0036] In addition, in the present embodiment, the sleeve 24 is made of an elastic body. In the present embodiment, the heat detection line 2 is arranged at the cable center of the multi-core cable 1. When the multi-core cable 1 is housed in the groove 11, the multi-core cable 1 is housed in the groove 11 by pressing the multi-core cable 1 into the groove 11 of the housing 10. Moreover, when the multi-core cable 1 is pressed, the wires 3 in the multi-core cable 1 are pressed on the heat detection line 2 arranged at the center of the cable. At this time, the sheath 24 of the heat detection line 2 is elastically deformed due to the force when the wires 3 are pressed, and the wires 3 in the sheath 4 can move relative to the circumferential direction and radial direction of the heat detection line 2 (in the cross section of the multi-core cable 1 perpendicular to the cable length direction, in the direction along the outer circumference of the heat detection line 2, in the direction along the outer diameter of the heat detection line 2). Therefore, the outer shape of the multi-core cable 1 can be deformed according to the shape and size of the groove 11. As a result, the multi-core cable 1 can easily enter the groove 11 of the housing 10 even if its outer diameter is thick.

[0037] In this way, the sheath 24 of the heat detection line 2 performs the function of elastically deforming to improve the operability when the multi-core cable 1 is stored in the groove 11. In addition, after the multi-core cable 1 is stored in the groove 11, the shape of the sheath 24 is restored due to the relaxation of the pressing force from the electric wire 3. Due to the restoring force of the sheath 24 at this time, the electric wire 3 in the sheath 4 moves to the original position (the position before being stored in the groove 11). As a result, the multi-core cable 1 stored in the groove 11 returns to its shape before deformation and remains in the groove 11. In this way, the sheath 24 of the heat detection line 2 also performs the function of pressing the sheath 4 toward the housing 10 (the inner wall of the groove 11) via the electric wire 3 and keeping the multi-core cable 1 in the groove 11.

[0038] All the electric wires 3 are in direct contact with the outer peripheral surface of the sleeve 24. The sleeve 24 may be made of an elastic material whose shape changes due to an external force, for example, a resin composition made of PVC (polyvinyl chloride) resin or polyurethane resin.

[0039] (Wire 3)

[0040] The electric wires 3 each have a second conductor 31 (which is composed of a stranded conductor formed by twisting a plurality of bare wires together) and a second insulator 32 covering the second conductor 31. Electric wires of the same structure are used as the six electric wires 3. In the present embodiment, a tinned soft copper wire is used as the bare wire used in the second conductor 31. The outer diameter of the bare wire used in the second conductor 31 can be set to be greater than 0.15 mm and less than 0.32 mm. This is because if the outer diameter of the bare wire is less than 0.15 mm, it is easy to break, and if it exceeds 0.32 mm, there is a possibility that the bare wire will penetrate the second insulator 32 and come out when the thickness of the second insulator 32 is reduced.

[0041] As a method for twisting bare wires, a method called co-core twisting is known. However, in this method, when the second conductor 31 is formed, the bare wires are twisted in a stable state, and the shape of the second conductor 31 is difficult to change due to external forces when the multi-core cable 1 is stored in the groove 11. Therefore, as the second conductor 31, a conductor formed by concentrated twisting is used so that the shape of the second conductor 31 is easily changed by external forces when the multi-core cable 1 is stored in the groove 11. In this embodiment, 134 bare wires of 0.26 mm in diameter are concentratedly twisted to form a conductor with an outer diameter of about 3.5 mm (3.0 mm or more and 4.0 mm or less) and a conductor cross-sectional area of ​​7 mm 2 Above 8mm 2 The second conductor 31 is as follows.

[0042] In order to increase the cross-sectional area of ​​the conductor portion in the multi-core cable 1, it is preferred that the second insulator 32 of each wire 3 is as thin as possible. More specifically, the thickness of the second insulator 32 is preferably not less than 1 / 2 times and not more than 1 times the outer diameter of the bare wire used in the second conductor 31. When the thickness of the second insulator 32 is set to be less than 1 / 2 of the outer diameter of the bare wire, there is a possibility that the bare wire will pierce the second insulator 32 due to the external force when the multi-core cable 1 is accommodated in the groove 11; if it exceeds 1 times the outer diameter of the bare wire, the diameter of the wire 3 is large, which will lead to a larger diameter of the multi-core cable 1 as a whole. In this embodiment, the thickness of the second insulator 32 is set to about 0.2 mm (about 0.77 times the outer diameter of the bare wire).

[0043] In order to realize a larger capacity of power supply, the ratio of the outer diameter of the second conductor 31 to the outer diameter of the electric wire 3 can be set to 80% or more. In addition, if the second insulator 32 is too thin, the bare wire may penetrate the second insulator 32 as described above, so the ratio of the outer diameter of the second conductor 31 to the outer diameter of the electric wire 3 can be set to 95% or less. In addition, in order to realize a large capacity of power supply in a non-contact manner, the same current can be supplied to the second conductor 31 in each of the plurality of electric wires 3.

[0044] As the second insulator 32, in order to be thin-walled and to make the sleeve 24 of the heat detection line 2 elastically deformable, a material that is harder than the sleeve 24 and has a strong external pressure (difficult to deform due to external force when the multi-core cable 1 is stored in the groove 11) can be used, for example, ETFE (tetrafluoroethylene-ethylene copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride) and other fluororesins, polyimide, PEEK (polyetheretherketone) can be used. More preferably, as the second insulator 32, a fluororesin with good surface smoothness can be used, thereby, when an external force is applied, the wire 3 is easier to move in the sheath 4, and the insertion of the multi-core cable 1 into the groove 11 becomes easier.

[0045] The second insulator 32 is formed by non-full extrusion molding (so-called tube extrusion molding). As a result, the second insulator 32 is not tightly attached to the bare wire, and the bare wire can move relatively inside the second insulator 32. When an external force is applied, the cross-sectional shape of the wire 3 is easily deformed. Therefore, the insertion of the multi-core cable 1 into the slot 11 becomes easier.

[0046] (Collection 6)

[0047] A plurality of electric wires 3 are twisted in a spiral shape around the outer periphery of the heat detection wire 2. Hereinafter, a body in which a plurality of electric wires 3 are twisted around the heat detection wire 2 is referred to as an aggregate 6.

[0048] When the number of wires 3 used in the assembly 6 is 1 to 3, the multi-core cable 1 is less likely to be deformed by external force. Therefore, in the multi-core cable 1, the number of wires 3 used in the assembly 6 is set to 4 or more. In the present embodiment, the number of wires 3 used in the assembly 6 is set to 6 so that the outer diameter can be minimized and the total conductor resistance of all the wires 3 can be minimized.

[0049] In the assembly 6, the adjacent wires 3 in the circumferential direction of the cable are in contact with each other. In addition, all the wires 3 are in contact with the heat detection wire 2. The outer diameter of the heat detection wire 2 is appropriately adjusted to an outer diameter that can be in contact with all the wires 3 when the six wires 3 are arranged without gaps in the circumferential direction of the cable. In the present embodiment, the outer diameter of the heat detection wire 2 is set to be substantially the same as the outer diameter of the wire 3. More specifically, the outer diameters of the heat detection wire 2 and the wire 3 are set to approximately 4.1 mm. The outer diameter of the assembly 6 is set to approximately 11 mm to 13 mm.

[0050] In addition, in the present embodiment, each wire 3 constituting the assembly 6 is arranged in contact with the inner peripheral surface of the sheath 4, and no tape for winding is wound around the assembly 6. This is because, if the tape is wound, the tape will play a function of restricting the movement of the wire 3, and there is a possibility that the operability when inserting the multi-core cable 1 into the groove 11 will be reduced. It should be noted that in terms of manufacturing convenience, when the wire 3 must be kept in a twisted state, a thread (resin thread, cotton thread, etc.) can be spirally wound around the assembly 6.

[0051] In addition, in the present embodiment, no interlayer such as rayon is arranged between the heat detection wire 2 and the plurality of electric wires 3 and between the electric wires 3 and the sheath 4. This is to suppress the ignition of the interlayer due to temperature rise and to ensure a space (the air layer 5 described later) in which the electric wires 3 can move in the circumferential direction and the outer diameter direction of the heat detection wire 2 when an external force is applied.

[0052] (Sheath 4)

[0053] A sheath 4 is provided around the assembly 6. In the multi-core cable 1 according to the present embodiment, the sheath 4 is formed by non-full extrusion molding (so-called tube extrusion molding). The sheath 4 is formed into a hollow cylindrical shape having a hollow portion 41 along the length direction, and the heat detection line 2 and the electric wire 3 are arranged in the hollow portion 41. As a result, in the multi-core cable 1, each electric wire 3 is not in close contact with the sheath 4 and can move relatively in the sheath 4.

[0054] More specifically, the multi-core cable 1 has an air layer 5 (gap, void) in the valley portion formed around the contact portion (inside and outside in the radial direction) between the wires 3 as the interval between the adjacent wires 3 in the circumferential direction of the cable. By having the air layer 5, when an external force is applied, the wire 3 can move to the portion of the air layer 5, or the sheath 4 is deformed and enters the portion of the air layer 5, and the outer diameter of the multi-core cable 1 is easily changed. As a result, the operability when inserting the multi-core cable 1 into the groove 11 is improved.

[0055] In addition, as described above, in this embodiment, the tape for winding is omitted, and the wires 3 are directly in contact with the inner peripheral surface of the sheath 4. It is preferred that the sheath 4 is arranged in a manner that does not squeeze the wires 3 radially inward as much as possible, and it is preferred that the contact area between the wires 3 and the sheath 4 is as small as possible (point contact when observed in cross section).

[0056] The thickness of the sheath 4 is preferably 0.6 mm to 1.0 mm. This is because if the thickness of the sheath 4 is less than 0.6 mm, the resistance to external damage and insulation performance will decrease, and if the thickness of the sheath 4 is greater than 1.0 mm, the diameter of the multi-core cable 1 will increase.

[0057] Further, the sheath 4 is formed by non-full extrusion molding and the thickness of the sheath 4 is reduced to less than 1.0 mm. Figure 2 As shown, it is possible to produce projections and depressions on the outer surface of the sheath 4 in such a way that the sheath 4 protrudes at the position of the electric wire 3. As a result, when the multi-core cable 1 is inserted into the groove 11 of the housing 10, it is easy to press the multi-core cable 1 into the groove 11 of the housing 10. At the same time, the contact area between the multi-core cable 1 and the housing 10 (the inner surface of the groove 11) can be reduced, and the insertion of the multi-core cable 1 into the groove 11 becomes easier. In this embodiment, as the sheath 4, a sheath made of polyvinyl chloride with a thickness of 0.8 mm is used. The outer diameter of the entire multi-core cable 1 is set to about 13.2 mm (13 mm or more and 14 mm or less).

[0058] (Functions and Effects of Implementation Methods)

[0059] As described above, the multi-core cable 1 involved in this embodiment comprises: a heat detection line 2 including a twisted pair 22 formed by twisting a pair of heat detection wires 21 having a first conductor 211 composed of steel wires and a first insulator 212 covering the first conductor 211, a plurality of wires 3 having a second conductor 31 and a second insulator 32 covering the second conductor 31, and a sheath 4 covering the heat detection line 2 and the plurality of wires 3 together; the melting point of the first insulator 212 is lower than the melting point of the second insulator 32; and the plurality of wires 3 are spirally twisted around the heat detection line 2.

[0060] In the multi-core cable 1 used in contactless power supply, a plurality of electric wires 3 are arranged in the circumferential direction, so there is a dead spot in the center of the cable. By arranging the heat detection wire 2 in the center of the cable, the dead spot can be effectively utilized to realize the multi-core cable 1 having the heat detection wire 2 inside. As a result, there is no need to set up a heat detection wire separately from the multi-core cable 1, and the operability of the arrangement operation is improved.

[0061] In addition, by having the heat detection wire 2 inside the multi-core cable 1, when an overcurrent flows through the electric wire 3 for some reason and the temperature of the multi-core cable 1 rises, the heat detection wire 2 can be used to quickly (in real time) detect the temperature rise, and the occurrence of a fire caused by the overcurrent can be suppressed. In this embodiment, all the electric wires 3 are in contact with the heat detection wire 2, and the distance between each electric wire 3 and the heat detection wire 2 is equal. Therefore, when an overcurrent occurs in any electric wire 3, the heat detection wire 2 can be used to detect the heat caused by the overcurrent with high accuracy.

[0062] (Summary of implementation methods)

[0063] Next, the technical ideas understood from the above-described embodiments are described by citing the symbols in the embodiments. However, the symbols in the following description do not limit the constituent elements in the claims to the components specifically described in the embodiments.

[0064] [1] A multi-core cable (1) comprising: a heat detection wire (2) comprising a twisted pair (22) of a pair of heat detection wires (21) having a first conductor (211) and a first insulator (212) covering the first conductor (211) twisted together, a plurality of wires (3) having a second conductor (31) and a second insulator (32) covering the second conductor (31), and a sheath (4) covering the heat detection wire (2) and the plurality of wires (3); the melting point of the first insulator (212) is lower than the melting point of the second insulator (32).

[0065] [2] According to the multi-core cable (1) described in [1], the aforementioned heat detection wire (2) has a sleeve (24) covering the periphery of the aforementioned twisted pair (22), and the melting point of the aforementioned sleeve (24) is higher than the melting point of the aforementioned first insulator (212).

[0066] [3] According to the multi-core cable (1) described in [1] or [2], the first insulator (212) is composed of a multi-layer structure, and at least one layer other than the layer closest to the first conductor (211) is composed of a resin composition containing an insulating resin and a granular material having a higher melting point than the insulating resin.

[0067] [4] The multi-core cable (1) according to [3], wherein the granular material is conductive.

[0068] [5] The multi-core cable (1) according to any one of [1] to [4], wherein the plurality of electric wires (3) are twisted in a spiral shape around the heat detection wire (2).

[0069] [6] The multi-core cable (1) according to any one of [1] to [5], wherein the first conductor (211) is made of a steel wire.

[0070] The embodiments of the present invention have been described above, but the embodiments described above do not limit the inventions involved in the claims. In addition, it should be noted that all combinations of features described in the embodiments are not necessarily required to solve the problems of the invention.

[0071] In addition, the present invention can be implemented with appropriate modifications without departing from the scope of the purpose. For example, in the above embodiment, the sleeve 24 is formed by tube extrusion molding, but it is not limited to this, and the sleeve 24 can also be omitted. In this case, the wrapping tape 23 wrapped around the twisted pair 22 functions as a protective layer to protect the twisted pair 22.

[0072] Furthermore, when the first insulator 212 is a multilayer structure, the melting points of the layers can be different. Thus, when the temperature around the heat detection line 2 rises, the layers melt in sequence according to the temperature, and the distance between the first conductors 211 can be changed step by step according to the temperature. As a result, the temperature rise around the heat detection line 2 can be measured step by step by measuring the resistance value and capacitance between the two first conductors 211.

[0073] Furthermore, the above embodiment describes the case where six electric wires 3 are used, but four, five, or seven or more electric wires 3 may be used. When the number of electric wires 3 used is set to four or five, the outer diameter of the heat detection wire 2 can be made smaller than the outer diameter of the electric wire 3; when the number of electric wires used is set to seven or more, the outer diameter of the heat detection wire 2 can be made larger than the outer diameter of the electric wire 3.

[0074] Furthermore, in the above-mentioned embodiment, the case where the U-shaped housing 10 is used is described, but the shape of the housing 10 is not limited thereto, and for example, a portion thereof may be elliptical or polygonal.

Claims

1. A multi-core cable having: a heat detection wire including a twisted pair of wires formed by twisting a pair of heat detection wires having a first conductor and a first insulator covering the periphery of the first conductor, a plurality of wires having a second conductor and a second insulator covering the second conductor, and a sheath covering the heat detection wire and the plurality of electrical wires together; The melting point of the first insulator is lower than the melting point of the second insulator, The first insulator has a multi-layer structure, and at least one layer other than the layer closest to the first conductor is composed of a resin composition containing an insulating resin and a granular substance having a higher melting point than the insulating resin. The granular material is electrically conductive.

2. The multi-core cable according to claim 1, wherein: The heat detection line has a sleeve covering the surrounding of the twisted pair, The melting point of the sleeve is higher than that of the first insulator.

3. The multi-core cable according to claim 1 or 2, wherein: The plurality of electric wires are twisted in a spiral shape around the heat detection wire.

4. The multi-core cable according to claim 1 or 2, wherein: The first conductor is composed of a steel wire.

Images