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 of the present invention comprises 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 being 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 the outer ends of the rib portions, the inner annular portion, the rib portions, and the outer annular portion forming flow paths the same number as the number of rib portions, the heat-resistant resin layer being formed by overlapping windings of heat-resistant resin tape, and a coolant being circulated through the flow paths to suppress temperature rise during current flow.

[0008] According to this configuration, by providing a flow path for cooling in the sheath of the power cable, it is possible to sufficiently secure a cross-sectional area required for cooling the conductor heat generated during current flow. Furthermore, since the heat-resistant resin layer covering the conductor suppresses heat conduction to the sheath, it is possible to prevent the sheath from melting due to heat. Since the heat-resistant resin layer is formed by overlapping and winding the heat-resistant resin tape, it is easy to manufacture the heat-resistant resin layer. Furthermore, by overlapping and winding the heat-resistant resin tape, it is possible to make a thin tape that is easy to wrap around the conductor, while forming an air layer between the heat-resistant layers of the heat-resistant resin tape, so that it is possible to expect further improvement in heat resistance performance. Therefore, it is possible to provide a cooling structure that can quickly cool the conductor heat generated 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 preferably has a first layer in contact with the conductor made of at least one of polyimide, polyamideimide, and polyamide, which has a heat-resistant temperature of more than 200° C. and can sufficiently withstand the heat generated by the conductor due to an overcurrent.

[0010] The heat-resistant resin layer preferably has an outer layer, which is outer than the first layer, made of polyphenylene sulfide or liquid crystal polymer. The heat energy of the conductor heat is absorbed most by the first layer of the heat-resistant resin layer, which is in contact with the conductor. In other words, the heat-resistant resin layer has a tendency to have a lower heat temperature toward the outermost layer. By providing the first layer of the heat-resistant resin layer with a single winding of polyimide or the like, which has the highest heat resistance, and providing the second and third outer layers, etc., with multiple windings of polyphenylene sulfide or the like, which has high heat resistance and low material costs, it is possible to reduce material costs while maintaining heat resistance against conductor heat.

[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 formed by overlapping and winding a heat-resistant resin tape. By providing the heat-resistant resin layer 3 between the conductor 2 and the inner annular portion 4a, the heat conduction from the conductor 2 to the jacket portion 4 can be suppressed, and the thermal melting of the jacket portion 4 can be prevented. The heat-resistant resin layer 3 is preferably composed of both the first layer 3a in contact with the conductor 2 and the outer layer 3b provided on the outside of the first layer 3a. The first layer 3a preferably has a heat-resistant temperature of 200°C or higher. The first layer 3a may be a single winding, a double winding, or a multiple winding. By winding the first layer 3a in a single winding, the material cost can be reduced to the lowest. The outer layer 3b covering the first layer 3a preferably has a heat-resistant temperature of 160°C or higher. The outer layer 3b may be a single winding, a double winding, or a multiple winding. By winding the outer layer 3b in a single winding, the material cost can be reduced to the highest. By making the number of turns of the first layer 3a smaller than the number of turns of the outer layer 3b, it is possible to reduce material costs while improving heat resistance. In particular, by making the first layer 3a a single-wound and the outer layer 3b a single-wound, it is possible to reduce material costs the most while improving heat resistance.

[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 2 The 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 overlapping and winding heat-resistant resin tapes. The first layer 3a of the heat-resistant resin layer 3 is made of one or more of polyimide, polyamideimide, and polyamide. These heat-resistant resins have a heat-resistant temperature of over 200°C and can fully withstand the heat generated by the conductor 2 due to an overcurrent. As an example, the thickness of the first layer 3a is 0.02 to 0.05 mm. The first layer 3a is wound in a second direction opposite to the first direction, which is the twist direction of the conductor 2. This can prevent wrinkles from occurring in the first layer 3a.

[0025] In the heat-resistant resin layer 3, the outer layer 3b outside the first layer 3a is made of polyphenylene sulfide or liquid crystal polymer. These heat-resistant resins have a heat-resistant temperature of more than 160°C and can fully withstand the heat temperature of the first layer 3a due to heat generation from the conductor 2. As an example, the thickness of one layer of the outer layer 3b is 0.05 to 0.2 mm. The outer layer 3b is wound in a first direction opposite to the second direction in which the first layer 3a is wound. This makes it possible to prevent wrinkles from occurring in the outer layer 3b. As an example, the radial thickness of the heat-resistant resin layer 3 is 0.2 to 1.0 mm.

[0026] According to the manufacturing method of this embodiment, it is easy to manufacture the heat-resistant resin layer 3. Moreover, by overlapping and winding the heat-resistant resin tape, a thin tape that is easy to wind around the conductor 2 is obtained, and an air layer is formed between the heat-resistant layers of the heat-resistant resin tape, so that further improvement in heat resistance can be expected.

[0027] [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.

[0028] [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.

[0029] (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 formed by Z-twisting 12 strands of strands to form a first strand, Z-twisting 6 of the first strand to form a second strand, Z-twisting 5 of the second strand to form a third strand, and then S-twisting 7 of the third strand. The heat-resistant resin layer 3 is formed by wrapping a heat-resistant resin tape of 0.05 mm thick and 30 mm wide, made of polyimide, in a single layer with a wrap ratio of 1 / 4, and wrapping a heat-resistant resin tape of 0.1 mm thick and 30 mm wide, made of polyphenylene sulfide, in a double layer with a wrap ratio of 1 / 4, on the outer side of the first layer 3a. The thickness of the heat-resistant resin layer 3 is 0.35 mm. The outer jacket 4 is made of cross-linked polyethylene resin. The outer sheath 4 has an inner annular portion 4a with a radial thickness of 0.8 mm, a rib portion 4b with a circumferential thickness of 1.4 mm, and an outer annular portion 4c with a radial thickness of 1.2 mm. The outer sheath 4 has six flow paths 5. The power cable of the embodiment has an outer diameter of 16.7 mm and a total length of 3.3 m.

[0030] 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.

[0031] 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.

[0032] (Reference example) The reference example does not have a heat-resistant resin layer 3. The conductor 2 and the jacket 4 in the sample of the reference example are the same as those in the example. The power cable of the reference example 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 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.

[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 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.

[0035] 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]

[0036] 1 Power cable 2 strands 3 Heat-resistant resin layer, 3a 1st layer, 3b outer 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; The heat-resistant resin layer is formed by overlapping and winding a heat-resistant resin tape, 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 has a first layer that is in contact with the conductor and is made of at least one of polyimide, polyamideimide, and polyamide.

2. The power cable according to claim 1 .

3. The heat-resistant resin layer has an outer layer outside the first layer, the outer layer being made of polyphenylene sulfide or liquid crystal polymer.

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,

Images