Power Cable

Abstract

The object of the present invention is to provide a power cable having a heat-resistant structure capable of withstanding conductor heat caused by transient currents such as inrush currents, while also having a cooling structure capable of quickly cooling the conductor heat. [Solution] A power cable 1 includes a conductor 2, a heat-resistant resin layer 3 that covers the conductor 2, and an outer sheath 4 that insulates the heat-resistant resin layer 3. The outer sheath 4 includes an inner annular portion 4a, three or more rib portions 4b that extend radially from the inner annular portion 4a, and an outer annular portion 4c that is connected to the outer end of the rib portion 4b, and the inner annular portion 4a, rib portions 4b, and outer annular portion 4c form flow paths 5 that are the same in number as the rib portions 4b. The power cable 1 is configured to suppress a temperature rise in the outer sheath 4 when electricity is applied by flowing a refrigerant 7 through the flow paths 5.

Description

[Technical field]

[0001] The present invention relates to a power cable for supplying electric power. [Background technology]

[0002] Conventionally, a power supply cable provided with a cooling pipe has been proposed (Patent Document 1: JP 2018-18748 A). Also, a coaxial cable in which a coolant flows in a gap formed in a hollow core body has been proposed (Patent Document 2: JP 2015-100188 A). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-18748 A [Patent Document 2] JP 2015-100188 A Summary of the Invention [Problem to be solved by the invention]

[0004] The power supply cable described in Patent Document 1 has a cooling tube provided at the center of the power line, so it is not possible to ensure a sufficient cross-sectional area required for cooling the conductor heat generated when current is passed through it. In addition, since the cross section has a non-axisymmetric shape, it is less flexible than the coaxial cable with an axisymmetric shape as in Patent Document 2.

[0005] In order to shorten the time it takes to supply power to an electric vehicle, it is necessary to increase the amount of power flowing through the conductor. However, increasing the amount of power increases the amount of heat generated by the conductor, and if the heat generated by the conductor becomes excessive, the outer jacket melts and the insulation performance cannot be maintained. For example, a transient current such as an inrush current can cause a temporary increase in the heat generated by the conductor, exceeding the heat resistance temperature of the hollow core body.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide a power cable having a heat-resistant structure that can withstand conductor heat caused by transient currents such as inrush currents, while also having a cooling structure that can quickly cool the conductor heat. [Means for solving the problem]

[0007] The power cable according to the present invention includes a conductor, a heat-resistant resin layer covering the conductor, and an outer sheath providing an insulating coating for the heat-resistant resin layer. The outer sheath is made of a thermoplastic resin having an integral structure including an inner annular portion, three or more rib portions extending radially from the inner annular portion, and an outer annular portion connected to outer ends of the rib portions, and the inner annular portion, the rib portions, and the outer annular portion form flow paths that are the same in number as the rib portions. The power cable is characterized in that it is configured to suppress temperature rise during current flow by flowing a coolant through the flow paths.

[0008] According to this configuration, by providing a cooling flow path in the sheath of the power cable, it is possible to secure a sufficient cross-sectional area required for cooling the conductor heat generated when electricity is passed through it. Furthermore, since the heat-resistant resin layer covering the conductor suppresses the heat conduction to the sheath, it is possible to prevent the sheath from melting. Therefore, it is possible to provide a cooling structure that can quickly cool the conductor heat while providing a heat-resistant structure that can withstand the conductor heat generated by transient currents such as inrush currents.

[0009] The heat-resistant resin layer is extrusion molded, and the thickness of the heat-resistant resin layer is preferably 0.4 to 1.0 mm. A heat-resistant resin layer of uniform thickness is formed by extrusion molding. By making the radial thickness of the heat-resistant resin layer 0.4 mm or more, moldability is improved and heat resistance performance can be ensured. By making the radial thickness of the heat-resistant resin layer 1.0 mm or less, the power cable can be made thinner and material costs can be reduced.

[0010] The heat-resistant resin layer is preferably made of polyaryletherketone (PAEK), polyphenylene sulfide (PPS), polyamideimide (PAI), polyimide (PI), or polybenzimidazole (PBI). Alternatively, the heat-resistant resin layer is preferably made of fluororesin. The heat-resistant resin layer is preferably made of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), or chlorotrifluoroethylene-ethylene copolymer (ECTFE). These resins all have a heat-resistant temperature of over 150°C, so they can withstand conductor heating caused by overcurrent. In particular, PAEK, PPS, PAI, PI, PBI, PTFE, PFA, and FEP have a heat-resistant temperature of over 200°C, so they can fully withstand conductor heating in higher temperature ranges.

[0011] According to this configuration, while having excellent flexibility, it can easily comply with a power supply method with a current of 300 A or more, a power supply method with a power of 3000 VA, and known charging standards such as CHAdeMO and SAE. As an example, the power cable according to the present invention constitutes a power supply line from a power supply unit to a battery in an electric vehicle. Effect of the Invention

[0012] According to the present invention, it is possible to realize a power cable having a heat-resistant structure capable of withstanding conductor heat caused by transient currents such as inrush currents, while also having a cooling structure capable of quickly cooling the conductor heat. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a schematic example of a power cable according to the present embodiment. [Diagram 2] FIG. 2 is a schematic structural diagram illustrating the example of the power cable of FIG. [Diagram 3]FIG. 3 is a configuration diagram that illustrates an application example of the power cable according to this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 3 as an example, a power cable 1 according to this embodiment constitutes a power supply line from a power supply unit 51a to a battery 51b in an electric vehicle 51. Connectors for connection to the outside are attached to both ends of the power cable 1. A coolant flows through the cable via the connectors. In all the drawings for explaining the embodiment, members having the same functions are given the same reference numerals, and repeated explanations of such members may be omitted.

[0015] [Power cable] As shown in FIG. 1, the power cable 1 of this embodiment includes a conductor 2, a heat-resistant resin layer 3 that insulates the conductor 2, and an outer sheath 4 that insulates the heat-resistant resin layer 3. The outer sheath 4 is made of a thermoplastic resin having an integral structure including an inner annular portion 4a, three or more rib portions 4b that extend radially from the inner annular portion 4a, and an outer annular portion 4c that is connected to the outer end of the rib portion 4b. The number of flow paths 5 surrounded by the inner annular portion 4a, the rib portion 4b, and the outer annular portion 4c is the same as the number of the rib portions 4b. In order to achieve both heat dissipation efficiency and mechanical strength, the number of the rib portions 4b is set to 3 to 9. By setting the number of the rib portions 4b to 3 or more, the mechanical strength of the outer sheath 4 can be sufficiently ensured. By setting the number of the rib portions 4b to 9 or less, the cross-sectional area of ​​the flow path 5 required for cooling by flowing the refrigerant can be sufficiently ensured. More preferably, the number of the rib portions 4b is set to 5 to 7. That is, it is preferable that the number of the flow paths 5 is set to 5 to 7.

[0016] The heat-resistant resin layer 3 is preferably made of polyaryletherketone (PAEK), polyphenylene sulfide (PPS), polyamideimide (PAI), polyimide (PI), or polybenzimidazole (PBI). Alternatively, the heat-resistant resin layer 3 is preferably made of fluororesin. By providing the heat-resistant resin layer 3 between the conductor 2 and the inner annular portion 4a, it is possible to suppress the thermal conduction from the conductor 2 to the jacket 4 and prevent the jacket 4 from melting due to heat. Furthermore, the jacket 4 can be made of a general-purpose resin molded product with excellent moldability, thereby reducing material costs.

[0017] Thermoplastic resins such as olefin resins and fluororesins can be used for the outer cover 4. Olefin resins such as polyethylene and polypropylene are preferable because they can reduce material costs. Cross-linked polyethylene is particularly preferable because it has a heat resistance of 120°C.

[0018] As an example, the outer cover 4 has an inner annular portion 4a with a radial thickness of 0.6 to 2.4 mm, an outer annular portion 4c with a radial thickness of 0.6 to 2.4 mm, and a rib portion 4b with a circumferential thickness of 0.7 to 2.1 mm. This configuration allows the outer cover 4 to have a small diameter, robustness, and excellent flexibility. However, the configuration is not limited to the above.

[0019] As shown in FIG. 2, the power cable 1 of this embodiment is configured to suppress a temperature rise of the jacket portion 4 during energization by flowing the refrigerant 7 through the flow path 5. As an example, the refrigerant 7 is an antifreeze liquid, an inert liquid, or water. As an example, the cooling liquid used for the vehicle-mounted battery 51b is divided to become the refrigerant 7. The refrigerant 7 is then taken in from one end of the power cable 1, made to flow, and discharged from the other end of the power cable 1 to return to the cooling device used for the vehicle-mounted battery 51b. This allows the power cable 1 to be cooled. The arrows in FIG. 2 indicate the direction in which the refrigerant 7 travels. As another example, the refrigerant 7 may be air or an inert gas. As an example, the refrigerant 7 having the same components as the outside air is taken in from one end of the power cable 1, made to flow, and discharged to the outside from the other end of the power cable 1.

[0020] The conductor 2 may be a solid wire. When the conductor 2 is a solid wire, it is a single wire in which an insulating coating such as an oxide coating is formed on the outer periphery of a metal wire made of copper, copper alloy, aluminum, or aluminum alloy. The conductor 2 may be a stranded wire. When the conductor 2 is a stranded wire, it is an assembly of element wires in which an insulating coating such as an oxide coating is formed on the outer periphery of a metal wire made of copper, copper alloy, aluminum, or aluminum alloy. As an example, the conductor 2 has a composite stranded structure having a first stranded wire made of stranded element wires, a second stranded wire made of stranded first strands, and a third stranded wire made of stranded second strands. The insulating coating is preferably made of a material that does not interfere with soldering. As an example, the insulating coating is made of polyurethane, polyester, or the like.

[0021] As an example, the conductor 2 is rope-twisted. Rope twist is a twist structure in which the direction of the final (n+1)th twist in a stranded wire is opposite to the direction of the first twist through the nth twist. Here, n is a natural number equal to or greater than 2. Preferably, n is 2 or 3. Rope twist provides excellent shape stability.

[0022] As an example, the conductor 2 has a plurality of wires twisted in a Z-shape to form a first stranded wire, a plurality of first stranded wires twisted in a Z-shape to form a second stranded wire, and a plurality of second stranded wires twisted in an S-shape to form a third stranded wire. As another example, a plurality of wires twisted in a Z-shape to form a first stranded wire, a plurality of first stranded wires twisted in a Z-shape to form a second stranded wire, a plurality of second stranded wires twisted in a Z-shape to form a third stranded wire, and a plurality of third stranded wires twisted in an S-shape to form a fourth stranded wire. As another example, a plurality of wires twisted in an S-shape to form a first stranded wire, a plurality of first stranded wires twisted in an S-shape to form a second stranded wire, and a plurality of second stranded wires twisted in a Z-shape to form a third stranded wire. As another example, a plurality of wires twisted in an S-shape to form a first stranded wire, a plurality of first stranded wires twisted in an S-shape to form a second stranded wire, a plurality of second stranded wires twisted in an S-shape to form a third stranded wire, and a plurality of third stranded wires twisted in a Z-shape to form a fourth stranded wire. Here, Z twist is synonymous with left twist and S twist is synonymous with right twist.

[0023] As an example, the conductor 2 is a wire made of a metal wire made of copper or a copper alloy and an insulating coating made of polyurethane. The total cross-sectional area of ​​the conductor is 20 to 120 mm 2The insulating coating has a radial thickness of 0.006 to 0.018 mm.

[0024] [Method of manufacturing heat-resistant resin layer] The heat-resistant resin layer 3 is formed by extruding molten resin using a ring-shaped die and slowly cooling and solidifying it. This extrusion molding results in the heat-resistant resin layer 3 being integrally formed around the conductor 2. The manufacturing method of this embodiment makes it possible to obtain a heat-resistant resin layer 3 that is thin in diameter, robust, and highly flexible.

[0025] [Manufacturing method of the outer jacket] The outer jacket 4 is manufactured using a dedicated die. The dedicated die has a central hole, an inner annular hole formed adjacent to the outer edge of the central hole so as to surround the central hole, six or more predetermined-shape holes extending radially from the outer periphery of the inner annular hole and wider than the inner annular hole, and an outer annular hole connecting the outer ends of the predetermined-shape holes and wider than the inner annular hole. Using the dedicated die, molten resin is extruded from the inner annular hole, the predetermined-shape hole, and the outer annular hole, and is gradually cooled and solidified. By forming the outer jacket 4 by this extrusion molding, the inner annular portion 4a, the rib portion 4b extending radially from the inner annular portion 4a, and the outer annular portion 4c connecting the outer ends of the rib portion 4b are integrally formed with a thermoplastic resin around the heat-resistant resin layer 3. Furthermore, a flow path 5 is formed that is continuous in the longitudinal direction and is surrounded by the inner annular portion 4a, the rib portion 4b, and the outer annular portion 4c. According to the manufacturing method of this embodiment, a power cable 1 that is small in diameter, robust, and highly flexible can be obtained.

[0026] [Air cooling test] Next, an air-cooling test was performed on a sample to confirm the cooling capacity of the above-mentioned power cable 1. The test standard was JIS C2805:2010.

[0027] (Example) The conductor 2 in the sample of the embodiment is a stranded wire using a second-class polyurethane copper wire with an outer diameter of 0.12 mm. The stranded wire as the conductor 2 is a first stranded wire made by Z-twisting 12 strands, a second stranded wire made by Z-twisting 6 strands of the first stranded wire, a third stranded wire made by Z-twisting 5 strands of the second stranded wire, and then a third stranded wire made by S-twisting 7 strands. The heat-resistant resin layer 3 is extrusion-molded from PFA. The radial thickness of the heat-resistant resin layer 3 is 0.4 mm. The jacket 4 is made of cross-linked polyethylene resin. The jacket 4 has a radial thickness of 0.8 mm at the inner annular portion 4a, a circumferential thickness of 1.4 mm at the rib portion 4b, and a radial thickness of 1.2 mm at the outer annular portion 4c. The jacket 4 has six flow paths 5 formed therein. The power cable 1 of the embodiment has an outer diameter of 16.8 mm and a total length of 3.3 m.

[0028] In the first air-cooling test, an air coupler was attached to one end of the sample, the other end of the sample was opened, a direct current of 50A was continuously applied to the conductor 2, and the surface temperature of each part of the sample was measured by a non-contact thermometer. As a result of the continuous application of electricity, the surface temperature of the conductor 2 became 154°C, and the surface temperature of the outer jacket 4 became 118°C. After that, air at room temperature was forced into the one end of the sample as the refrigerant 7 at a flow rate of 70 liters per minute, and the air was released to the outside from the other end of the sample. As a result of measuring the temperature after 10 minutes of continuous air-cooling by a non-contact thermometer, the surface temperature of the conductor 2 became 100°C, and the surface temperature of the outer jacket 4 became 42°C. Therefore, it was confirmed that in the example, the surface temperature of the conductor 2 was cooled by 54°C, and the surface temperature of the outer jacket 4 was cooled by 76°C by flowing the refrigerant 7.

[0029] In the second air-cooling test, an air coupler was attached to one end of the sample, the other end of the sample was opened, and a direct current of 70A was continuously applied to the conductor 2, and the surface temperature of each part of the sample was measured by a non-contact thermometer. As a result of the continuous application of current, the surface temperature of the conductor 2 reached 164°C, and the surface temperature of the outer jacket 4 reached 128°C. After that, air at room temperature was forced into the one end of the sample as the refrigerant 7 at a flow rate of 70 liters per minute, and the air was released to the outside from the other end of the sample. As a result of measuring the temperature after 10 minutes of continuous air-cooling by a non-contact thermometer, the surface temperature of the conductor 2 reached 90°C, and the surface temperature of the outer jacket 4 reached 50°C. Thus, it was confirmed that in the example, the surface temperature of the conductor 2 was cooled by 74°C, and the surface temperature of the outer jacket 4 was cooled by 78°C by flowing the refrigerant 7.

[0030] (Reference example) The reference example does not have a heat-resistant resin layer 3. The conductor 2 and the outer jacket 4 in the sample of the reference example are the same as those in the examples. The outer diameter of the sample of the reference example is 16.0 The reference example does not have a heat-resistant resin layer 3. The conductor 2 and the outer jacket 4 in the sample of the reference example are the same as those in the examples. The power cable of the reference example has an outer diameter of 16.0 mm and a total length of 3.3 m.

[0031] In the first air-cooling test, an air coupler was attached to one end of the sample, the other end of the sample was opened, a direct current of 50A was continuously applied to the conductor 2, and the surface temperature of each part of the sample was measured by a non-contact thermometer. As a result of the continuous application of current, the surface temperature of the conductor 2 reached 154°C, and the surface temperature of the outer jacket 4 reached 121°C. After that, air at room temperature was forced into the one end of the sample as the refrigerant 7 at a flow rate of 70 liters per minute, and the air was released to the outside from the other end of the sample. The temperature was measured by a non-contact thermometer after 10 minutes of continuous air cooling, and the surface temperature of the conductor 2 reached 105°C, and the surface temperature of the outer jacket 4 reached 49°C. Therefore, it was confirmed that in the reference example, the surface temperature of the conductor 2 was cooled by 49°C, and the surface temperature of the outer jacket 4 was cooled by 72°C by flowing the refrigerant 7.

[0032] In the second air-cooling test, an air coupler was attached to one end of the sample, the other end of the sample was opened, and a direct current of 70 A was continuously applied to the conductor 2, and the surface temperature of each part of the sample was measured with a non-contact thermometer. As a result of the continuous application of current, the surface temperature of the conductor 2 reached 164°C, and the surface temperature of the outer jacket 4 reached 131°C. After that, room temperature air was forced into the one end of the sample as the refrigerant 7 at a flow rate of 70 liters per minute, and the air was released to the outside from the other end of the sample. The temperature was measured with a non-contact thermometer after 10 minutes of continuous air cooling, and the surface temperature of the conductor 2 reached 94°C, and the surface temperature of the outer jacket 4 reached 52°C. Therefore, it was confirmed that in the reference example, the surface temperature of the conductor 2 was cooled by 70°C, and the surface temperature of the outer jacket 4 was cooled by 79°C by flowing the refrigerant 7.

[0033] As a result of the above-mentioned air-cooling test, it was confirmed that in both the Example and the Reference Example, the temperature rise of the jacket part 4 can be suppressed by flowing the coolant 7 through the flow path 5. Furthermore, it was confirmed that the Example in which the heat-resistant resin layer 3 is provided can further suppress the temperature rise of the jacket part 4 during current flow, compared to the Reference Example in which the heat-resistant resin layer 3 is not provided. [Explanation of symbols]

[0034] 1 Power cable 2 Conductors 3 Heat-resistant resin layer 4: outer covering portion, 4a: inner annular portion, 4b: rib portion, 4c: outer annular portion 5 Flow Path 7. Refrigerants 51 Electric vehicle, 51a Power supply unit, 51b Battery

Claims

1. The cable includes a conductor, a heat-resistant resin layer that covers the conductor, and an outer sheath that insulates the heat-resistant resin layer, the outer covering portion is made of a thermoplastic resin having an integral structure including an inner annular portion, three or more rib portions extending radially from the inner annular portion, and an outer annular portion connected to outer ends of the rib portions, and the inner annular portion, the rib portions, and the outer annular portion form flow paths surrounded by the inner annular portion, the rib portions, and the outer annular portion, the flow paths being equal in number to the number of the rib portions; A configuration in which a coolant flows through the flow path to suppress a rise in temperature when electricity is applied A power cable comprising:

2. The heat-resistant resin layer is extrusion molded, and the thickness of the heat-resistant resin layer is 0.4 to 1.0 mm.

2. The power cable according to claim 1 .

3. The heat-resistant resin layer is made of polyaryletherketone, polyphenylene sulfide, polyamideimide, polyimide, polybenzimidazole, tetrafluoroethylene-perfluoroalkylvinylether copolymer, polytetrafluoroethylene, or tetrafluoroethylene-hexafluoropropylene copolymer.

3. The power cable according to claim 2 .

4. To configure a power supply line from a power supply unit to a battery in an electric vehicle The power cable according to any one of claims 1 to 3,

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