Power cable

Abstract

The objective is to provide a power cable 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 that can quickly cool the conductor heat. [Solution] The power cable 1 comprises a conductor 2, a heat-resistant resin layer 3 covering the conductor 2, and an outer sheath 4 insulating the heat-resistant resin layer 3. The outer sheath 4 consists of 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. A flow path 5 surrounded by the inner annular portion 4a, the rib portions 4b, and the outer annular portion 4c is formed in the same number as the rib portions 4b. The power cable 1 is configured to suppress the temperature rise of the outer sheath 4 when energized by flowing a coolant 7 through the flow path 5.

Description

Technical Field

[0001] The present invention relates to a power cable for power supply.

Background Art

[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). Also, 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).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[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 necessary for cooling the conductor heat generation during energization. Also, since the cross-section is 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 when 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 aims to provide a power cable having a heat-resistant structure that can withstand conductor heating caused by excessive currents such as inrush currents, while also having a cooling structure that can quickly cool the conductor heating. [Means for solving the problem]

[0007] The power cable according to the present invention comprises a conductor, a heat-resistant resin layer covering the conductor, and an outer sheath insulating the heat-resistant resin layer. The outer sheath is made of a thermoplastic resin with 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. A flow channel is formed by the inner annular portion, the rib portions, and the outer annular portion, with the same number of channels as the rib portions. The heat-resistant resin layer is formed by overlapping windings of heat-resistant resin tape, and the power cable is configured to suppress temperature rise during energization by flowing a coolant through the flow channel.

[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. The heat-resistant resin layer is formed by overlapping heat-resistant resin tape, making it easy to manufacture. Moreover, the overlapping heat-resistant resin tape allows for a thin tape that is easy to wrap around the conductor, while also creating an air layer between the heat-resistant layers of the heat-resistant resin tape, thus further improving heat resistance. Therefore, 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] Preferably, the first layer of the heat-resistant resin layer that is in contact with the conductor consists of one or more of polyimide, polyamideimide, and polyamide. These heat-resistant resins have a heat resistance temperature of over 200°C and can sufficiently withstand the heat generated by the conductor due to overcurrent.

[0010] Preferably, the outer layer of the heat-resistant resin layer, which is outside the first layer, is made of polyphenylene sulfide or liquid crystal polymer. The first layer of the heat-resistant resin layer that is in contact with the conductor absorbs the most thermal energy from the conductor's heat generation. In other words, the heat-generating temperature of the heat-resistant resin layer tends to decrease as it becomes an outer layer. By providing the first layer of the heat-resistant resin layer as a single winding of polyimide or the like, which has the highest heat resistance, and providing the second and third outer layers as multiple windings of polyphenylene sulfide or the like, which has high heat resistance and low material cost, it is possible to reduce material costs while maintaining heat resistance performance against conductor heat generation.

[0011] This configuration offers 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. [Effects of the Invention]

[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. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a power cable according to this embodiment. [Figure 2] Figure 2 is a schematic diagram illustrating an example of the power cable shown in Figure 1. [Figure 3] Figure 3 is a schematic diagram showing an example of the application of a power cable according to this embodiment. [Modes for carrying out the invention]

[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 the 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 all the figures 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 Cables] 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 enclosed 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 formed by overlapping windings of heat-resistant resin tape. 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 the outer sheath portion 4 from melting. Preferably, the heat-resistant resin layer 3 consists of both a first layer 3a in contact with the conductor 2 and an outer layer 3b provided on the outside of the first layer 3a. Preferably, the first layer 3a has a heat resistance temperature of 200°C or higher. The first layer 3a may be a single winding, a double winding, or a multi-wound winding. By making the first layer 3a a single winding, the material cost can be minimized. Preferably, the outer layer 3b covering the first layer 3a has a heat resistance temperature of 160°C or higher. The outer layer 3b may be a single winding, a double winding, or a multi-wound winding. By making the outer layer 3b a single winding, the material cost can be minimized. By making the number of turns in the first layer 3a less than the number of turns in the outer layer 3b, it is possible to increase heat resistance while reducing material costs. In particular, by making the first layer 3a a single layer and the outer layer 3b a single layer, it is possible to increase heat resistance while minimizing 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 FIG. 2, the power cable 1 of the present embodiment is configured to suppress the temperature rise of the outer covering portion 4 during energization by flowing the refrigerant 7 through the flow path 5. As an example, the refrigerant 7 is antifreeze or an inert liquid or water. As an example, the coolant used for the in-vehicle battery 51b is branched and used as the refrigerant 7. Then, the refrigerant 7 is taken in from one end side of the power cable 1, flowed, discharged from the other end side of the power cable 1, and refluxed to the cooling device used for the in-vehicle battery 51b. Thereby, the power cable 1 can be cooled. The arrow in FIG. 2 indicates the traveling direction of the refrigerant 7. As a configuration other than the above, 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 side of the power cable 1, flowed, and discharged to the outside from the other end side 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 film such as an oxide film is formed on the outer periphery of a metal wire made of copper, a copper alloy, aluminum, or an aluminum alloy. The conductor 2 may be a stranded wire. When the conductor 2 is a stranded wire, it is an aggregate of strands in which an insulating film such as an oxide film is formed on the outer periphery of a metal wire made of copper, a copper alloy, aluminum, or an aluminum alloy. As an example, the conductor 2 has a composite stranding structure having a first stranded wire obtained by stranding strands, a second stranded wire obtained by stranding the first stranded wire, and a third stranded wire obtained by stranding the second stranded wire. The insulating film is preferably made of a material that does not interfere with soldering. As an example, the insulating film is made of polyurethane, polyester, or the like.

[0021] As an example, the conductor 2 is rope-stranded. Rope stranding is a stranding structure in which, in a stranded wire, the final (n + 1)-th stranding direction is opposite to the stranding direction from the first stranding direction to the n-th stranding direction. Here, n is a natural number of 2 or more. Preferably, n is 2 or 3. Excellent shape stability can be obtained by rope stranding.

[0022] As an example, conductor 2 is formed by twisting multiple strands in a Z-shape to form a first strand, twisting multiple first strands in a Z-shape to form a second strand, twisting multiple second strands in an S-shape to form a third strand. As another example, multiple strands are twisted in a Z-shape to form a first strand, twisting multiple first strands in a Z-shape to form a second strand, twisting multiple second strands in a Z-shape to form a third strand, and twisting multiple third strands in an S-shape to form a fourth strand. As yet another example, multiple strands are twisted in an S-shape to form a first strand, twisting multiple first strands in an S-shape to form a second strand, twisting multiple second strands in a Z-shape to form a third strand. As yet another example, multiple strands are twisted in an S-shape to form a first strand, twisting multiple first strands in an S-shape to form a second strand, twisting multiple second strands in an S-shape to form a third strand, and twisting multiple third strands in a Z-shape to form a fourth strand. 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 consisting 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 a heat-resistant resin layer] The heat-resistant resin layer 3 is formed by winding multiple layers of heat-resistant resin tape. The first layer 3a of the heat-resistant resin layer 3 consists of one or more of polyimide, polyamideimide, or polyamide. These heat-resistant resins have a heat resistance temperature of over 200°C and can sufficiently withstand the heat generated by the conductor 2 due to 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, which is opposite to the first direction, which is the twisting direction of the conductor 2. This prevents the formation of wrinkles in the first layer 3a.

[0025] The heat-resistant resin layer 3 consists of an outer layer 3b made of polyphenylene sulfide or liquid crystal polymer, located outside the first layer 3a. These heat-resistant resins have a heat resistance temperature of over 160°C and can sufficiently withstand the heat generated by the conductor 2 in the first layer 3a. 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, which is opposite to the second direction, which is the winding direction of the first layer 3a. This prevents the formation of wrinkles 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, the heat-resistant resin layer 3 can be easily manufactured. Furthermore, by winding the heat-resistant resin tape in multiple layers, a thin tape that is easy to wrap around the conductor 2 is created, and an air layer is formed between the heat-resistant layers of the heat-resistant resin tape, so further improvement in heat resistance can be expected.

[0027] [Manufacturing method for the outer covering] The outer sheath portion 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 portion 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.

[0028] [Air cooling test] Next, a sample was prepared and an air-cooling test was conducted to confirm the cooling capacity of the aforementioned power cable 1. The test standard was JIS C2805:2010.

[0029] (Examples) 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 formed 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 formed by single-wrapping a 0.05 mm thick, 30 mm wide heat-resistant resin tape made of polyimide as the first layer 3a with an overlap ratio of 1 / 4, and double-wrapping a 0.1 mm thick, 30 mm wide heat-resistant resin tape made of polyphenylene sulfide as the outer layer 3b outside the first layer 3a with an overlap ratio of 1 / 4. The thickness of the heat-resistant resin layer 3 is 0.35 mm. The outer sheath 4 is made of cross-linked polyethylene resin. The outer sheath 4 has a radial thickness of 0.8 mm for the inner annular portion 4a, a circumferential thickness of 1.4 mm for the rib portion 4b, and a radial thickness of 1.2 mm for the outer annular portion 4c. The outer sheath 4 has six channels 5 formed within it. The power cable in this 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 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 118°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 100°C, and the surface temperature of the outer sheath 4 reached 42°C. Therefore, this example confirmed that by flowing refrigerant 7, the surface temperature of conductor 2 was cooled by 54°C, and the surface temperature of the outer sheath 4 was cooled by 76°C.

[0031] 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 128°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 90°C, and the surface temperature of the outer sheath 4 reached 50°C. Therefore, the example confirmed that by flowing refrigerant 7, the surface temperature of conductor 2 was cooled by 74°C, and the surface temperature of the outer sheath 4 was cooled by 78°C.

[0032] (Reference example) The reference example does not have the 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 in 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 was left open, and a continuous current of 50A DC was 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 was 105°C, and the surface temperature of the outer sheath 4 was 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.

[0034] 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.

[0035] The results of the above-mentioned air cooling tests 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. [Explanation of Symbols]

[0036] 1 Power cable 2 strands 3 Heat-resistant resin layer, 3a 1st layer, 3b outer layer 4 outer cover portion, 4a inner annular portion, 4b rib portion, 4c outer annular portion 5 channels 7 Refrigerant 51 Electric vehicle, 51a Power supply unit, 51b Battery

Claims

1. It comprises a conductor, a heat-resistant resin layer covering the conductor, and an outer covering that insulates the heat-resistant resin layer. The outer covering portion 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 the number of flow channels enclosed by the inner annular portion, the rib portions, and the outer annular portion is the same as the number of rib portions. The heat-resistant resin layer is formed by overlapping and winding heat-resistant resin tape. The configuration suppresses the temperature rise when power is applied by flowing a refrigerant through the aforementioned flow path. A power cable characterized by the following features.

2. The heat-resistant resin layer is such that the first layer in contact with the conductor is made of one or more of polyimide, polyamideimide, or polyamide. The power cable according to claim 1, characterized by the following:

3. The heat-resistant resin layer has an outer layer that is outside the first layer, which is made of polyphenylene sulfide or liquid crystal polymer. The power cable according to claim 2, characterized by the following:

4. To configure a power supply line from the power supply unit to the battery in an electric vehicle. A power cable according to any one of claims 1 to 3, characterized by the following:

Images