Multi-core cable

Abstract

To provide a multi-core cable that is laid within a housing and can detect temperature rise in the cable.SOLUTION: The present invention provides a multi-core cable with a detection electric wire that can detect temperature rise in the cable. A plurality of wires is twisted together in contact with each other along the cable's circumferential direction around the cable's center. A sheath covering the plurality of wires is provided. The plurality of the wires includes a stranded wire conductor formed by collectively twisting a plurality of strands, and an insulator covering the stranded wire conductor. The stranded wire conductor has a cross-sectional shape perpendicular to the cable's longitudinal direction, where a width along the cable's circumferential direction gradually increases from a radially inward portion to a radially outward portion.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a multi-conductor cable. [Background technology]

[0002] Conventionally, fire detection wires have been used to detect fires (see, for example, Patent Document 1). The fire detection wire has a twisted pair formed by twisting together a pair of fire detection electric wires, each of which has a conductor made of a steel wire such as a piano wire and a low-melting-point insulator covering the conductor, and is configured so that the twisted pair is covered with a jacket.

[0003] Conventionally, a fire detection wire is arranged along a cable. 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 58-86695 Summary of the Invention [Problem to be solved by the invention]

[0005] In a multi-core cable laid inside a housing, for example, when used for contactless power supply, a large current flows through the electric wires arranged inside the multi-core cable. Therefore, there is a demand for suppressing a rise in temperature inside the multi-core cable that may lead to a fire if an excessive current flows through the electric wires for some reason.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a multi-core cable that is laid inside a housing and is capable of detecting a temperature rise inside the cable. [Means for solving the problem]

[0007] The present invention aims to solve the above-mentioned problems and provides a multi-core cable having a detection wire capable of detecting a temperature rise within the cable, wherein a plurality of electric wires are twisted together around a cable center in a circumferential direction of the cable while being in contact with each other, and a sheath is provided to cover the plurality of electric wires, and the plurality of electric wires have a stranded conductor formed by collective twisting a plurality of elemental wires, and an insulator that covers the stranded conductor, and the stranded conductor has a cross-sectional shape perpendicular to the cable longitudinal direction such that the width along the cable circumferential direction gradually increases from the inside to the outside in the cable radial direction. Effect of the Invention

[0008] According to the present invention, it is possible to provide a multi-core cable that is laid inside a housing and is capable of detecting a temperature rise inside the cable. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2A is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a multi-core cable according to one embodiment of the present invention, and FIG. 2B is a cross-sectional view showing a cross section perpendicular to the longitudinal direction of a heat detection line. [Diagram 2] 1 is a photograph showing a cross section of a multi-core cable perpendicular to the longitudinal direction of the cable. [Diagram 3] 1 is a cross-sectional view of a multi-core cable accommodated in a groove in a housing. [Figure 4] These are photographs explaining the operation of the thermal detection line, (a) being before operation and (b) being after operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Embodiment Mode] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0011] Fig. 1(a) is a cross-sectional view showing a cross-section perpendicular to the cable longitudinal direction of a multi-core cable according to this embodiment, and Fig. 1(b) is a cross-sectional view showing a cross-section perpendicular to the cable longitudinal direction of a heat detection line. Fig. 2 is a photograph showing a cross-section perpendicular to the cable longitudinal direction of a multi-core cable. Fig. 3 is a cross-sectional view of the multi-core cable accommodated in a groove of a housing. In the photograph of Fig. 2, in order to make it easier to confirm the cross-sectional state of the multi-core cable, epoxy resin is filled around the multi-core cable and around the heat detection line, and the cut end surface was polished before the cut surface was photographed.

[0012] As shown in FIGS. 1 to 3, the multi-core cable 1 includes a heat detection wire 2, a plurality of electric wires 3, and a sheath 4 that collectively covers the heat detection wire 2 and the plurality of electric wires 3.

[0013] This multi-core cable 1 is used to supply power contactlessly (for contactless power feeding), and is housed in a groove 11 of a housing 10 for use. In this example, the housing 10 has a pair of side walls 12 arranged in parallel, and a bottom wall 13 perpendicular to the side walls 12 that connects the ends of the side walls 12, and is formed into a U-shape rotated 90 degrees clockwise in a cross-sectional view as a whole. The groove 11 is a space that is surrounded by the pair of side walls 12 and the bottom wall 13 and has a rectangular shape in a cross-sectional view that opens to the side opposite the bottom wall 13.

[0014] (Thermal detection wire 2) The heat detection wire 2 has a twisted pair wire 22 formed by twisting a pair of heat detection electric wires 21, a pressure winding tape 23 wound spirally around the twisted pair wire 22, a jacket 24 covering the pressure winding tape 23, and a reinforcing layer 25 covering the jacket 24.

[0015] Each of the pair of heat detection wires 21 constituting the twisted pair 22 has a first conductor 211 and a first insulator 212 covering the periphery of the first conductor 211. It is preferable to use a first conductor 211 that can increase the force that causes the first conductors 211 to approach each other toward the center of the twisted pair 22 when they are twisted together to form the twisted pair 22.

[0016] As described above, the multi-core cable 1 is used for contactless power supply, and is wired over a long distance, for example, 30 m or more, in a factory or the like. Therefore, it is necessary to maintain the conductivity of the first conductor 211 high enough to detect a short circuit between the first conductors 211 even when wired over a long distance. In addition, strength is required that does not cause disconnection even when wired over a long distance. In this embodiment, the outer diameter of the first conductor 211 is preferably 0.5 mm or more and 1.0 mm or less. By setting the outer diameter of the first conductor 211 to 0.5 mm or more, the conductor resistance is suppressed and the conductivity is maintained high, making it possible to detect a short circuit between the first conductors 211 even when wired over a long distance. In addition, by setting the outer diameter of the first conductor 211 to 0.5 mm or more, it is possible to suppress a decrease in the force that causes the first conductors 211 to approach each other, which reduces the detection sensitivity, and improves the detection sensitivity of the temperature inside the cable. On the other hand, by setting the outer diameter of first conductors 211 to 1.0 mm or less, multi-core cable 1 can be prevented from becoming stiff and difficult to bend, and a multi-core cable 1 that is easy to wire can be realized.

[0017] Furthermore, in this embodiment, the first conductor 211 is made of a non-magnetic copper alloy having a tensile strength of 900 MPa or more. More specifically, the first conductor 211 is made of phosphorus bronze containing 7 mass% or more and 9 mass% or less of tin and 0.03 mass% or more and 0.35 mass% or less of phosphorus. By using a non-magnetic material as the first conductor 211, it is possible to suppress loss in non-contact power supply and suppress a decrease in efficiency of non-contact power supply. Furthermore, by making the tensile strength of the first conductor 211 900 MPa or more (preferably 930 MPa or more, more preferably 990 MPa or more), it is possible to increase the force with which the first conductors 211 of the twisted pair wire 22 move toward each other toward the center side of the twisted pair wire 22 in a state in which the first conductors 211 of the twisted pair wire 22 are twisted together. As a result, when the first insulator 212 softens or melts, the first conductors 211 move quickly toward the center of the twisted pair 22, and the first conductors 211 come into contact with each other, which makes it possible to improve the detection sensitivity of the temperature inside the cable. In addition, from the viewpoint of increasing the force that the first conductors 211 of the twisted pair 22 try to approach each other toward the center of the twisted pair 22 and improving the detection sensitivity, it is desirable that the elongation of the first conductor 211 is 10% or less (more preferably 3% or less). In this embodiment, the first conductor 211 is made of phosphor bronze with a diameter of 0.9 mm, and is a solid wire with a tensile strength of 998.9 MPa and an elongation of 2.4%. In addition, by making the tensile strength of the first conductor 211 900 MPa or more, it is possible to ensure a strength that does not cause breakage even when the first conductor 211 is wired over a long distance. The tensile strength and elongation of the first conductor 211 are obtained by a tensile test method (test piece: No. 9B) in accordance with JISZ2241 (2011).

[0018] The copper alloy used for the first conductors 211 is not limited to phosphor bronze, and for example, brass, beryllium copper, etc. may also be used. However, it is more desirable to use phosphor bronze, which 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, is less likely to break, and is inexpensive.

[0019] For the first insulator 212, an insulating resin with a relatively low melting point is used so that it melts when the temperature inside the cable rises due to an overcurrent or the like. More specifically, the melting point of the first insulator 212 is set lower than the melting point of the second insulator 32 of the electric wire 3 (for example, 105°C or higher) so that the first insulator 212 melts before the second insulator 32 (described later) of the electric wire 3 melts due to heat when the temperature inside the cable rises due to an overcurrent or the like (in other words, the first conductor 211 is short-circuited so that a temperature rise inside the cable due to the occurrence of an overcurrent or the like is detected before the function of the electric wire 3 is lost due to heat at the time of the above-mentioned temperature rise). In this embodiment, the melting point of the first insulator 212 is set higher than 80°C and lower than 100°C (more preferably, about 90°C) with the aim of not operating at 80°C or lower but operating at 100°C for several minutes (within 5 minutes). Here, the first insulator 212 made of an ionomer resin with a melting point of about 89°C is used.

[0020] The thickness of the first insulator 212 is preferably 0.1 mm or more and 0.3 mm or less. By making the thickness of the first insulator 212 0.1 mm or more, the mechanical strength of the first insulator 212 is ensured, and unintended damage to the first insulator 212 is suppressed, thereby suppressing malfunction of the heat detection wire 2. Furthermore, by making the thickness of the first insulator 212 0.3 mm or less, the first conductors 211 are quickly brought into contact with each other when the first insulator 212 softens or melts, and a problem in which the first conductors 211 do not come into contact with each other even though the temperature inside the cable is rising can be suppressed. In this embodiment, the thickness of the first insulator 212 is 0.15 mm, and the outer diameter of the heat detection wire 21 is 1.2 mm. The outer diameter of the twisted pair wire 22 in which two heat detection wires 21 are twisted together is 2.4 mm. In addition, the thickness of the first insulator 212 at a portion where the pair of heat detection electric wires 21 constituting the twisted pair 22 contact each other (a portion where the first insulators 212 of the pair of heat detection electric wires 21 contact each other) is preferably smaller than the thickness of a portion where the pair of heat detection electric wires 21 do not contact each other (a portion where the first insulators 212 of the pair of heat detection electric wires 21 do not contact each other). This makes it possible to quickly bring the first conductors 211 into contact with each other when the first insulator 212 softens or melts, and to easily suppress a problem in which the first conductors 211 do not contact each other even though the temperature inside the cable is rising. In this case, it is preferable that the portions where the pair of heat detection electric wires 21 constituting the twisted pair 22 contact each other are 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.

[0021] 4 is a photograph for explaining the operation of the heat detection wire 2, (a) is a photograph before operation, and (b) is a photograph after operation. As shown in Fig. 4(a) and (b), in the heat detection wire 2, the temperature inside the cable (the temperature around the electric wire 3) rises to a temperature equal to or higher than the melting point of the first insulator 212 (89°C in this embodiment) and lower than the melting point of the second insulator 32, and when 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 toward the center of the twisted pair 22, and the first conductors 211 come into contact with each other and are electrically short-circuited. At this time, the first insulators 212 are in a molten state, and the first insulators 212 present between the first conductors 211 are pushed away from the vicinity of the center of the twisted pair 22 due to the force of the first conductors 211 trying to approach each other. Therefore, the outer shape of the first insulators 212 is not circular, but the portions where the first insulators 212 contact each other are slightly flattened. By detecting a short circuit between the two first conductors 211, it is possible to detect a temperature rise in the multi-core cable 1 due to an overcurrent or the like. In the photographs of Figures 4(a) and (b), the heat detection wire 2 is filled with epoxy resin in order to make it easier to confirm the cross-section of the heat detection wire 2, and the cut end surface was polished before photographing the cut surface. In addition, the reinforcing layer 25 is omitted in Figures 4(a) and (b).

[0022] Incidentally, in this heat detection wire 2, when the temperature around the heat detection wire 2 rises, the first insulator 212 softens and the distance between the two first conductors 211 decreases before the two first conductors 211 are shorted, causing a change in the resistance value and capacitance between the two first conductors 211. Therefore, by measuring the resistance value and capacitance between the two first conductors 211, it is possible to detect a rise in the temperature around the heat detection wire 2 before the two first conductors 211 are shorted.

[0023] Although not shown, first insulator 212 may have a multi-layer structure in which a plurality of layers made of an insulating resin composition are laminated. For example, first insulator 212 may have a two-layer structure in which the melting point of the inner layer is made higher than the melting point of the outer layer, whereby a temperature rise in multi-core cable 1 can be detected in stages.

[0024] Furthermore, when the first insulator 212 has a multi-layer structure, at least one layer other than the layer closest to the first conductor 211 may contain a particulate material having a higher melting point than the insulating resin constituting the first insulator 212. By containing a particulate material having a high melting point in the first insulator 212, when the temperature around the heat detection line 2 rises, the particulate material is pushed in by the force of the first conductors 211 trying to approach each other, and the first insulator 212 is prevented from remaining thin, making it easier to cause a short circuit between the first conductors 211. If the particulate material is insulating, there is a risk that the particulate material will be caught between the first conductors 211 and a short circuit will not occur, so it is desirable to use a conductive particulate material. For example, carbon particles can be used as the particulate material.

[0025] The twist pitch of the twisted pair wires 22 is preferably about 20 times (18 times or more and 22 times or less) the outer diameter of the heat detection electric wires 21. This makes it possible to maintain the force that brings the first conductors 211 closer to each other while preventing the first insulators 212 from being destroyed by this force. The twist pitch of the twisted pair wires 22 is the interval between longitudinal positions at which any of the heat detection electric wires 21 are at the same circumferential position in the longitudinal direction of the twisted pair wires 22. The outer diameter of the heat detection electric wires 21 is, for example, 1.0 mm or more and 1.6 mm or less.

[0026] A resin tape such as a polyester tape can be used as the pressure winding tape 23 that is wound around the twisted pair wires 22. The pressure winding tape 23 is wound spirally around the twisted pair wires 22 so that parts of the pressure winding tape 23 overlap each other in the width direction.

[0027] The jacket 24 serves as a protective layer that protects the twisted pair wires 22. It is desirable that the melting point of the jacket 24 is higher than the melting point of the first insulator 212 so that the jacket 24 does not melt before the first insulator 212 melts. The jacket 24 is made of an insulating resin and is formed by non-solid extrusion molding (so-called tube extrusion molding).

[0028] In this embodiment, the jacket 24 is made of an elastic body. In this embodiment, the heat detection wire 2 is arranged at the cable center of the multi-core cable 1. When the multi-core cable 1 is accommodated in the groove 11, the multi-core cable 1 is accommodated in the groove 11 by pressing the multi-core cable 1 into the groove 11 of the housing 10. When the multi-core cable 1 is pressed, the electric wire 3 in the multi-core cable 1 is pressed against the heat detection wire 2 arranged at the cable center. At this time, the jacket 24 of the heat detection wire 2 is elastically deformed by the force when the electric wire 3 is pressed, and the electric wire 3 in the sheath 4 can move relative to each other in the circumferential direction and radial direction of the heat detection wire 2 (in the cross section perpendicular to the cable longitudinal direction of the multi-core cable 1, in the direction along the periphery of the heat detection wire 2 and the direction along the outer diameter of the heat detection wire 2). Therefore, the outer shape of the multi-core cable 1 can be deformed according to the shape and dimensions of the groove 11. This makes it easier to insert the multi-core cable 1 into the groove 11 of the housing 10 even if its outer diameter becomes thicker.

[0029] In this way, the jacket 24 of the heat detection wire 2 elastically deforms to improve the workability when accommodating the multi-core cable 1 in the groove 11. After the multi-core cable 1 is accommodated in the groove 11, the jacket 24 restores its shape as the pressing force from the electric wires 3 is alleviated. The restoring force of the jacket 24 at this time acts to move the electric wires 3 in the sheath 4 to their original position (the position before being accommodated in the groove 11). As a result, the multi-core cable 1 accommodated in the groove 11 is restored to its pre-deformation outer shape and is held in the groove 11. In this way, the jacket 24 of the heat detection wire 2 also serves to press the sheath 4 against the housing 10 (the inner wall of the groove 11) via the electric wires 3, thereby holding the multi-core cable 1 in the groove 11.

[0030] The jacket 24 may be made of an elastic material that changes shape when subjected to an external force, for example, a resin composition made of PVC (polyvinyl chloride) resin (heat-resistant vinyl resin) or urethane resin. In this embodiment, the outer diameter of the jacket 24 is 3.1 mm.

[0031] The jacket 24 is made of a single layer or multiple layers. In the case of multiple layers, for example, the jacket 24 is made of an inner layer and an outer layer. The inner layer is provided so that its inner surface is in contact with the twisted pair wire 22. The outer layer is provided so that its inner surface is in contact with the inner layer. The outer surface of the outer layer is in contact with the reinforcing layer 25. The thickness of the inner layer is preferably smaller than that of the outer layer. The thickness of the inner layer is, for example, 0.2 mm or more and 0.4 mm or less. The thickness of the outer layer is, for example, 0.2 mm or more and 0.4 mm or less. In this thickness range, it is preferable that the thickness of the outer layer is larger than that of the inner layer. In this case, the overall thickness of the jacket 24 is, for example, 0.4 mm or more and 0.8 mm or less. In the multi-core cable 1, the jacket 24 of the heat detection wire 2 has a laminated structure consisting of the inner layer and the outer layer described above, so that the overall thickness of the jacket 24 can be easily adjusted to a thickness that makes it difficult for the multiple electric wires 3 arranged around the heat detection wire 2 to fall into the center of the cable. If the multiple electric wires 3 are less likely to fall into the center of the cable, the multiple electric wires 3 can be arranged in a balanced manner (at approximately equal intervals) around the heat detection wire 2, and it is also possible to uniform the cross-sectional shape of the electric wires 3 (cross-sectional shape of the second conductor 31) described later. This is effective in improving the accuracy of heat detection in the heat detection wire 2 and the efficiency of contactless power supply to the electric wires 3.

[0032] The outer layer may have properties such as hardness and melting point different from those of the inner layer. For example, even if both the outer layer and the inner layer are made of a resin composition mainly composed of polyvinyl chloride resin, the outer layer and the inner layer have different hardnesses. In this case, the hardness of the outer layer is preferably harder than that of the inner layer. This makes it easier to peel the outer layer from the inner layer. In addition, the hardness of the outer layer is preferably harder than that of the second insulator 32 constituting the electric wire 3. This makes it harder for the multiple electric wires 3 to fall toward the center of the cable, and makes it possible to uniform the cross-sectional shape of the electric wire 3 (cross-sectional shape of the second conductor 31) described later.

[0033] The reinforcing layer 25 serves to make the cross-sectional shape of the heat detection wire 2 perpendicular to the cable longitudinal direction substantially circular, and to make the cross-sectional shape of the heat detection wire 2 less likely to deform when the heat detection wire 2 is disposed at the center of the cable. By providing such a reinforcing layer 25, it is possible to prevent the plurality of electric wires 3 from dropping to the center of the cable. This allows the plurality of electric wires 3 disposed around the heat detection wire 2 to be disposed at substantially equal intervals in the cable circumferential direction, and also allows the distances from the heat detection wire 2 to the centers of the plurality of electric wires 3 to be substantially the same. Furthermore, in this embodiment, the plurality of electric wires 3 are pressed against the heat detection wire 2 and deformed into a non-circular shape, but by providing the reinforcing layer 25, it is possible to make the cross-sectional shape of each of the plurality of electric wires 3 uniform (details will be described later).

[0034] The reinforcing layer 25 may be, for example, a tape layer formed by winding a resin tape in a spiral shape around the outer periphery of the jacket 24, or an extruded resin layer formed by extruding an insulating resin by tube extrusion. When the reinforcing layer 25 is a tape layer, it may be multi-layered. The multi-layered tape layer may be, for example, a laminated structure of an inner layer tape layer formed by winding a resin tape in a spiral shape around the outer periphery of the jacket 24, and an outer layer tape layer formed by winding a resin tape in a spiral shape around the outer periphery of the inner layer tape layer. The winding directions of the resin tapes constituting the inner layer tape layer and the outer layer tape layer are preferably different directions. This makes it easier to realize the role of the reinforcing layer 25 described above. The reinforcing layer 25 is preferably harder than the second insulator 32 constituting the electric wire 3. For example, polyethylene, fluororesin, etc. may be used as the resin tape and insulating resin constituting the reinforcing layer 25. In this embodiment, a resin tape made of polyethylene is used as the inner layer tape layer and the outer layer tape layer, and the reinforcing layer 25 is formed by winding the resin tape made of polyethylene twice.

[0035] A plurality of electric wires 3 are in direct contact with the outer surface of the reinforcing layer 25, i.e., the outer surface of the heat detection wire 2. In this embodiment, at least one electric wire 3 is in surface contact with the outer surface of the heat detection wire 2. The electric wire 3 is pressed against the heat detection wire 2 and in close contact with it, and a part of the outer surface of the electric wire 3 (a radially inner part) is deformed into an arc shape along the outer surface of the heat detection wire 2. This makes it easier for the heat detection wire 2 and the electric wire 3 to be in close contact with each other, and makes it possible for the heat detection wire 2 to quickly detect a temperature rise of the electric wire 3. In addition, by pressing the electric wire 3 against the heat detection wire 2, the first conductors 211 are more likely to come into contact with each other when the temperature inside the cable rises, and it is possible to improve the detection sensitivity.

[0036] In Fig. 1(a), all the electric wires 3 are in surface contact with the outer surface of the heat detection wire 2 in the cross section perpendicular to the longitudinal direction of the cable, but the present invention is not limited to this. For example, as shown in the photograph of Fig. 2, it is sufficient that at least one electric wire 3 is in surface contact with the outer surface of the heat detection wire 2. However, from the viewpoint of arranging the multiple electric wires 3 in a balanced manner (at substantially equal intervals) around the heat detection wire 2 and from the viewpoint of quickly detecting a temperature rise of the electric wires 3, it is more preferable that the outer surface of the heat detection wire 2 is in direct contact with as many electric wires 3 as possible (more preferably, all the electric wires 3).

[0037] (Electric wire 3) The electric wire 3 has a second conductor 31 made of a stranded conductor formed by bunching together a plurality of strands, and a second insulator 32 covering the second conductor 31. The six electric wires 3 have the same structure. In this embodiment, a tin-plated soft copper wire is used as the strand used for the second conductor 31. The outer diameter of the strand used for the second conductor 31 is preferably 0.15 mm or more and 0.32 mm or less. This is because if the outer diameter of the strand is less than 0.15 mm, it is likely to break, and if it exceeds 0.32 mm, it may break through the second insulator 32 when the second insulator 32 is made thinner.

[0038] A method called concentric twisting is known as a method for twisting wires, but if the second conductor 31 is formed by this method, the wires are twisted in a stable state, and the shape of the second conductor 31 is unlikely to change due to the external force when the multi-core cable 1 is accommodated in the groove 11. For this reason, the second conductor 31 is formed by bunch twisting so that the shape of the second conductor 31 is likely to change due to the external force when the multi-core cable 1 is accommodated in the groove 11. In this embodiment, 134 0.26 mm wires are bunch twisted to form a conductor with a cross-sectional area of ​​7 mm. 2 More than 8mm 2 The following second conductors 31 were formed.

[0039] In order to increase the cross-sectional area of ​​the conductor portion in the multi-core cable 1, it is desirable that the second insulator 32 of each electric wire 3 is as thin as possible. More specifically, the thickness of the second insulator 32 is preferably 1 / 2 to 1 times the outer diameter of the wire used in the second conductor 31. If the thickness of the second insulator 32 is less than 1 / 2 the outer diameter of the wire, the wire may break through the second insulator 32 due to an external force when the multi-core cable 1 is accommodated in the groove 11, and if the thickness exceeds 1 time the outer diameter of the wire, the electric wire 3 becomes large in diameter, which leads to 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 wire). In order to make the thickness as thin as possible, it is preferable that the second insulator 32 of each electric wire 3 is made of the same material and is made of a single layer. In order to enable a large-capacity power supply in a non-contact manner, it is preferable that the second conductors 31 of the multiple electric wires 3 each supply a current of the same magnitude.

[0040] The second insulator 32 may be made of a material that can be thin-walled, is harder than the jacket 24 of the heat detection line 2 to facilitate elastic deformation of the jacket 24, and is resistant to external pressure (is less likely to deform due to external force when the multi-core cable 1 is accommodated in the groove 11), and examples of such materials include fluororesins such as ETFE (tetrafluoroethylene-ethylene copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PTFE (polytetrafluoroethylene), and PVDF (vinylidene prefluoride), as well as polyimide and PEEK (polyether ether ketone). More preferably, the second insulator 32 may be made of a fluororesin with a smooth surface, which allows the electric wire 3 to move more easily in the sheath 4 when an external force is applied, making it easier to insert the multi-core cable 1 into the groove 11.

[0041] The second insulator 32 is formed by non-solid extrusion (so-called tube extrusion). This means that the second insulator 32 is not in close contact with the wires, allowing the wires to move relative to each other within the second insulator 32, making it easier for the cross-sectional shape of the electric wire 3 to deform when an external force is applied. This makes it easier to insert the multi-core cable 1 into the groove 11.

[0042] In the multi-core cable 1 according to the present embodiment, the second conductor 31 is formed so that the cross-sectional shape perpendicular to the cable longitudinal direction is non-circular. More specifically, the second conductor 31 is formed so that the width along the circumferential direction gradually increases from the radially inner side to the radially outer side, and is formed in a substantially fan shape. This allows the cross-sectional area of ​​the second conductor 31 to be as large as possible in the limited space in the sheath 4. In addition, the current flowing through the second conductor 31 mainly flows through the outer portion of the second conductor 31 in the cable radial direction (the outer peripheral portion, i.e., the periphery of the outer peripheral portion 3c described later). However, by forming the second conductor 31 so that the width along the circumferential direction gradually increases from the radially inner side to the radially outer side, the second conductor 31 (cross-sectional area and surface area) in the outer peripheral portion where the current is concentrated can be increased. This allows the multi-core cable 1 to suppress the current loss in the second conductor 31, and contribute to improving the efficiency of contactless power supply.

[0043] The electric wire 3 has a non-circular cross-sectional shape including the second conductor 31 as a whole due to pressing by the sheath 4 described later. More specifically, a part of the outer surface of the electric wire 3 becomes a heat detection wire contact portion 3a that is in surface contact with the outer surface of the heat detection wire 2. The heat detection wire contact portion 3a is a substantially arc-shaped surface along the outer surface of the heat detection wire 2. In addition, in the multi-core cable 1, the electric wires 3 adjacent to each other in the circumferential direction are also in surface contact with each other, and this surface contact portion becomes a substantially flat electric wire contact portion 3b. The electric wire contact portion 3b is a flat surface that is substantially along the cable diameter direction in a cross section perpendicular to the cable longitudinal direction. Furthermore, a part of the outer surface of the electric wire 3 becomes an outer periphery portion 3c that is formed in a shape that is along the inner surface of the sheath 4 in a cross section perpendicular to the cable longitudinal direction. In the present embodiment, the outer periphery portion 3c is in direct contact with the inner surface of the sheath 4 and is a substantially arc-shaped surface that is along the inner surface of the sheath 4. However, the outer circumferential portion 3c does not need to be in direct contact with the sheath 4, and may be in contact with the inner surface of the sheath 4 via, for example, a pressure winding tape that is spirally wound around the electric wire 3.

[0044] It is desirable that the external shape (cross-sectional shape) of the heat detection wire 2 is as close to a circle as possible so that all the electric wires 3 are evenly deformed by the pressure of the sheath 4. This is because if the external shape of the heat detection wire 2 arranged at the center of the cable is, for example, elliptical or uneven, the external shapes of the electric wires 3 arranged around the heat detection wire 2 will vary accordingly, and the current loss (difficulty in flowing) will differ for each electric wire 3. If the current loss differs for each electric wire 3, there is a risk that the efficiency of the non-contact power supply will decrease. Therefore, in this embodiment, in order to make the external shape of the heat detection wire 2 arranged at the center of the cable closer to a circle, a reinforcing layer 25 is formed by wrapping two resin tapes made of polyethylene around the jacket 24 in opposite winding directions. By providing a relatively hard reinforcing layer 25 (for example, harder than the jacket 24) on the outermost circumference of the heat detection wire 2, the outer shape of the heat detection wire 2 can be kept as close to a circular shape as possible, and the cross-sectional shape of the plurality of electric wires 3 can be made uniform (the variation in the outer shape of the plurality of electric wires 3 can be reduced). In other words, the outer shape of the heat detection wire 2 arranged at the center of the cable should be such that the pressing force generated between the heat detection wire 2 and each of the electric wires 3 arranged around the heat detection wire 2 is approximately uniform. In a state in which the electric wires 3 are arranged around the heat detection wire 2 arranged at the center of the cable and the sheath 4 is provided, the heat detection wire 2 is pressed down by the electric wires 3, and therefore the outer shape of the heat detection wire 2 is actually non-circular due to the influence of the pressing force generated between the heat detection wire 2 and each of the plurality of electric wires 3. In this embodiment, the heat detection wire 2 is pressed down by six electric wires 3, and the outer shape of the heat detection wire 2 is approximately hexagonal (see FIG. 2).

[0045] (Aggregation 6) A plurality of electric wires 3 are twisted in a spiral shape around the outer periphery of the heat detection wire 2. Hereinafter, the plurality of electric wires 3 twisted around the heat detection wire 2 will be referred to as an assembly 6.

[0046] When the number of electric wires 3 used in the assembly 6 is one to three, the multi-core cable 1 is less likely to deform due to an external force. Therefore, the number of electric wires 3 used in the assembly 6 of the multi-core cable 1 is set to four or more. In this embodiment, the number of electric wires 3 used in the assembly 6 is set to six, which is the number that can minimize the outer diameter and the total conductor resistance of all the electric wires 3. In the assembly 6, the electric wires 3 adjacent to each other in the cable circumferential direction are in surface contact with each other at the electric wire contact portion 3b. Moreover, the electric wires 3 are in surface contact with the heat detection wire 2 at the heat detection wire contact portion 3a.

[0047] The twisting direction of the assembly 6 is preferably opposite to the twisting direction of the twisted pair wires 22 in the heat detection wire 2. By making the twisting direction of the assembly 6 and the twisted pair wires 22 opposite to each other, the twisting of the electric wires 3 is less likely to loosen, and it is possible to maintain the heat detection wire 2 in a tightened state by the electric wires 3. As a result, when the temperature inside the cable rises, the first conductors 211 are more likely to come into contact with each other due to the tightening of the electric wires 3, and it is possible to improve the detection sensitivity. The twisting direction of the assembly 6 is the direction in which the electric wires 3 rotate from the other end side to the one end side when the assembly 6 is viewed from one end side. The twisting direction of the twisted pair wires 22 is the direction in which the heat detection electric wires 21 rotate from the other end side to the one end side when the twisted pair wires 22 are viewed from one end side.

[0048] In this embodiment, each electric wire 3 constituting the assembly 6 is provided so that the outer periphery 3c thereof is in surface contact with the inner periphery of the sheath 4, and no tape for holding down the assembly 6 is wound around the assembly 6. This is because if tape is wound around the assembly 6, the tape may serve to restrict the movement of the electric wires 3, which may reduce the workability when inserting the multi-core cable 1 into the groove 11. If it is necessary to hold the electric wires 3 in a twisted state for manufacturing reasons, thread (such as resin thread or cotton thread) may be wound helically around the assembly 6.

[0049] A thread-like intervening material may be disposed between the heat detection wire 2 and the electric wires 3, and between the electric wires 3 and the sheath 4. In order to prevent the intervening material from burning due to a rise in temperature inside the cable, it is preferable to use a material with high heat resistance (at least a heat-resistant temperature of 100°C or higher). By having the intervening material, the overall outer shape of the multi-core cable 1 can be made closer to a circular shape, and handling can be improved. In this embodiment, no thread-like intervening material is disposed between the heat detection wire 2 and the electric wires 3, and between the electric wires 3 and the sheath 4. This is to prevent the intervening material from burning due to a rise in temperature, and to ensure a space (i.e., an air layer 5) in which the electric wires 3 can move in the circumferential direction or the outer diameter direction of the heat detection wire 2 when an external force is applied to the multi-core cable 1.

[0050] (Sheath 4) 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-solid extrusion molding (so-called tube extrusion molding). The sheath 4 is formed in a hollow cylindrical shape having a hollow portion 41 along the longitudinal direction, and the heat detection wire 2 and the electric wires 3 (i.e., the assembly 6) are arranged in this hollow portion 41. This allows the electric wires 3 in the multi-core cable 1 to move relative to each other within the sheath 4.

[0051] As described above, in this embodiment, the tape for holding down the wires is omitted, and each of the wires 3 directly contacts the inner peripheral surface of the sheath 4. In this embodiment, the sheath 4 presses the wires 3 radially inward, and presses the wires 3 against the heat detection wire 2. The contact area between the wires 3 and the sheath 4 (the area of ​​the outer peripheral portion 3c) is larger than the contact area between the wires 3 and the heat detection wire 2 (the area of ​​the heat detection wire contact portion 3a).

[0052] The thickness of the sheath 4 is preferably 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 the insulating performance are reduced, and if the thickness of the sheath 4 is more than 1.0 mm, the diameter of the multi-core cable 1 is increased.

[0053] Furthermore, by forming the sheath 4 by non-solid extrusion molding and reducing the thickness of the sheath 4 to 1.0 mm or less, it is possible to create unevenness on the outer surface of the sheath 4 so that the sheath 4 becomes convex at the position of the electric wire 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 into the groove 11 of the housing 10, and also makes it possible to reduce the contact area between the multi-core cable 1 and the housing 10 (the inner surface of the groove 11), making it easier to insert the multi-core cable 1 into the groove 11. In this embodiment, a sheath 4 made of polyvinyl chloride with a thickness of 0.8 mm was used.

[0054] (Evaluation test of heat detection line 2) A thermal detection wire 2 was fabricated as an example using a single-wire phosphorus bronze (7 mass% to 9 mass% tin, 0.03 mass% to 0.35 mass% phosphorus, the remainder being copper and a small amount of unavoidable impurities) with a diameter of 0.9 mm, a tensile strength of 998.9 MPa, and an elongation of 2.4% as the first conductor 211, and its operation was evaluated. In the evaluation, the lengths of the thermal detection wire 2 were set to 80 m, 100 m, and 400 m, and each thermal detection wire 2 was introduced into a thermostatic chamber, and the time until the first conductors 211 were short-circuited was measured. The temperatures in the thermostatic chamber were set to 80° C., 100° C., 120° C., and 140° C., and tests were performed for each. Table 1 shows the measurement results of the thermal detection wire 2 of the example.

[0055] [Table 1]

[0056] As shown in Table 1, the thermal detection wire 2 of the embodiment did not operate for 2 hours at 80°C regardless of the length, but operated within a few minutes (approximately within 3 minutes) at 100°C or higher, confirming that good operation was obtained.

[0057] (Functions and Effects of the Embodiments) As described above, the multi-core cable 1 of this embodiment has a built-in heat detection wire 2, and the second conductor 31 has a cross-sectional shape perpendicular to the longitudinal direction of the cable such that its width along the circumferential direction gradually increases from the radial inner side to the radial outer side.

[0058] The incorporation of the heat detection wire 2 makes it possible to accurately detect a temperature rise in the multi-core cable 1 laid in the housing 10. In addition, by making the cross-sectional shape of the second conductor 31 perpendicular to the cable longitudinal direction gradually wider from the radially inner side to the radially outer side, it is possible to ensure a large cross-sectional area of ​​the second conductor 31 in the limited space inside the sheath 4, and also to increase the cross-sectional area of ​​the second conductor 31 located in the outer periphery where the current is concentrated, thereby making it possible to suppress a decrease in the efficiency of contactless power supply.

[0059] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiment will be described by using the reference numerals and the like in the embodiment. However, the reference numerals and the like in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiment.

[0060] [1] A multi-core cable (1), comprising: a heat detection wire (2) including a twisted pair (22) formed by twisting together a pair of heat detection wires (21) having a first conductor (211) and a first insulator (212) covering the periphery of the first conductor (211); a plurality of electric wires (3) having a second conductor (31) and a second insulator (32) covering the periphery of the second conductor (31), the plurality of electric wires (3) being twisted in a spiral shape around the heat detection wire (2); and a sheath (4) collectively covering the heat detection wire (2) and the plurality of electric wires (3), wherein the melting point of the first insulator (212) is lower than the melting point of the second insulator (32), and the second conductor (31) has a cross-sectional shape perpendicular to the longitudinal direction of the cable such that the width along the circumferential direction gradually increases from the radially inner side to the radially outer side.

[0061] [2] The multi-core cable (1) described in [1], wherein at least one or more of the electric wires (3) are in surface contact with the outer surface of the heat detection wire (2).

[0062] [3] The multi-core cable (1) according to [1] or [2], wherein the electric wires (3) adjacent to each other in the circumferential direction are in surface contact with each other.

[0063] [4] The multi-core cable (1) according to any one of [1] to [3], wherein, in a cross-sectional view perpendicular to the longitudinal direction of the cable, a portion of the outer surface of the second insulator (32) of the plurality of electric wires (3) is formed into a shape that conforms to the inner surface of the sheath (4).

[0064] [5] The heat detection wire (2) has a jacket (24) that covers the twisted pair wires (22) and a reinforcing layer (25) that covers the jacket (24), and the reinforcing layer (25) is a tape layer formed by spirally winding a resin tape around the jacket (24). The multi-core cable (1) described in any one of [1] to [4].

[0065] [6] The multi-core cable (1) according to any one of [1] to [5], wherein the twisted pair wires (22) are covered with a jacket (24), the jacket (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.

[0066] [7] The multi-core cable (1) according to any one of [1] to [6], wherein the first conductor (211) is made of a non-magnetic copper alloy having a tensile strength of 900 MPa or more.

[0067] [8] The multi-core cable (1) according to any one of [1] to [7], wherein when the first insulator (211) softens or melts at a predetermined temperature, the first conductors (211) of the pair of heat detection wires (2) move toward the center of the twisted pair wire (22) due to a force that causes the first conductors (211) to approach each other, and the first conductors (211) come into contact with each other.

[0068] [9] The multi-core cable (1) described in [8], wherein the melting point of the first insulator (211) is greater than 80°C and less than 100°C, and the short circuit does not occur in an environment of 80°C, but occurs within 5 minutes in an environment of 100°C.

[0069]

[10] The multi-core cable (1) according to any one of [1] to [9], wherein the first conductor (211) is made of phosphor bronze containing 7 mass% or more and 9 mass% or less of tin and 0.03 mass% or more and 0.35 mass% or less of phosphorus.

[0070] Although the embodiment of the present invention has been described above, the invention according to the claims is not limited to the embodiment described above. It should be noted that not all of the combinations of features described in the embodiment are essential to the means for solving the problems of the invention. The present invention can be modified appropriately without departing from the spirit of the invention. [Explanation of symbols]

[0071] 1...Multi-core cable 2...Heat detection wire 21...Heat detection wire 211…First conductor 212…First insulator 22...Twisted pair wire 23…Pressing tape 24…Jacket 3…Electric wire 31…Second conductor 32…Second insulator 4…Sheath

Claims

1. A multi-core cable having a detection wire capable of detecting a temperature rise in the cable, A number of electric wires are twisted around the center of the cable in a circumferential direction while being in contact with each other. A sheath is provided to cover the plurality of electric wires, The plurality of electric wires each include a stranded conductor formed by stranding a plurality of wires together, and an insulator covering the periphery of the stranded conductor, The plurality of wires have an outer diameter of 0.15 mm or more and 0.32 mm or less, The stranded conductor has a conductor cross-sectional area of ​​7 mm ２ More than 8mm ２ is as follows: The insulator has a thickness that is equal to or greater than 1 / 2 times and equal to or less than the outer diameter of the plurality of wires. Multicore cable.

2. The outer surfaces of the insulators of the electric wires adjacent to each other in the circumferential direction of the cable are in surface contact with each other.

2. The multi-conductor cable of claim 1.

3. In a cross-sectional view perpendicular to the cable longitudinal direction, the outer surface of the insulator that contacts the inner surface of the sheath has a shape that conforms to the inner surface of the sheath.

3. A multi-core cable according to claim 1 or 2.

4. The insulator is made of tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polytetrafluoroethylene, vinylidene prefluoride, polyimide, or polyether ether ketone. A multi-core cable according to any one of claims 1 to 3.

5. The stranded conductor has a cross-sectional shape perpendicular to the cable longitudinal direction, the cross-sectional shape being such that the width along the cable circumferential direction gradually increases from the inside to the outside in the cable radial direction. A multi-core cable according to any one of claims 1 to 4.

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