Heat detection wire and multi-core cable

Abstract

A heat detection wire and a multi-core cable are provided, which can detect the temperature rise in the multi-core cable laid in a housing with high precision. A heat detection wire (2) includes 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), wherein the first conductor (211) is a non-magnetic material and is composed of a copper alloy with a tensile strength of 900 MPa or more.

Description

Technical Field

[0001] The invention relates to a heat detection wire and a multi-core cable. Background Art

[0002] Conventionally, fire detection wires have been used to detect fires (see, for example, Patent Document 1). These wires consist of a twisted pair of fire detection wires, each covered with a jacket. The wires comprise a conductor (made of steel wire, such as piano wire) and a low-melting-point insulator covering the conductor.

[0003] Conventionally, fire detection wires are arranged along cables. For example, in a multi-core cable used for contactless power supply, a fire detection wire is provided between the multi-core cable and a housing that houses 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] Multi-core cables installed within a housing, such as those used for contactless power supply, carry large currents through the wires within the cable. Therefore, if excessive currents flow through the wires for some reason, there is a need to prevent the temperature within the cable from rising and potentially causing a fire.

[0009] Therefore, an object of the present invention is to provide a heat detection wire and a multi-core cable capable of detecting a temperature rise in a multi-core cable installed in a housing with high accuracy.

[0010] Methods for solving problems

[0011] To solve the above-mentioned problems, the present invention provides a heat detection wire comprising a twisted pair of heat detection wires having a conductor and an insulator covering the conductor, wherein the conductor is a non-magnetic copper alloy having a tensile strength of 900 MPa or more.

[0012] In addition, for the purpose of solving the above-mentioned problems, the present invention provides a multi-core cable, which includes the above-mentioned heat detection wire, multiple electric wires and a sheath covering the above-mentioned heat detection wire and the above-mentioned multiple electric wires, and the melting point of the above-mentioned insulation of the above-mentioned heat detection wire is lower than the melting point of the insulation of the above-mentioned multiple electric wires.

[0013] Effects of the Invention

[0014] According to the present invention, it is possible to provide a heat detection wire and a multi-core cable capable of detecting a temperature rise in a multi-core cable laid in a housing with high accuracy. 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 of a multi-core cable housed in a groove of a housing.

[0018] Figure 4 The photographs are for explaining the operation of the heat detection wire 2 , (a) is a photograph before the operation, and (b) is a photograph after the operation.

[0019] Figure 5 This is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a multi-core cable according to a modified example of the present invention.

[0020] Explanation of symbols

[0021] 1: Multi-core cable; 2: Heat detection wire; 21: Heat detection wire; 211: First conductor (conductor); 212: First insulator (insulator); 22: Twisted pair; 23: Crimping tape; 24: Sleeve; 3: Wire; 31: Second conductor; 32: Second insulator; 4: Sheath. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0023] 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 longitudinal 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 of a multi-core cable housed in a groove of a housing.

[0024] To address the aforementioned issues, the present inventors considered integrating a heat detection wire for detecting temperature rises into a multi-core cable disposed within a housing. In this context, they focused on achieving high-precision detection of temperature rises within the multi-core cable while suppressing the reduction in contactless power supply efficiency caused by the heat detection wire. This led to the present invention.

[0025] 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 both the heat detection wire 2 and the plurality of electric wires 3 .

[0026] This multi-core cable 1 is used for contactless power supply (contactless power supply) and is housed in a slot 11 of a housing 10. In this example, the housing 10 includes a pair of parallel side walls 12 and a bottom wall 13 perpendicular to the side walls 12, connecting the ends of the side walls 12. The overall shape, as seen in a cross-sectional view, forms a "U" shape rotated 90 degrees clockwise. The rectangular space, defined by the pair of side walls 12 and the bottom wall 13 and open on the side opposite to the bottom wall 13, forms slot 11.

[0027] (Heat detection line 2)

[0028] The heat detection wire 2 includes a twisted pair 22 formed by twisting a pair of heat detection electric wires 21 , a compression tape 23 spirally wound around the twisted pair 22 , and a sleeve 24 covering the compression tape 23 .

[0029] The pair of heat detection wires 21 constituting the twisted pair 22 each includes a conductor (hereinafter referred to as a first conductor to distinguish them from the conductors of the wire 3 described later) 211 and an insulator (hereinafter referred to as a first insulator to distinguish them from the insulator of the wire 3 described later) 212 covering the first conductor 211. It is preferable that the first conductors 211 be a conductor that increases the force that causes the first conductors 211 to approach each other toward the center of the twisted pair 22 when the first conductors 211 are twisted together.

[0030] As described above, the multi-core cable 1 is used for contactless power supply and is wired in factories, etc., for example, over long distances of more than 30 m. Therefore, it is necessary to maintain the conductivity of the first conductor 211 at a high level to the extent that short circuits between the first conductors 211 can be detected even when wiring over long distances. In addition, strength is required to prevent disconnection even when wiring over long distances. In the heat detection wire 2 involved in this embodiment, the outer diameter of the first conductor 211 is preferably set to be greater than 0.5 mm and less than 1.0 mm. By setting the outer diameter of the first conductor 211 to be greater than 0.5 mm, the conductor resistance is suppressed and the high conductivity is maintained, so that short circuits between the first conductors 211 can be detected even when wiring over long distances. In addition, by setting the outer diameter of the first conductor 211 to be greater than 0.5 mm, the reduction in the force of the first conductors 211 trying to approach each other and the reduction in detection sensitivity can be suppressed, thereby improving the detection sensitivity of the temperature inside the cable. On the other hand, by setting the outer diameter of the first conductor 211 to be less than 1.0 mm, the multi-core cable 1 can be prevented from becoming hard and difficult to bend, thereby achieving a multi-core cable 1 that is easy to wire.

[0031] Furthermore, in the heat detection cable 2 according to this embodiment, a non-magnetic copper alloy with a tensile strength of 900 MPa or greater is used as the first conductor 211. More specifically, the first conductor 211 is made of phosphor bronze containing 7% to 9% tin and 0.03% to 0.35% phosphorus. Using a non-magnetic material as the first conductor 211 can suppress losses in contactless power supply and reduce the efficiency of contactless power supply. Furthermore, by setting the tensile strength of the first conductor 211 to 900 MPa or greater (preferably 930 MPa or greater, and more preferably 990 MPa or greater), the force exerted by the twisted first conductors 211 of the twisted pair 22 to move toward the center of the twisted pair 22 can be increased. As a result, when the first insulator 212 softens and melts, the first conductors 211 quickly move toward the center of the twisted pair 22, contacting each other. This contact improves the sensitivity of temperature detection within the cable. Furthermore, to increase the force exerted by the first conductors 211 of the twisted pair 22 toward the center of the twisted pair 22, thereby improving detection sensitivity, the elongation of the first conductor 211 is preferably 10% or less (more preferably 3% or less). In this embodiment, a single-wire first conductor 211 made of phosphor bronze with a diameter of 0.9 mm, a tensile strength of 998.9 MPa, and an elongation of 2.4% is used. Furthermore, by setting the tensile strength of the first conductor 211 to 900 MPa or greater, it is possible to ensure strength that prevents breakage even over long wiring distances. The tensile strength and elongation of the first conductor 211 were determined using a tensile test method based on JIS Z 2241 (2011) (test piece: 9B).

[0032] It should be noted that the copper alloy used for the first conductors 211 is not limited to phosphor bronze; for example, brass, beryllium copper, etc. may also be used. However, it is more preferable to use inexpensive phosphor bronze because it can increase the force that causes the first conductors 211 of the twisted pair 22 to approach each other toward the center of the twisted pair 22 and is less likely to cause disconnection.

[0033] As the first insulator 212, an insulating resin with a relatively low melting point is used to melt when the temperature within the cable rises. More specifically, the melting point of the first insulator 212 is lower than that of the second insulator 32 of the wire 3 (e.g., 105°C or higher). This allows the first insulator 212 to melt before the second insulator 32 (described later) of the wire 3 melts due to heat caused by an increase in the cable temperature, such as an overcurrent. In other words, this allows the detection of a temperature rise within the cable, such as an overcurrent caused by a short circuit in the first conductor 211, before the wire 3 loses function due to the heat of this temperature rise. In this embodiment, the melting point of the first insulator 212 is set to be higher than 80°C and lower than 100°C (preferably around 90°C), with the goal of not operating at temperatures below 80°C and operating within a few minutes (or less than 5 minutes) at 100°C. Here, the first insulator 212 is made of an ionomer resin with a melting point of approximately 89°C.

[0034] The thickness of the first insulator 212 is preferably set to be at least 0.1 mm and no more than 0.3 mm. By setting the thickness of the first insulator 212 to be at least 0.1 mm, the mechanical strength of the first insulator 212 can be ensured, and unwanted damage to the first insulator 212 can be suppressed, thereby preventing malfunction of the heat detection wire 2. In addition, by setting the thickness of the first insulator 212 to be no more than 0.3 mm, the first conductors 211 can quickly contact each other when the first insulator 212 softens or melts, thereby preventing the first conductors 211 from contacting each other even if the temperature inside the cable rises. In this embodiment, the thickness of the first insulator 212 is set to 0.15 mm, and the outer diameter of the heat detection wire 21 is set to 1.2 mm. The outer diameter of the twisted pair 22 formed by twisting the two heat detection wires 21 is 2.4 mm. It should be noted that the thickness of the first insulator 212 where the pair of heat detection wires 21 that make up the twisted pair 22 are in contact with each other (the portion where the first insulators 212 of the pair of heat detection wires 21 are in contact with each other) is preferably smaller than the thickness of the portion where the pair of heat detection wires 21 are not in contact with each other (the portion where the first insulators 212 of the pair of heat detection wires 21 are not in contact with each other). This allows the first conductors 211 to quickly contact each other when the first insulator 212 softens and melts, thus preventing the undesirable situation where the first conductors 211 do not contact each other even if the temperature inside the cable rises. In this case, it is preferable that the portion where the pair of heat detection wires 21 that make up the twisted pair 22 are in contact with each other is in surface contact. The thickness referred to here is the shortest distance (minimum thickness) from the inner surface of the first insulator 212 to the outer surface of the first insulator 212.

[0035] Figure 4 The following are photos illustrating the operation of the heat detection line 2. (a) is a photo before the operation, and (b) is a photo after the operation. Figure 4As shown in (a) and (b), in the heat detection line 2, the temperature inside the cable (the temperature around the wire 3) rises to a temperature above the melting point of the first insulator 212 (89°C in this embodiment) and below the melting point of the second insulator 32. If the first insulator 212 softens and melts due to the heat at this time, the first conductors 211 move toward the center of the twisted pair 22 due to the force of the twisted first conductors 211 trying to approach each other, and the first conductors 211 contact each other and are electrically short-circuited. At this time, the first insulator 212 is in a molten state. In addition, due to the force of the first conductors 211 trying to approach each other, the first insulator 212 existing in the gap between the first conductors 211 is pushed away from near the center of the twisted pair 22. Therefore, the outer shape of the first insulator 212 is no longer circular, so that the part where the first insulator 212 contacts each other is slightly flat. By detecting the short circuit of the two first conductors 211, the temperature rise in the multi-core cable 1 caused by overcurrent, etc. can be detected. It should be noted that Figure 4 In the photographs (a) and (b), the heat detection wire 2 is formed to be filled with epoxy resin to facilitate confirmation of the cross-sectional shape. The cut end face is polished and then photographed.

[0036] Therefore, in this heat detection line 2, before the two first conductors 211 short-circuit due to a rise in the temperature around the heat detection line 2, the first insulator 212 softens, the two first conductors 211 move closer together, and the resistance and capacitance between the two first conductors 211 change. Therefore, by measuring the resistance and capacitance between the two first conductors 211, a rise in the temperature around the heat detection line 2 can be detected before the two first conductors 211 short-circuit.

[0037] Although not shown in the figure, the first insulator 212 may have a multilayer structure comprising a plurality of layers of an insulating resin composition. For example, by providing the first insulator 212 with a two-layer structure and configuring the inner layer to have a higher melting point than the outer layer, it is possible to detect temperature increases within the multi-core cable 1 in a step-by-step manner.

[0038] Furthermore, when the first insulator 212 has a multilayer structure, at least one layer other than the layer closest to the first conductor 211 may contain a granular material having a higher melting point than the insulating resin constituting the first insulator 212. By including a granular material with a high melting point in the first insulator 212, when the temperature around the heat detection line 2 rises, the granular material is squeezed by the force of the first conductors 211 attempting to approach each other, thereby preventing the thin first insulator 212 from being left. This can facilitate short circuits between the first conductors 211. If the granular material is insulating, there is a possibility that the granular material will interlock between the first conductors 211, preventing a short circuit. Therefore, a conductive material is preferably used as the granular material. For example, carbon particles can be used as the granular material.

[0039] The twist pitch of the twisted pair 22 is preferably set to approximately 20 times (18 times to 22 times) the outer diameter of the heat detection wire 21. This maintains the force exerted by the first conductors 211 on the conductors 211, while preventing damage to the first insulator 212 caused by this force. The twist pitch of the twisted pair 22 is the distance between the heat detection wires 21 when they are circumferentially positioned at the same position along the length of the twisted pair 22. The outer diameter of the heat detection wire 21 is, for example, 1.0 mm to 1.6 mm.

[0040] A resin tape such as a polyester tape can be used as the pressure tape 23 wound around the twisted wire pair 22. The pressure tape 23 is spirally wound around the twisted wire pair 22 so that parts of the pressure tape 23 overlap in the width direction.

[0041] The sleeve 24 functions as a protective layer for the twisted pair 22. The melting point of the sleeve 24 is preferably higher than that of 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 formed by non-full extrusion molding (so-called tube extrusion molding).

[0042] Furthermore, in this embodiment, the sleeve 24 is made of an elastomer. In this embodiment, the heat detection wire 2 is positioned at the 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 pressed into the groove 11 of the housing 10. Furthermore, when the multi-core cable 1 is pressed, the wires 3 within the multi-core cable 1 are pressed toward the heat detection wire 2 positioned at the center of the cable. At this point, the sleeve 24 of the heat detection wire 2 elastically deforms due to the force exerted on the wires 3, allowing the wires 3 within the jacket 4 to move relative to the heat detection wire 2 in the circumferential and radial directions (directions around the heat detection wire 2 and along the outer diameter of the heat detection wire 2 in a cross-section of the multi-core cable 1 perpendicular to the cable's length). Therefore, the outer shape of the multi-core cable 1 can be modified according to the shape and size of the groove 11. Consequently, the multi-core cable 1 can easily fit into the groove 11 of the housing 10 even if its outer diameter increases.

[0043] In this way, the sleeve 24 of the heat detection line 2 undergoes elastic deformation, which plays a role in improving the operability when the multi-core cable 1 is housed in the groove 11. In addition, after the multi-core cable 1 is housed in the groove 11, the squeezing force from the wire 3 is relieved, so that the shape of the sleeve 24 is restored. At this time, due to the restoring force of the sleeve 24, the wire 3 in the sheath 4 acts in a manner of moving to the original position (the position before being housed in the groove 11). As a result, the multi-core cable 1 housed in the groove 11 is restored to its shape before deformation and remains in the groove 11. In this way, the sleeve 24 of the heat detection line 2 squeezes the sheath 4 toward the housing 10 (the inner wall of the groove 11) via the wire 3, and also plays a role in keeping the multi-core cable 1 in the groove 11.

[0044] All the wires 3 are in direct contact with the outer peripheral surface of the sleeve 24. That is, the outer peripheral surface of the heat detection line 2 is in direct contact with all the wires 3. As the sleeve 24, a sleeve made of an elastic material whose shape changes due to external force can be used, for example, a resin composition containing PVC (polyvinyl chloride) resin (heat-resistant vinyl resin) or polyurethane resin can be used. In this embodiment, the outer diameter of the sleeve 24 (that is, the outer diameter of the heat detection line 2) is set to 3.1 mm. It should be noted that, Figure 1 While (a) illustrates a configuration in which all of the wires 3 are in direct contact with the outer circumference of the sheath 24 (the outer circumference of the heat detection wire 2) in a cross section perpendicular to the longitudinal direction of the cable, this is not limited to this configuration. For example, in a multi-core cable 1 where no intervening material, described later, is placed between the heat detection wire 2 and the wires 3, any configuration may be sufficient as long as at least one of the wires 3 is in direct contact with the outer circumference of the sheath 24 (the outer circumference of the heat detection wire 2). However, from the perspective of arranging the multiple wires 3 in a balanced manner (at approximately equal intervals) around the heat detection wire 2, it is preferable that the outer circumference of the heat detection wire 2 be in direct contact with all of the wires 3.

[0045] The sleeve 24 is composed of a single layer or multiple layers. In the case of multiple layers, for example, the sleeve 24 is composed of an inner layer and an outer layer. The inner layer is arranged in such a way that its inner surface contacts the twisted pair 22. The outer layer is arranged in such a way that its inner surface contacts the inner layer. The outer layer contacts the wire 3 when the heat detection line 2 is arranged in the multi-core cable 1. That is, the outer peripheral surface of the outer layer becomes the outer peripheral surface of the sleeve 24. The thickness of the inner layer is preferably smaller than the thickness of the outer layer. The thickness of the inner layer is, for example, not less than 0.2 mm and not more than 0.4 mm. The thickness of the outer layer is, for example, not less than 0.2 mm and not more than 0.4 mm. Within this thickness range, the thickness of the outer layer can be made larger than the thickness of the inner layer. It should be noted that in this case, the overall thickness of the sleeve 24 is preferably, for example, not less than 0.4 mm and not more than 0.8 mm. In the multi-core cable 1, by configuring the sheath 24 of the heat detection wire 2 with a laminated structure composed of the aforementioned inner and outer layers, the overall thickness of the sheath 24 can be easily adjusted to a thickness that prevents the multiple wires 3 arranged around the heat detection wire 2 from falling toward the center of the cable. If the multiple wires 3 are less likely to fall toward the center of the cable, the multiple wires 3 can be arranged in a balanced manner (at substantially equal intervals) around the heat detection wire 2. This effectively improves the accuracy of heat detection in the heat detection wire 2 and the efficiency of contactless power supply to the wires 3.

[0046] Furthermore, the outer layer can have different properties, such as hardness and melting point, than the inner layer. For example, even if both the inner and outer layers are composed of a resin composition primarily composed of polyvinyl chloride resin, the outer and inner layers can have different hardnesses. In this case, the outer layer is preferably harder than the inner layer. This facilitates peeling the outer layer from the inner layer. Furthermore, the outer layer is preferably harder than the second insulator 32 constituting the wires 3. This prevents multiple wires 3 from falling into the center of the cable.

[0047] In addition, if Figure 5 As shown, the heat detection wire 2 may include a reinforcement layer 25 on the outer periphery of the sleeve 24. The reinforcement layer 25 forms a nearly circular cross-sectional shape of the heat detection wire 2 perpendicular to the longitudinal direction of the cable, and at the same time, when the heat detection wire 2 is arranged at the center of the cable, it plays a role in preventing the above-mentioned cross-sectional shape of the heat detection wire 2 from deforming. By having such a reinforcement layer 25, it is possible to prevent the multiple wires 3 from falling into the center of the cable. As a result, the multiple wires 3 arranged around the heat detection wire 2 can be arranged at approximately equal intervals relative to the circumferential direction of the cable, and the distance from the heat detection wire 2 to the center of each of the multiple wires 3 can be made approximately the same. It should be noted that with respect to the heat detection wire 2, when the outer periphery of the sleeve 24 includes a reinforcement layer 25, the reinforcement layer 25 becomes the outer surface of the heat detection wire 2, and the wires 3 are in direct contact with this outer surface.

[0048] As the reinforcing layer 25, for example, a tape layer formed by spirally winding a resin tape around the outer circumference of the sleeve 24, an extruded resin layer formed by extruding an insulating resin by tube extrusion, etc. can be used. When the reinforcing layer 25 is a tape layer, it can be a multi-layer structure. As a tape layer composed of multiple layers, for example, it can be a laminated structure consisting of an inner tape layer formed by spirally winding a resin tape around the outer circumference of the sleeve 24, and an outer tape layer formed by spirally winding a resin tape around the outer circumference of the inner tape layer. The winding directions of the resin tapes constituting the inner tape layer and the outer tape layer are preferably different. This makes it easier to exhibit the function of the reinforcing layer 25. The reinforcing layer 25 is preferably harder than the second insulator 32 constituting the electric wire 3. As the resin tape and insulating resin constituting the reinforcing layer 25, for example, polyethylene, fluororesin, etc. can be used.

[0049] (Wire 3)

[0050] Each of the electric wires 3 includes a second conductor 31 formed of a stranded conductor formed by collectively twisting a plurality of bare wires (collectively twisted), and a second insulator 32 covering the second conductor 31. Six electric wires 3 are constructed using the same structure. In this embodiment, 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 is preferably set to be not less than 0.15 mm and not more 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 protrude when the thickness of the second insulator 32 is reduced.

[0051] As a method for twisting bare wires, a method called co-core twisting is known. However, when the second conductor 31 is formed by this method, the bare wires are twisted in a stable state, and the shape of the second conductor 31 is unlikely to change due to external forces when the multi-core cable 1 is housed in the slot 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 housed in the slot 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 approximately 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.

[0052] In order to increase the cross-sectional area of the conductor portion in the multi-core cable 1, the thickness of the second insulator 32 of each wire 3 is preferably 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 will increase, resulting in an increase in the overall diameter of the multi-core cable 1. 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). It should be noted that, from the viewpoint of making the thickness as thin as possible, it is preferred that the second insulator 32 of each wire 3 is made of the same material and is composed of a single layer.

[0053] To achieve a higher capacity of power supply, the ratio of the outer diameter of the second conductor 31 to the outer diameter of the electric wire 3 is preferably set to 80% or greater. Furthermore, if the second insulator 32 is too thin, problems such as the bare wire piercing the second insulator 32 may occur, as described above. Therefore, the ratio of the outer diameter of the second conductor 31 to the outer diameter of the electric wire 3 is preferably set to 95% or less. Furthermore, to achieve a high capacity of power supply in a contactless manner, it is preferable to supply the same current to each of the second conductors 31 in the plurality of electric wires 3.

[0054] The second insulator 32 can be made of a material that can be thin-walled, is harder than the sleeve 24 to facilitate elastic deformation of the heat detection wire 2, and is resistant to external pressure (resistance to deformation due to external forces when the multi-core cable 1 is stored in the groove 11). For example, fluororesins such as ETFE (tetrafluoroethylene-ethylene copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), polyimide, and PEEK (polyetheretherketone) can be used. More preferably, a fluororesin with a smooth surface is used as the second insulator 32. This allows the wire 3 to more easily move within the jacket 4 when external force is applied, making it easier to insert into the groove 11 of the multi-core cable 1.

[0055] The second insulator 32 is formed by non-full extrusion (so-called tube extrusion). This prevents the second insulator 32 from being tightly attached to the bare wires, allowing them to move relative to each other within the second insulator 32. This makes it easier to deform the cross-sectional shape of the wires 3 when external forces are applied. This makes insertion into the slots 11 of the multi-core cable 1 easier.

[0056] (Collective 6)

[0057] A plurality of electric wires 3 are twisted in a spiral shape around the outer periphery of the heat detection wire 2. Hereinafter, a combination of the plurality of electric wires 3 twisted around the heat detection wire 2 is referred to as an aggregate 6.

[0058] When the number of wires 3 used in the assembly 6 is one to three, the multi-core cable 1 is less likely to deform due to external forces. Therefore, in the multi-core cable 1, the number of wires 3 used in the assembly 6 is set to four or more. In this embodiment, the number of wires 3 used in the assembly 6 is set to six, which allows for the thinnest outer diameter and the lowest total conductor resistance of all the wires 3.

[0059] In the assembly 6, adjacent wires 3 in the circumferential direction of the cable are in contact with each other. Furthermore, 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 allow contact with all six wires 3 when they are arranged without gaps in the circumferential direction of the cable. In this embodiment, the outer diameter of the heat detection wire 2 is set to be approximately the same as the outer diameter of the wires 3.

[0060] The twisting direction of the assembly 6 is preferably opposite to the twisting direction of the twisted pair 22 in the heat detection line 2. By making the twisting direction of the assembly 6 opposite to the twisting direction of the twisted pair 22, the twisting of the wire 3 is difficult to loosen, and the heat detection line 2 can be maintained in a state of being tightened by the wire 3. As a result, when the temperature in the cable rises, the first conductors 211 are easily in contact with each other due to the tightening of the wire 3, which can improve the detection sensitivity. It should be noted that the twisting direction of the assembly 6 is the direction in which the wire 3 rotates from the other end side to the first end side when the assembly 6 is observed from one end side. In addition, the twisting direction of the twisted pair 22 is the direction in which the heat detection wire 21 rotates from the other end side to the first end side when the twisted pair 22 is observed from one end side.

[0061] Furthermore, in this embodiment, the individual wires 3 constituting the assembly 6 are arranged so as to contact the inner circumferential surface of the sheath 4, and no crimping tape is wrapped around the assembly 6. This is because, if a tape were wrapped around the assembly 6, it would restrict the movement of the wires 3, potentially reducing ease of insertion of the multi-core cable 1 into the slot 11. It should be noted that, if maintaining the twisted state of the wires 3 is necessary for manufacturing convenience, a wire (resin thread, cotton thread, etc.) may be spirally wrapped around the assembly 6.

[0062] A filamentous intermediary can be arranged between the heat detection wire 2 and the multiple wires 3, and between the wires 3 and the sheath 4. In order to suppress the combustion of the intermediary due to the temperature rise in the cable, it is better to use a material with high heat resistance (at least a heat resistance temperature of 100°C or above). By having an intermediary, the overall shape of the multi-core cable 1 can be made close to a circle, thereby improving operability. It should be noted that, in the present embodiment, it is preferred that no filamentous intermediary is arranged between the heat detection wire 2 and the multiple wires 3, and between the wires 3 and the sheath 4. This is to suppress the combustion of the intermediary due to temperature rise, and to ensure a space (i.e., an air layer 5) in which the wires 3 can move in the circumferential direction and outer diameter direction of the heat detection wire 2 when an external force is applied to the cable 1.

[0063] (Sheath 4)

[0064] A sheath 4 is provided around the assembly 6. In the multi-core cable 1 according to this embodiment, the sheath 4 is formed by non-full extrusion (so-called tube extrusion). The sheath 4 is formed into a hollow cylindrical shape with a hollow portion 41 extending along its length. The heat detection wire 2 and the wires 3 (i.e., the assembly 6) are arranged within this hollow portion 41. This allows the wires 3 in the multi-core cable 1 to move relative to each other within the sheath 4.

[0065] Furthermore, as described above, in this embodiment, the wrapping tape is omitted, and the wires 3 are configured to be in direct contact with the inner circumferential surface of the sheath 4. The sheath 4 is preferably arranged so as to minimize the radial inward compression of the wires 3, and the contact area between the wires 3 and the sheath 4 is preferably minimized (point contact in a cross-sectional view).

[0066] The thickness of the sheath 4 is preferably set to be 0.6 mm or more and 1.0 mm or less. 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 be reduced; if the thickness of the sheath 4 is greater than 1.0 mm, the diameter of the multi-core cable 1 will increase.

[0067] Furthermore, the sheath 4 is formed by non-full extrusion molding and the thickness of the sheath 4 is made thinner than 1.0 mm, so that Figure 2 As shown, the outer surface of the sheath 4 is formed with projections and depressions so that the sheath 4 protrudes at the position of the wires 3. This makes it easier to press the multi-core cable 1 into the groove 11 of the housing 10 when inserting the multi-core cable 1. 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, making it easier to insert the multi-core cable 1 into the groove 11 of the multi-core cable 1. In this embodiment, a 0.8 mm thick polyvinyl chloride sheath is used as the sheath 4.

[0068] (Evaluation Test of Heat Detection Line 2)

[0069] A prototype heat detection wire 2 was produced as the first conductor 211. It was constructed of phosphor bronze (7-9 mass% tin, 0.03-0.35 mass% phosphorus, with the remainder being copper and trace amounts of unavoidable impurities) with a single wire diameter of 0.9 mm, a tensile strength of 998.9 MPa, and an elongation of 2.4%. Its operation was evaluated as an example. The heat detection wire 2 was installed in a thermostatic chamber at lengths of 80 m, 100 m, and 400 m. The lengths were measured until the first conductors 211 short-circuited. The chamber temperatures were set at 80°C, 100°C, 120°C, and 140°C.

[0070] Similarly, a heat detection wire for Comparative Example 1 was produced with the same configuration as the Example, except that phosphor bronze (5.5 mass% to 7 mass% tin, 0.03 mass% to 0.35 mass% phosphorus, the balance being copper and trace amounts of inevitable impurities) with a tensile strength of 891.0 MPa and an elongation of 2.3% was used as the first conductor 211. Evaluations were conducted in the same manner as for the Example. Furthermore, a heat detection wire for Comparative Example 2 was produced with the same configuration as for the Example, except that a copper alloy (approximately 0.7 mass% tin, the balance being copper and trace amounts of inevitable impurities) with a tensile strength of 676.7 MPa and an elongation of 1.9% to which tin was added was used. Evaluations were conducted in the same manner as for the Example. The first conductors 211 used in the Example and Comparative Examples 1 and 2 are summarized in Table 1.

[0071] [Table 1]

[0072] Conductor material Tensile strength [Mpa] Elongation [%] Conductivity [IACS%] Example Phosphor bronze 998.8 2.4 12.1 Comparative Example 1 Phosphor bronze 891.0 2.3 13.9 Comparative Example 2 Copper alloy with 0.7% tin 676.7 1.9 66.4

[0073] Evaluation of the heat detection wire 2 of the example and the heat detection wires of Comparative Examples 1 and 2 revealed that short circuits between the first conductors 211 did not occur in the heat detection wires of Comparative Examples 1 and 2 at any length or temperature, indicating that the heat detection wires did not operate normally. The measurement results for the heat detection wire 2 of the example are shown in Table 2.

[0074] [Table 2]

[0075]

[0076] As shown in Table 2, the heat detection wire 2 of the example did not operate at 80°C for 2 hours at any length, but operated at 100°C or higher for several minutes (generally within 3 minutes), confirming good operation.

[0077] (Functions and Effects of Implementation Methods)

[0078] As described above, in the heat detection wire 2 according to the present embodiment, the first conductor 211 is a non-magnetic body and is made of a copper alloy having a tensile strength of 900 MPa or more.

[0079] By configuring in this manner, it is possible to suppress a decrease in efficiency when built into a multi-core cable 1 for contactless power supply, suppress problems such as wire breakage even in the case of long-distance wiring, suppress a decrease in conductor resistance, and detect temperature increases in the cable with high precision.

[0080] (Summary of implementation methods)

[0081] Next, the technical ideas grasped from the above-described embodiments will be described by citing the reference symbols in the embodiments. However, the reference symbols in the following description do not limit the constituent elements in the claims to those specifically described in the embodiments.

[0082] [1] A heat detection wire (2) includes a twisted pair (22) formed by twisting a pair of heat detection wires (21) having a conductor (211) and an insulator (212) covering the conductor (211), wherein the conductor (211) is a non-magnetic material and is composed of a copper alloy with a tensile strength of 900 MPa or more.

[0083] [2] According to the heat detection wire (2) described in [1], in the pair of heat detection wires (21), when the insulator (212) softens or melts at a predetermined temperature, the conductors (211) move toward the center of the twisted pair (22) due to the force of the conductors (211) trying to approach each other, and the conductors (211) come into contact with each other.

[0084] [3] According to the heat detection wire (2) described in [2], the melting point of the above-mentioned insulator (212) is higher than 80°C and lower than 100°C, and the short circuit does not occur in an environment of 80°C, and the above-mentioned short circuit occurs within 5 minutes in an environment of 100°C.

[0085] [4] According to any one of [1] to [3], the conductor (211) is made of phosphor bronze containing 7 mass% to 9 mass% of tin and 0.03 mass% to 0.35 mass% of phosphorus.

[0086] [5] The heat detection wire (2) according to any one of [1] to [4], wherein the elongation of the conductor (211) is 10% or less.

[0087] [6] According to any one of [1] to [5], the heat detection wire (2) is surrounded by a sleeve (24), and the sleeve (24) has an inner layer and an outer layer, and the thickness of the outer layer is greater than the thickness of the inner layer.

[0088] [7] According to any one of the heat detection wires (2) described in [1] to [6], the twisted pair (22) is covered by a sleeve (24), and the sleeve (24) has a reinforcement layer (25) around it, and the reinforcement layer (25) is a tape layer formed by spirally winding a resin tape around the sleeve (24).

[0089] [8] A multi-core cable (1) comprising a heat detection wire (2) as described in any one of [1] to [7], a plurality of electric wires (3), and a sheath (4) covering the heat detection wire (2) and the plurality of electric wires (3), wherein the melting point of the insulation (212) of the heat detection wire (2) is lower than the melting point of the insulation (32) of the plurality of electric wires (3).

[0090] [9] According to the multi-core cable (1) described in [8], the plurality of electric wires (3) are twisted in a spiral shape around the heat detection wire (2).

[0091] While the embodiments of the present invention have been described above, the embodiments described above do not limit the invention as defined in the claims. Furthermore, it should be noted that the feature combinations described in the embodiments are not necessarily required to solve the problems of the invention. Furthermore, the present invention may be implemented with appropriate modifications without departing from its spirit.

Claims

1. A heat detection line, A twisted pair of heat detection wires comprising a pair of conductors and an insulator covering the conductors, The conductor is a non-magnetic body and is made of a copper alloy with a tensile strength of 900 MPa or more. The conductor is made of phosphor bronze containing more than 7 mass % and less than 9 mass % of tin and more than 0.03 mass % and less than 0.35 mass % of phosphorus.

2. The heat detection wire according to claim 1, wherein In the pair of heat detecting wires, when the insulator softens or melts at a predetermined temperature, the conductors move toward the center of the twisted pair due to a force that causes the conductors to approach each other, and the conductors come into contact with each other.

3. The heat detection wire according to claim 2, wherein: The melting point of the insulator is higher than 80° C. and lower than 100° C., and short circuit does not occur in an environment of 80° C., but short circuit occurs within 5 minutes in an environment of 100° C.

4. The heat detection wire according to any one of claims 1 to 3, wherein The conductor has an elongation of 10% or less.

5. The heat detection wire according to any one of claims 1 to 3, wherein The twisted pair is covered by a sleeve having an inner layer and an outer layer. The outer layer has a thickness greater than that of the inner layer.

6. The heat detection wire according to any one of claims 1 to 3, wherein The twisted pair is covered by a sleeve, and a reinforcement layer is provided around the sleeve. The reinforcement layer is a tape layer formed by spirally winding a resin tape around the sleeve.

7. A multi-core cable, A device comprising the heat detection wire according to any one of claims 1 to 6, a plurality of electric wires, and a sheath covering both the heat detection wire and the plurality of electric wires. The melting point of the insulator of the heat detection wire is lower than the melting points of the insulators of the plurality of electric wires.

8. The multi-core cable according to claim 7, wherein: The plurality of electric wires are twisted in a spiral shape around the heat detection wire.

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