Power cable
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- TOTOKU INC
- Filing Date
- 2025-10-09
- Publication Date
- 2026-07-30
Smart Images
Figure JP2025035759_30072026_PF_FP_ABST
Abstract
Description
Power cable
[0001] The present invention relates to a power cable for power supply.
[0002] Conventionally, a power supply cable provided with a cooling pipe has been proposed (Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-18748). In addition, a coaxial cable in which a refrigerant flows through a void formed in a hollow core body has been proposed (Patent Document 2: Japanese Unexamined Patent Application Publication No. 2015-100188).
[0003] Japanese Unexamined Patent Application Publication No. 2018-18748, Japanese Unexamined Patent Application Publication No. 2015-100188
[0004] In the power supply cable described in Patent Document 1, since the cooling pipe is provided at the center of the power line, it is not possible to sufficiently secure the cross-sectional area required for cooling the conductor heat generation during energization. Further, since the cross-section has a non-axisymmetric shape, it has less flexibility than the coaxial cable having an axisymmetric shape as in Patent Document 2.
[0005] In order to shorten the power supply time to an electric vehicle, it is necessary to increase the amount of electric power flowing through the conductor. On the other hand, when the amount of electric power is increased, conductor heat generation increases, and if the conductor heat generation becomes excessive, there is a problem that the outer covering melts and the insulation performance cannot be maintained. For example, due to an excessive current such as an inrush current, the conductor heat generation may temporarily increase and exceed the heat-resistant temperature of the hollow core body.
[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a power cable having a heat-resistant structure capable of withstanding conductor heat generation caused by an excessive current such as an inrush current and a cooling structure capable of quickly cooling the conductor heat generation.
[0007] The power cable according to the present invention includes a conductor, a heat-resistant resin layer covering the conductor, and an outer covering portion insulatingly covering the heat-resistant resin layer. The outer covering portion is made of a thermoplastic resin having an integral structure of an inner annular portion, three or more rib portions radially extending from the inner annular portion, and an outer annular portion connected to the outer ends of the rib portions, and a flow path surrounded by the inner annular portion, the rib portions, and the outer annular portion is formed in the same number as the rib portions. The power cable is configured to suppress a temperature rise during energization by flowing a refrigerant through the flow path.
[0008] This configuration provides a cooling channel in the outer sheath of the power cable, ensuring sufficient cross-sectional area for cooling the conductor heat generated during energization. Furthermore, the heat-resistant resin layer covering the conductor suppresses heat conduction to the outer sheath, preventing the outer sheath from melting. Thus, it is possible to create a heat-resistant structure that can withstand conductor heat generated by excessive currents such as inrush currents, while also providing a cooling structure that can quickly cool the conductor heat.
[0009] The heat-resistant resin layer is extruded, and its thickness is preferably 0.4 to 1.0 mm. Extrusion molding forms a heat-resistant resin layer of uniform thickness. Making the radial thickness of the heat-resistant resin layer 0.4 mm or more improves moldability and ensures heat resistance. Making the radial thickness of the heat-resistant resin layer 1.0 mm or less allows for smaller diameter power cables and reduces material costs.
[0010] The heat-resistant resin layer is preferably composed of polyaryl ether ketone (PAEK), polyphenylene sulfide (PPS), polyamide-imide (PAI), polyimide (PI), or polybenzimidazole (PBI). Alternatively, the heat-resistant resin layer is preferably composed of a fluororesin. The heat-resistant resin layer is preferably composed of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), or chlorotrifluoroethylene-ethylene copolymer (ECTFE). Since all of these resins have a heat resistance temperature of over 150°C, they can withstand conductor heating due to overcurrent. In particular, PAEK, PPS, PAI, PI, PBI, PTFE, PFA, and FEP have a heat resistance temperature of over 200°C, so they can sufficiently withstand conductor heating in higher temperature ranges.
[0011] This configuration provides excellent flexibility while easily accommodating power supply methods with currents of 300A or more, power supply methods with a power of 3000VA, 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 the power supply unit to the battery in an electric vehicle.
[0012] According to the present invention, a power cable can be realized that has a heat-resistant structure capable of withstanding conductor heat generation caused by excessive currents such as inrush currents, while also having a cooling structure capable of rapidly cooling the conductor heat.
[0013] Figure 1 is a schematic cross-sectional view showing an example of a power cable according to this embodiment. Figure 2 is a schematic structural diagram showing an example of the power cable shown in Figure 1. Figure 3 is a schematic configuration diagram showing an application example of the power cable according to this embodiment.
[0014] Embodiments of the present invention will be described in detail below with reference to the drawings. As an example, the power cable 1 according to this embodiment constitutes a power supply line from the power supply unit 51a to the battery 51b in an electric vehicle 51, as shown in Figure 3. Connectors for external connection are attached to both ends of the power cable 1. The coolant flows through the cable via the connectors. In the diagrams used to explain the embodiments, components having the same function are denoted by the same reference numerals, and repeated explanations may be omitted.
[0015] [Power Cable] As shown in Figure 1, the power cable 1 of this embodiment comprises 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 with an integral structure comprising 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 ends of the rib portions 4b. The number of flow channels 5 surrounded by the inner annular portion 4a, the rib portions 4b, and the outer annular portion 4c is the same as the number of rib portions 4b. In order to achieve both heat dissipation efficiency and mechanical strength, the number of rib portions 4b is set to 3 to 9. By setting the number of rib portions 4b to 3 or more, sufficient mechanical strength of the outer sheath 4 can be ensured. By setting the number of rib portions 4b to 9 or less, sufficient cross-sectional area of the flow channels 5 necessary for cooling by flowing a refrigerant can be ensured. More preferably, the number of rib portions 4b is set to 5 to 7. In other words, it is preferable that the number of flow channels 5 be set to 5 to 7.
[0016] The heat-resistant resin layer 3 is preferably made of polyaryl ether ketone (PAEK), polyphenylene sulfide (PPS), polyamide-imide (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, heat conduction from the conductor 2 to the outer sheath portion 4 can be suppressed, preventing thermal melting of the outer sheath portion 4. Furthermore, the outer sheath portion 4 can be made of a general-purpose resin molded product with excellent moldability, thereby reducing material costs.
[0017] The outer covering portion 4 can be made of thermoplastic resins such as olefin resins or fluororesins. Olefin resins such as polyethylene and polypropylene are preferred because they can reduce material costs. Crosslinked polyethylene is particularly preferred because it has a heat resistance temperature of 120°C.
[0018] As an example, the outer sheath portion 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 for a small diameter, robust, and highly flexible structure. However, the configuration is not limited to the above.
[0019] As shown in Figure 2, the power cable 1 of this embodiment is configured to suppress the temperature rise of the outer sheath 4 when energized by flowing a refrigerant 7 through the flow path 5. For example, the refrigerant 7 is antifreeze, an inert liquid, or water. For example, the coolant used in the vehicle's battery 51b is diverted 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 be returned to the cooling device used in the vehicle's battery 51b. This allows the power cable 1 to be cooled. The arrows in Figure 2 indicate the direction of flow of the refrigerant 7. In addition to the above configuration, the refrigerant 7 may be air or an inert gas. For example, refrigerant 7 with the same components as 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 single wire. When the conductor 2 is a single wire, it is a single wire in which an insulating coating such as an oxide film is formed on the outer circumference of a metal wire made of copper, a copper alloy, or aluminum or an aluminum alloy. The conductor 2 may also be a stranded wire. When the conductor 2 is a stranded wire, it is an assembly of individual wires in which an insulating coating such as an oxide film is formed on the outer circumference of a metal wire made of copper, a copper alloy, or aluminum or an aluminum alloy. As an example, the conductor 2 is a composite stranded structure having a first stranded wire formed by twisting individual wires, a second stranded wire formed by twisting the first stranded wire, and a third stranded wire formed by twisting the second stranded wire. 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 or polyester.
[0021] As an example, conductor 2 is rope-twisted. Rope twisting is a twisted structure in which the direction of the final (n+1)th twist is opposite to the direction of the twists from the first to the nth twists. Here, n is a natural number of 2 or more. Preferably, n is 2 or 3. Excellent shape stability can be obtained by rope twisting.
[0022] As an example, conductor 2 is made by twisting multiple strands in a Z-shape to form a first stranded wire, twisting multiple first strands in a Z-shape to form a second stranded wire, twisting multiple second strands in an S-shape to form a third stranded wire. As another example, multiple strands are made by twisting multiple strands in a Z-shape to form a first stranded wire, twisting multiple first strands in a Z-shape to form a second stranded wire, twisting multiple second strands in a Z-shape to form a third stranded wire, and twisting multiple third strands in an S-shape to form a fourth stranded wire. As yet another example, multiple strands are made by twisting multiple strands in an S-shape to form a first stranded wire, twisting multiple first strands in an S-shape to form a second stranded wire, twisting multiple second strands in an S-shape to form a third stranded wire, and twisting multiple third strands in a Z-shape to form a fourth stranded wire. Here, Z-twist is synonymous with left-hand twist, and S-twist is synonymous with right-hand twist.
[0023] As an example, conductor 2 uses strands 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 mm². ２ Furthermore, the insulating film has a radial thickness of 0.006 to 0.018 mm.
[0024] [Method for manufacturing the heat-resistant resin layer] The heat-resistant resin layer 3 is formed by extruding molten resin using an annular die and allowing it to cool slowly and solidify. This extrusion molding process integrally forms the heat-resistant resin layer 3 around the conductor 2. According to the manufacturing method of this embodiment, a heat-resistant resin layer 3 that is small in diameter, robust, and highly flexible can be produced.
[0025] [Manufacturing Method for the Outer Sheath] The outer sheath 4 is manufactured using a dedicated die. The dedicated die has a central hole, an inner annular hole formed adjacent to its outer edge so as to surround the central hole, six or more predetermined shaped holes extending radially from the outer circumference of the inner annular hole and wider than the inner annular hole, and an outer annular hole connecting the outer ends of the predetermined shaped holes and wider than the inner annular hole. Using the dedicated die, molten resin is extruded from the inner annular hole, predetermined shaped holes and outer annular hole and slowly cooled and solidified. By forming the outer sheath 4 by this extrusion molding, an inner annular portion 4a, rib portions 4b extending radially from the inner annular portion 4a, and an outer annular portion 4c connecting the outer ends of the rib portions 4b are integrally formed of thermoplastic resin around the heat-resistant resin layer 3. Furthermore, a flow channel 5 is formed that is continuous in the longitudinal direction, surrounded by the inner annular portion 4a, the rib portions 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 made.
[0026] [Air Cooling Test] Next, a sample was prepared and an air cooling test was conducted to confirm the cooling capacity of the power cable 1 described above. The test standard was JIS C2805:2010.
[0027] (Example) The conductor 2 in the sample of the example is a stranded wire using Type 2 polyurethane copper wire with an outer diameter of 0.12 mm. The stranded wire for conductor 2 is made by Z-twisting 12 strands to make the first stranded wire, Z-twisting 6 strands of the first stranded wire to make the second stranded wire, Z-twisting 5 strands of the second stranded wire to make the third stranded wire, and then S-twisting 7 strands of the third stranded wire. The heat-resistant resin layer 3 is extruded from PFA. The radial thickness of the heat-resistant resin layer 3 is 0.4 mm. The outer sheath 4 is made of cross-linked polyethylene resin. The outer sheath 4 has a radial thickness of 0.8 mm in the inner annular portion 4a, a circumferential thickness of 1.4 mm in the rib portion 4b, and a radial thickness of 1.2 mm in the outer annular portion 4c. The outer sheath 4 has six channels 5 formed in it. The power cable 1 in this 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 was left open, and a DC current of 50A was continuously applied to the conductor 2. The surface temperature of each part of the sample was measured using a non-contact thermometer. As a result of continuous current application, the surface temperature of the conductor 2 reached 154°C, and the surface temperature of the outer sheath 4 reached 118°C. Subsequently, room temperature air was introduced as the refrigerant 7 at a flow rate of 70 liters per minute from one end of the sample, and the air was released to the outside from the other end of the sample. After 10 minutes of continuous air cooling, the temperature was measured using a non-contact thermometer. The result showed that the surface temperature of the conductor 2 reached 100°C, and the surface temperature of the outer sheath 4 reached 42°C. Therefore, the example confirmed that by flowing the refrigerant 7, the surface temperature of the conductor 2 was cooled by 54°C, and the surface temperature of the outer sheath 4 was cooled by 76°C.
[0029] In the second air-cooling test, an air coupler was attached to one end of the sample, the other end was left open, and a DC current of 70A was continuously applied to the conductor 2. The surface temperature of each part of the sample was measured using a non-contact thermometer. As a result of continuous current application, the surface temperature of the conductor 2 reached 164°C, and the surface temperature of the outer sheath 4 reached 128°C. Subsequently, room temperature air was introduced as the refrigerant 7 at a flow rate of 70 liters per minute from one end of the sample, and the air was released to the outside from the other end of the sample. After 10 minutes of continuous air cooling, the temperature was measured using a non-contact thermometer. The result showed that the surface temperature of the conductor 2 reached 90°C, and the surface temperature of the outer sheath 4 reached 50°C. Therefore, the example confirmed that by flowing the refrigerant 7, the surface temperature of the conductor 2 was cooled by 74°C, and the surface temperature of the outer sheath 4 was cooled by 78°C.
[0030] (Reference Example) The reference example does not have a heat-resistant resin layer 3. The conductor 2 and outer sheath 4 in the reference example sample are the same as in the example. The outer diameter of the reference example sample is 16.0 The reference example does not have a heat-resistant resin layer 3. The conductor 2 and outer sheath 4 in the reference example sample are the same as 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.
[0031] In the first air-cooling test, an air coupler was attached to one end of the sample, the other end was left open, and a DC current of 50A was continuously applied to conductor 2. The surface temperature of each part of the sample was measured using a non-contact thermometer. As a result of continuous current application, the surface temperature of conductor 2 reached 154°C, and the surface temperature of the outer sheath 4 reached 121°C. Subsequently, room temperature air was introduced as refrigerant 7 at a flow rate of 70 liters per minute from one end of the sample, and the air was released to the outside from the other end. After 10 minutes of continuous air cooling, the temperature was measured using a non-contact thermometer. The result showed that the surface temperature of conductor 2 reached 105°C, and the surface temperature of the outer sheath 4 reached 49°C. Therefore, it was confirmed that in the reference example, the surface temperature of conductor 2 was cooled by 49°C and the surface temperature of the outer sheath 4 was cooled by 72°C by flowing refrigerant 7.
[0032] In the second air-cooling test, an air coupler was attached to one end of the sample, the other end was left open, and a DC current of 70A was continuously applied to conductor 2. The surface temperature of each part of the sample was measured using a non-contact thermometer. As a result of continuous current application, the surface temperature of conductor 2 reached 164°C, and the surface temperature of the outer sheath 4 reached 131°C. Subsequently, room temperature air was introduced as refrigerant 7 at a flow rate of 70 liters per minute from one end of the sample, and the air was released to the outside from the other end of the sample. After 10 minutes of continuous air cooling, the temperature was measured using a non-contact thermometer. The result showed that the surface temperature of conductor 2 reached 94°C, and the surface temperature of the outer sheath 4 reached 52°C. Therefore, it was confirmed that in the reference example, the surface temperature of conductor 2 was cooled by 70°C and the surface temperature of the outer sheath 4 was cooled by 79°C by flowing refrigerant 7.
[0033] The results of the above-mentioned air cooling test confirmed that in both the embodiment and the reference example, the temperature rise of the outer casing 4 could be suppressed by flowing the refrigerant 7 through the flow path 5. Furthermore, it was confirmed that the embodiment with the heat-resistant resin layer 3 could suppress the temperature rise of the outer casing 4 during energization even more effectively than the reference example without the heat-resistant resin layer 3.
Claims
1. A power cable comprising a conductor, a heat-resistant resin layer covering the conductor, and an outer sheath insulating the heat-resistant resin layer, wherein the outer sheath is made of a thermoplastic resin having an integral structure comprising 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 portions, and a flow channel surrounded by the inner annular portion, the rib portions, and the outer annular portion is formed in the same number as the rib portions, and the temperature rise during energization is suppressed by flowing a coolant through the flow channel.
2. The power cable according to claim 1, characterized in that the heat-resistant resin layer is extruded and the thickness of the heat-resistant resin layer is 0.4 to 1.0 mm.
3. The power cable according to claim 2, characterized in that the heat-resistant resin layer is made of polyarylether ketone, polyphenylene sulfide, polyamide-imide, polyimide, polybenzimidazole, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, polytetrafluoroethylene, or tetrafluoroethylene / hexafluoropropylene copolymer.
4. The power cable according to any one of claims 1 to 3, characterized in that it constitutes a power supply line from the power supply unit to the battery in an electric vehicle.