Power Cable

Abstract

An object of the present invention is to provide a power cable having a cooling structure capable of quickly cooling conductor heat caused by transient currents such as inrush currents. [Solution] The power cable 1 includes a twisted wire 2 and an outer sheath 4 that insulates the twisted wire 2. The outer sheath 4 includes an inner annular portion 4a, three or more rib portions 4b extending radially from the inner annular portion 4a, and an outer annular portion 4c connected to the outer end of the rib portion 4b. The inner annular portion 4a, the rib portion 4b, and the outer annular portion 4c form flow passages 5 that are the same in number as the rib portions 4b. The twisted wire 2 is an assembly of wires having an insulating layer formed on the outer periphery of the conductor. The power cable 1 has a gap portion 6 that includes an outer gap portion 6a formed outside the twisted wire 2 and an inner gap portion 6b formed inside the twisted wire 2. The power cable 1 is configured to suppress a temperature rise during current flow by flowing a refrigerant 7 through the flow passages 5 and the gap portion 6.

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 of the present invention comprises a twisted wire and an outer sheath that insulates the twisted wire, the outer sheath including an inner annular portion, three or more rib portions extending radially from the inner annular portion, and an outer annular portion connected to the outer end of the rib portion, the inner annular portion, the rib portions, and the outer annular portion form flow paths that are equal in number to the number of rib portions, the twisted wire is an assembly of wires having an insulating layer formed on the outer periphery of a metal wire, and a void portion is formed in the void portion, the void portion being an outer void portion formed on the outside of the twisted wire and an inner void portion formed on the inside of the twisted wire, and a coolant is caused to flow in the flow paths and the void portion to suppress a temperature rise during current flow.

[0008] According to this configuration, since the flow passage for cooling is provided in the jacket and the gap for cooling is provided inside the inner annular portion, it is possible to secure a sufficient cross-sectional area required for cooling the conductor heat generated when current is passed through it, and it is possible to directly cool the stranded wire by the coolant coming into contact with it and absorbing heat, thus significantly improving the cooling efficiency.

[0009] The porosity of the gap is preferably 27 to 35%. The porosity is expressed as a percentage of the cross-sectional area of ​​the gap with respect to the inside cross-sectional area of ​​the inner annular portion. The porosity can be calculated using a gap cross-sectional area obtained by adding up the outside gap cross-sectional area formed by the stranded wire and the inner annular portion and the inside gap cross-sectional area formed inside the stranded wire. By setting the porosity to 27% or more, the stranded wire can be sufficiently cooled. By setting the porosity to 35% or less, the power supplied to the stranded wire can be sufficiently secured.

[0010] The stranded wire is preferably a rope stranded wire, which provides excellent shape stability. In addition, the gap is formed in a spiral shape, so that the surface area and volume of the gap for the flow of the refrigerant can be sufficiently secured.

[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 cooling structure capable of quickly cooling conductor heat caused by transient current such as inrush current. [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. 3A is a diagram showing the arrangement of voids when the final strand of the twisted wire is 3-ply, Fig. 3B is a diagram showing the arrangement of voids when the final strand of the twisted wire is 4-ply, Fig. 3C is a diagram showing the arrangement of voids when the final strand of the twisted wire is 5-ply, and Fig. 3D is a diagram showing the arrangement of voids when the final strand of the twisted wire is 6-ply. [Figure 4] FIG. 4 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. 4 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 twisted wire 2 and an outer sheath 4 that insulates the twisted wire 2. The outer sheath 4 is made of a thermoplastic resin that is integral with 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 inner annular portion 4a, the rib portion 4b, and the outer annular portion 4c form flow paths 5 that are the same in number as 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] 1, the power cable 1 has six rib portions 4b extending radially from the inner annular portion 4a, and six flow paths 5 are formed. As described later, the power cable 1 has a gap 6 consisting of a plurality of outer gaps 6a formed by the outer peripheral surface of the composite stranded structure of the stranded wire 2 and the inner peripheral surface of the inner annular portion 4a, and a plurality of inner gaps 6b formed inside the stranded wire 2.

[0017] As shown in FIG. 2, the power cable 1 of this embodiment is configured to suppress a temperature rise during current flow by flowing a refrigerant 7 through the flow path 5 and the gap 6. As an example, the refrigerant 7 is air or an inert gas. This can prevent the weight of the power cable 1 from increasing. As an example, outside air is used as the refrigerant 7. The refrigerant 7 is taken in from one end of the power cable 1, made to flow, and released outside from the other end of the power cable 1. This can easily cool the power cable 1. The arrow in FIG. 2 indicates the direction in which the refrigerant 7 travels. Note that as another configuration, the refrigerant 7 may be an inert liquid or an antifreeze liquid.

[0018] The stranded wire 2 according to this embodiment is formed by twisting together copper or aluminum wires. As an example, the stranded wire 2 is an assembly of wires in which an insulating coating such as an oxide coating is formed on the outer periphery of a metal wire made of copper or a copper alloy. As an example, the stranded wire 2 has a composite twisted structure having a first stranded wire made of twisted wires, a second stranded wire made of twisted first strands, and a third stranded wire made of twisted second strands. The insulating coating in the stranded wire 2 is made of a material that does not interfere with soldering. As an example, the insulating coating in the stranded wire 2 is made of polyurethane, polyester, or the like.

[0019] As an example, the void ratio α of the void portion 6 is 27 to 35%. The void ratio α is expressed as a percentage of the cross-sectional area of ​​the void portion 6 with respect to the inside cross-sectional area of ​​the inner annular portion 4a. Since the outer periphery of the stranded wire 2 is inscribed inside the inner annular portion 4a, the void ratio α can be calculated from the relationship between the two.

[0020] FIG. 3A is a diagram showing a schematic arrangement of the voids 6 when the final strand of the twisted wire 2 is three strands. When the final strand of the twisted wire 2 is three strands, the void ratio α is 35%. FIG. 3B is a diagram showing a schematic arrangement of the voids 6 when the final strand of the twisted wire 2 is four strands. When the final strand of the twisted wire 2 is four strands, the void ratio α is 31%. FIG. 3C is a diagram showing a schematic arrangement of the voids 6 when the final strand of the twisted wire 2 is five strands. When the final strand of the twisted wire 2 is five strands, the void ratio α is 31%. FIG. 3D is a diagram showing a schematic arrangement of the voids 6 when the final strand of the twisted wire 2 is six strands. When the final strand of the twisted wire 2 is six strands, the void ratio α is 33%.

[0021] When the final strand of wire 2 is 7 strands, the void percentage α is 33%. When the final strand of wire 2 is 8 strands, the void percentage α is 27%. When the final strand of wire 2 is 9 strands, the void percentage α is 31%. When the final strand of wire 2 is 10 strands, the void percentage α is 31%. And when the final strand of wire 2 is 11 strands, the void percentage α is 29%.

[0022] In the example of Fig. 2, the stranded wire 2 is a rope strand. A rope strand is a strand structure in which the direction of the final (n+1)th strand in the stranded wire 2 is opposite to the direction of the first to nth strands. Here, n is a natural number equal to or greater than 2. Preferably, n is 2 or 3.

[0023] As an example, a plurality of elemental wires are Z-twisted to form a first stranded wire, a plurality of first stranded wires are Z-twisted to form a second stranded wire, and a plurality of second stranded wires are S-twisted to form a third stranded wire. As another example, a plurality of elemental wires are Z-twisted to form a first stranded wire, a plurality of first stranded wires are Z-twisted to form a second stranded wire, a plurality of second stranded wires are Z-twisted to form a third stranded wire, and a plurality of third stranded wires are S-twisted to form a fourth stranded wire. As another example, a plurality of elemental wires are S-twisted to form a first stranded wire, a plurality of first stranded wires are S-twisted to form a second stranded wire, and a plurality of second stranded wires are Z-twisted to form a third stranded wire. As another example, a plurality of elemental wires are S-twisted to form a first stranded wire, a plurality of first stranded wires are S-twisted to form a second stranded wire, a plurality of second stranded wires are S-twisted to form a third stranded wire, and a plurality of third stranded wires are Z-twisted to form a fourth stranded wire. Here, Z twist is synonymous with left twist and S twist is synonymous with right twist.

[0024] As an example, the stranded wire 2 is 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 2 The insulating coating has a radial thickness of 0.006 to 0.018 mm.

[0025] As an example, 3 to 12 strands of wire are S-twisted to form strand 2. As an example, 10 to 20 strands of wire are S-twisted to form the first strand, and 4 to 7 strands of the first strand are S-twisted to form strand 2. As an example, 27 strands of wire are S-twisted to form the first strand, and 7 strands of the first strand are S-twisted to form strand 2. As an example, 30 strands of wire are S-twisted to form the first strand, and 8 strands of the first strand are S-twisted to form strand 2. As an example, 35 strands of wire are S-twisted to form the first strand, and 10 strands of the first strand are S-twisted to form strand 2. As an example, 10 to 35 strands of wire are S-twisted to form the first strand, and 4 to 10 strands of the first strand are S-twisted to form strand 2.

[0026] As an example, six wires are Z-twisted to form the first strand, four wires are Z-twisted to form the second strand, and four wires are S-twisted to form the second strand. As an example, six wires are Z-twisted to form the first strand, four wires are Z-twisted to form the second strand, and five wires are S-twisted to form the second strand. As an example, six wires are Z-twisted to form the first strand, five wires are Z-twisted to form the second strand, and seven wires are S-twisted to form the second strand. As an example, eight wires are Z-twisted to form the first strand, five wires are Z-twisted to form the first strand, and seven wires are S-twisted to form the second strand. As an example, 10 wires are Z-twisted to form the first strand, 5 wires of the first strand are Z-twisted to form the second strand, and 7 wires of the second strand are S-twisted to form strand 2. As an example, 12 wires are Z-twisted to form the first strand, 6 wires of the first strand are Z-twisted to form the second strand, and 10 wires of the second strand are S-twisted to form strand 2. As an example, 6 to 12 wires are Z-twisted to form the first strand, 4 to 6 wires of the first strand are Z-twisted to form the second strand, and 4 to 10 wires of the second strand are S-twisted to form strand 2.

[0027] As an example, six wires are Z-twisted to form the first strand, four of the first strand are Z-twisted to form the second strand, four of the second strand are Z-twisted to form the third strand, and four of the third strand are S-twisted to form strand 2. As an example, seven wires are Z-twisted to form the first strand, six of the first strand are Z-twisted to form the second strand, five of the second strand are Z-twisted to form the third strand, and five of the third strand are S-twisted to form strand 2. As an example, eight wires are Z-twisted to form the first strand, six of the first strand are Z-twisted to form the second strand, five of the second strand are Z-twisted to form the third strand, and seven of the third strand are S-twisted to form strand 2. As an example, 10 wires are Z-twisted to form the first strand, 6 wires are Z-twisted to form the second strand, 5 wires are Z-twisted to form the third strand, and 7 wires are S-twisted to form the third strand. As an example, 12 wires are Z-twisted to form the first strand, 6 wires are Z-twisted to form the second strand, 6 wires are Z-twisted to form the third strand, and 7 wires are S-twisted to form the third strand. As an example, 12 wires are Z-twisted to form the first strand, 7 wires are Z-twisted to form the first strand, 6 wires are Z-twisted to form the second strand, 6 wires are Z-twisted to form the third strand, and 7 wires are S-twisted to form the third strand. As an example, 6 to 12 strands are Z-twisted to form a first stranded wire, 4 to 10 strands of the first stranded wire are Z-twisted to form a second stranded wire, 4 to 6 strands of the second stranded wire are Z-twisted to form a third stranded wire, and 4 to 10 strands of the third stranded wire are S-twisted to form stranded wire 2.

[0028] The outer jacket 4 can be made of an olefin resin such as polyethylene or polypropylene. Cross-linked polyethylene is particularly preferable because it has a heat resistance of 120°C. The outer jacket 4 can be made of a fluororesin such as PTFE, PFA, FEP, PCTFE, ETFE, or ECTFE. These fluororesins have better heat resistance than olefin resins.

[0029] As an example, the outer cover 4 has a radial thickness of 0.6 to 2.4 mm for the inner annular portion 4a, a radial thickness of 0.6 to 2.4 mm for the outer annular portion 4c, and a circumferential thickness of 0.7 to 2.1 mm for the rib portion 4b. 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.

[0030] [Manufacturing method of the outer jacket] The outer jacket 4 is manufactured using a die. The 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 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 twisted wire 2. Furthermore, a flow path 5 continuous in the longitudinal direction is formed by being surrounded by the inner annular portion 4a, the rib portion 4b, and the outer annular portion 4c. Furthermore, an outer void portion 6a continuous in the longitudinal direction is formed by being surrounded by the outer circumferential surface of the twisted wire 2 and the inner circumferential surface of the inner annular portion 4a. According to the manufacturing method of this embodiment, it is possible to produce a power cable 1 that is small in diameter, robust, and highly flexible.

[0031] [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.

[0032] (Example) The stranded wire 2 in the sample of the embodiment is a rope stranded wire in which 2520 second-class polyurethane copper wires with an outer diameter of 0.12 mm are stranded. The stranded wire 2 is formed by Z-twisting 12 strands of strands to form a first stranded wire, Z-twisting 6 strands of the first stranded wire to form a second stranded wire, Z-twisting 5 strands of the second stranded wire to form a third stranded wire, and S-twisting 7 strands of the third stranded wire. The stranded wire 2 has a gap portion 6 consisting of a plurality of outer gap portions 6a formed by the outer peripheral surface of the stranded wire 2 and the inner peripheral surface of the inner annular portion 4a, and an inner gap portion 6b formed inside the stranded wire 2, and the void ratio α of the gap portion 6 is 33%. The outer sheath portion 4 is made of cross-linked polyethylene resin. The outer sheath portion 4 has a radial thickness of 0.8 mm at the inner annular portion 4a, a circumferential thickness of the rib portion 4b, and a radial thickness of the outer annular portion 4c of 1.2 mm. The jacket portion 4 has six flow paths 5 formed therein. The power cable 1 of Example 1 has an outer diameter of 16.0 mm and a total length of 3.3 m.

[0033] 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 stranded wire 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 stranded wire 2 reached 154°C, and the surface temperature of the jacket 4 reached 121°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 by a non-contact thermometer after 10 minutes of continuous air cooling. As a result, the surface temperature of the stranded wire 2 reached 95°C, and the surface temperature of the jacket 4 reached 45°C. Thus, it was confirmed that in the example, the surface temperature of the stranded wire 2 was cooled by 59°C, and the surface temperature of the jacket 4 was cooled by 76°C by flowing the refrigerant 7.

[0034] 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 stranded wire 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 stranded wire 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 by a non-contact thermometer after 10 minutes of continuous air cooling. As a result, the surface temperature of the stranded wire 2 reached 85°C, and the surface temperature of the outer jacket 4 reached 47°C. Thus, it was confirmed that in the example, the surface temperature of the stranded wire 2 was cooled by 79°C, and the surface temperature of the outer jacket 4 was cooled by 84°C by flowing the refrigerant 7.

[0035] (Reference example) The sample of the reference example is a bundled conductor made of 2520 second-class polyurethane copper wires with an outer diameter of 0.12 mm. The outer sheath of the reference example is the same as that of the example. The outer diameter and total length of the cable of the reference example are the same as those of the example.

[0036] 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 stranded wire 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 reached 154°C, and the surface temperature of the sheath reached 121°C. After that, room temperature air was forced into 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 10 minutes after the continuous air-cooling. As a result, the surface temperature of the conductor reached 105°C, and the surface temperature of the sheath reached 49°C. Therefore, it was confirmed that in the reference example, the surface temperature of the conductor was cooled by 49°C, and the surface temperature of the sheath was cooled by 72°C by flowing the refrigerant 7.

[0037] 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 stranded wire 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 reached 164°C, and the surface temperature of the sheath reached 131°C. After that, room temperature air was forced into 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 10 minutes after the continuous air-cooling. As a result, the surface temperature of the conductor reached 94°C, and the surface temperature of the sheath reached 52°C. Therefore, it was confirmed that in the reference example, the surface temperature of the conductor was cooled by 70°C, and the surface temperature of the sheath 4 was cooled by 79°C by flowing the refrigerant 7.

[0038] 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 can be suppressed by flowing the coolant 7 through the flow path 5. Furthermore, it was confirmed that the Example can further suppress the temperature rise during current flow, compared to the Reference Example that does not have the void portion 6. [Explanation of symbols]

[0039] 1 Power cable 2 strands 4: outer covering portion, 4a: inner annular portion, 4b: rib portion, 4c: outer annular portion 5 Flow Path 6 Cavity, 6a Outer cavity, 6b Inner cavity 6b 7. Refrigerants 51 Electric vehicle, 51a Power supply unit, 51b Battery α porosity

Claims

1. a twisted wire and an outer covering that insulates the twisted wire, the outer covering including an inner annular portion, three or more rib portions extending radially from the inner annular portion, and an outer annular portion connected to an outer end of the rib portion, the inner annular portion, the rib portions, and the outer annular portion defining flow paths that are the same in number as the rib portions; The stranded wire is an assembly of wires in which an insulating layer is formed on the outer periphery of a metal wire, and a void portion is formed, the void portion being composed of an outer void portion formed on the outer side of the stranded wire and an inner void portion formed on the inner side of the stranded wire, A configuration in which a coolant flows through the flow path and the gap to suppress a temperature rise during energization. A power cable comprising:

2. The porosity of the void portion is 27 to 35%.

2. The power cable according to claim 1 .

3. The stranded wire is a rope strand.

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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