Busbar electric wire

Abstract

To provide a busbar electric wire that allows insulation to be maintained for at least a certain period even under high-temperature conditions and enables reduction of breakage risk during forming processing while retaining manufacturability.SOLUTION: A busbar electric wire 1 includes: a metal busbar 10 formed in a flat shape from pure aluminum or an aluminum alloy; and an insulator 20 covering the metal busbar 10. The insulator 20 has: a silicone resin 21 serving as a main component; and a fire-resistant filler 22 composed of a substance having a second softening point higher than a first softening point, the first softening point being a softening point of the silicone resin 21. The tear-strength / density is 9.7 kN cm3 / m g or more and 23.0 kN cm3 / m g or less, and a residual amount after combustion in heating exceeding the first softening point and below the second softening point is 36 wt.% or more relative to before combustion.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a bus bar wire. [Background technology]

[0002] With the recent spread of BEVs (Battery Electric Vehicles) and the like, battery packs are becoming larger in size in order to extend their driving distances, and there is a demand for such battery packs to be smaller and lighter in weight (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-127630 Summary of the Invention [Problem to be solved by the invention]

[0004] The present applicant is considering replacing the wiring material from round electric wires with flat busbar electric wires in order to reduce the size and weight of battery packs. Such busbar electric wires are long, particularly when they are installed in large battery packs, and have bent portions at predetermined locations to accommodate the wiring configuration. For these reasons, there are limitations to cutting busbar electric wires by press working to a shape that corresponds to the wiring configuration. Therefore, it is preferable to manufacture busbar electric wires in a straight shape and then perform forming to achieve the predetermined bends.

[0005] Furthermore, it is anticipated that high-temperature gases will be emitted from battery packs if a cell malfunctions and causes thermal runaway, so busbar wires must be able to maintain their insulation for a certain period of time even in high-temperature environments.

[0006] One possible solution to this problem is to wrap the conductor in fire-resistant tape and then cover it with insulating resin, but this requires additional tape wrapping work, which makes it difficult to manufacture.

[0007] Therefore, even if fire-resistant silicone, which does not require tape wrapping and can maintain insulation for a certain period of time even in high-temperature environments, is used as the insulating resin, there is a problem in that fire-resistant silicone generally has a small breaking elongation and will break during forming processing.

[0008] The present invention has been made to solve the above-mentioned problems in the related art, and an object of the present invention is to provide a bus bar wire that can ensure insulation for a certain period of time or more even in a high-temperature environment, and that can reduce the possibility of breakage due to forming while ensuring manufacturability. [Means for solving the problem]

[0009] The busbar wire according to the present invention is a busbar wire including a metal busbar formed in a flat shape from pure aluminum or an aluminum alloy, and an insulator covering the metal busbar. The insulator contains a silicone resin as a main component and a fire-resistant filler made of a substance having a second softening point that is higher than a first softening point that is the softening point of the silicone resin, and has a tear strength / density of 9.7 kN cm. 3 / m·g or more 23.0kN·cm 3 / m·g or less, and the amount remaining after combustion when heated to a temperature above the first softening point and below the second softening point is 36 wt % or more of the amount remaining before combustion. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a busbar wire that can ensure insulation for a certain period of time or more even in a high-temperature environment, and that can reduce the possibility of breakage due to forming while ensuring manufacturability. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing a bus bar wire according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the bus bar wire shown in FIG. [Figure 3] 1 is a table showing examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described below in accordance with preferred embodiments. Note that the present invention is not limited to the embodiments shown below and can be modified as appropriate without departing from the spirit of the present invention. In addition, in the embodiments shown below, some components are omitted from illustration and description, but it goes without saying that publicly known or well-known technologies are applied as appropriate to the details of the omitted technologies within the scope of the content described below.

[0013] Fig. 1 is a perspective view showing a busbar wire according to an embodiment of the present invention, and Fig. 2 is a cross-sectional view of the busbar wire shown in Fig. 1. As shown in Figs. 1 and 2, the busbar wire 1 according to this embodiment includes a metal busbar 10 and an insulator 20.

[0014] The metal bus bar 10 is a flat member made of pure aluminum or an aluminum alloy and having a rectangular cross section. Here, the pure aluminum has an aluminum purity of 99.5% or more and may contain inevitable impurities. As shown in Fig. 2, the metal bus bar 10 has a rectangular cross section with corners, but may also have a roughly rectangular cross section without corners.

[0015] The insulator 20 covers the metal bus bar 10 and has an outer shape with a rectangular cross section that matches the shape of the metal bus bar 10. The insulator 20 may have a rectangular cross section with corners, like the metal bus bar 10, or may have a roughly rectangular cross section without corners. The insulator 20 is composed of a silicone resin 21 as a main component and a fire-resistant filler 22 blended into the silicone resin 21. Note that, although the insulator 20 in this embodiment is composed of the silicone resin 21 and the fire-resistant filler 22, it may further include other components, etc., as long as the operation, etc., of this embodiment are not impaired.

[0016] The refractory filler 22 is a so-called refractory inorganic filler, and has a softening point exceeding that of silicone resin. Here, typical silicone resins have a softening point (first softening point) of 350°C or higher and 450°C or lower. Therefore, the refractory filler 22 has a softening point (second softening point) exceeding 350°C, preferably exceeding 450°C. Specifically, the refractory filler 22 has a softening point of 500°C or higher, or 700°C or higher, more preferably exceeding 800°C, and preferably does not soften even in an environment of 800°C for 30 minutes.

[0017] Examples of the refractory filler 22 include high-melting-point glass, wollastonite, and ceramic powder, such as alumina (aluminum oxide), magnesia (magnesium oxide), calcia (calcium oxide), cordierite, silica (silicon dioxide), mullite, zircon, and zirconia (zirconium dioxide).

[0018] The insulator 20 made of the silicone resin 21 containing the fire-resistant filler 22 has a tear strength (crescent shape) (kN / m) that is proportional to the density (g / cm 3 The value obtained by dividing the tear strength by the density is set as the specified range. The specific value obtained by dividing the tear strength by the density is 9.7 kN cm 3 / m·g or more 23.0kN·cm 3 / m·g or less.

[0019] Furthermore, in this embodiment, the busbar wire 1 has a first bent portion 2a (see FIG. 1) bent in the width direction by a bending radius R that is equal to or greater than the width of the metal busbar 10 so that the busbar wire 1 is routed along an appropriate path. The busbar wire 1 also has a second bent portion 2b (see FIG. 1) bent in the thickness direction by a bending radius R that is equal to or greater than the thickness of the metal busbar 10. Note that it is sufficient for the busbar wire 1 to have at least one of the first bent portion 2a or the second bent portion 2b.

[0020] Here, the insulator 20 of the busbar wire 1 has a tear strength / density of 9.7 kN cm 3 / m·g or more 23.0kN·cm 3 / m·g or less. This maintains a good balance between tear strength and density, preventing breakage of the insulator 20 during forming with a bending radius equal to the width in the width direction and a bending radius equal to the thickness in the thickness direction.

[0021] In addition, the insulator 20 is designed so that the amount remaining after combustion at a predetermined heating level is 36 wt% or more of the amount before combustion. Here, the predetermined heating level is a temperature above the softening point of the silicone resin 21 and below the softening point of the refractory filler 22. Here, if the amount of refractory filler 22 is large, the amount of inorganic composite material generated after combustion (after heating) also increases, making it easier for the shape of the insulator to be maintained. In other words, by ensuring that the amount remaining after combustion is 36 wt% or more of the amount before combustion, the insulator 20 is more likely to maintain its shape even after combustion, ensuring its insulating properties.

[0022] Next, examples and comparative examples will be described. Figure 3 is a table showing examples and comparative examples. First, an insulator alone was prepared to measure the following properties. Separately, a busbar wire was prepared by covering a metal busbar with an insulator.

[0023] The insulator was made by uniformly kneading each material using two rolls and then molding it into the specified shape using a press, which is described later. At this time, primary vulcanization was carried out at 120°C for 10 minutes, followed by secondary vulcanization in an oven at 200°C for 4 hours.

[0024] More specifically, the insulator is a blend of a first resin, a second resin, a fire-resistant filler, and a curing agent (vulcanizing agent) to exhibit the characteristics described below and shown in Figure 3. The first resin is a silicone resin containing a fire-resistant filler, designated KE-1734-U by Shin-Etsu Chemical Co., Ltd. The second resin is a high-tear strength silicone resin, designated KE-186-U by Shin-Etsu Chemical Co., Ltd. The fire-resistant filler is wollastonite, designated WP series by Nippon Talc Co., Ltd. The vulcanizing agent is designated C-23N by Shin-Etsu Chemical Co., Ltd.

[0025] Furthermore, the busbar wires according to the examples and comparative examples were produced by extruding a material uniformly kneaded between two rolls through an extruder equipped with a predetermined mandrel together with metal busbars made of pure aluminum and aluminum alloy. The coating thickness was 2 mm. After coating, the wires were subjected to primary vulcanization in a ring furnace heated to 150-300°C, followed by secondary vulcanization at 200°C for 4 hours.

[0026] The metal bus bars used were 5mm wide and 1mm thick, 20mm wide and 3mm thick, and 40mm wide and 5mm thick. In other words, busbar wires with three different dimensions were produced. The pure aluminum used to make the metal bus bars was A1050-H24. This means that it had a purity of 99.5% or higher and was work-hardened by rolling and then moderately annealed to achieve half-hardening (tensile strength: 115 MPa). The aluminum alloy used to make the metal bus bars was A6101. This means that it is an Al-Mg-Si alloy with 0.3-0.7% Si, 0.5% or less Fe, 0.1% or less Cu, 0.03% or less Mn, 0.08-0.35% Mg, 0.03% or less Cr, and 0.1% or less Zn (tensile strength: 178 MPa). In A6101, the total content of V, Bi, Pb, Zr, Ni, etc. is 0.06% or less, and the total content of other substances is 0.03% or less individually and 0.1% or less in total, with the remainder being Al.

[0027] The density (g / cm) of the test specimens of the insulators prepared as described above was measured. 3 ), Shore A hardness, tensile strength (MPa), elongation at break (%), and tear strength (crescent type) (kN / m) were measured.

[0028] The density, hardness, tensile, and tear tests were conducted in accordance with JIS K 6249. Density was measured in accordance with JIS K 6268, 5.1 (Method A). Test specimens were cut from 2 mm thick sheets. Shore A hardness was measured in accordance with JIS K 6253. A Type A durometer was used for the measurements, and measurements were taken on 12.5 mm thick test specimens. Tensile strength and elongation at break were measured in accordance with JIS K 6251. Test specimens were prepared by punching JIS No. 3 dumbbell specimens from 2 mm thick sheets. Tear strength was measured in accordance with JIS K 6250. Test specimens were prepared by punching crescent-shaped specimens from 2 mm thick sheets.

[0029] First, in Comparative Example 1, the insulator had a density of 1.54 (g / cm 3 ), Shore A hardness 74, tensile strength 5.8 (MPa), elongation at break 140 (%), and tear strength (crescent type) 13 (kN / m). Therefore, the tear strength / density was 8.4 kN cm 3 / m·g. The insulator of Comparative Example 1 contains a fire-resistant filler.

[0030] In Comparative Example 2, the insulator had a density of 1.30 (g / cm 3 ), Shore A hardness 62, tensile strength 7.8 (MPa), elongation at break 330 (%), and tear strength (crescent type) 11 (kN / m). Therefore, the tear strength / density was 8.5 kN cm 3 / m·g. The insulator of Comparative Example 2 did not contain any fire-resistant filler.

[0031] In Comparative Example 3, the insulator had a density of 1.22 (g / cm 3), Shore A hardness 60, tensile strength 10.5 (MPa), elongation at break 400 (%), and tear strength (crescent type) 28 (kN / m). Therefore, the tear strength / density was 23.0 kN cm 3 / m·g. The insulator of Comparative Example 3 did not contain any fire-resistant filler.

[0032] In Comparative Example 4, the insulator had a density of 1.52 (g / cm 3 ), Shore A hardness 73, tensile strength 6.1 (MPa), elongation at break 170 (%), and tear strength (crescent type) 14 (kN / m). Therefore, the tear strength / density was 9.2 kN cm 3 / m·g. The insulator of Comparative Example 4 contains a fire-resistant filler.

[0033] In Example 1, the insulator has a density of 1.51 (g / cm 3 ), Shore A hardness 72, tensile strength 6.3 (MPa), elongation at break 200 (%), and tear strength (crescent type) 15 (kN / m). Therefore, the tear strength / density was 9.9 kN cm 3 / m·g. The insulator of Example 1 contains a fire-resistant filler.

[0034] In Example 2, the insulator has a density of 1.34 (g / cm 3 ), Shore A hardness 74, tensile strength 6.3 (MPa), elongation at break 240 (%), and tear strength (crescent type) 13 (kN / m). Therefore, the tear strength / density was 9.7 kN cm 3 / m·g. The insulator of Example 2 contains a fire-resistant filler.

[0035] In Example 3, the insulator has a density of 1.31 (g / cm 3 ), Shore A hardness 71, tensile strength 6.5 (MPa), elongation at break 260 (%), and tear strength (crescent type) 15 (kN / m). Therefore, the tear strength / density was 11.5 kN cm 3 / m·g. The insulator of Example 3 contains a fire-resistant filler.

[0036] In Example 4, the insulator has a density of 1.47 (g / cm 3 ), Shore A hardness 71, tensile strength 6.8 (MPa), elongation at break 250 (%), and tear strength (crescent type) 17 (kN / m). Therefore, the tear strength / density was 11.6 kN cm 3 / m·g. The insulator of Example 4 contains a fire-resistant filler.

[0037] In Example 5, the insulator had a density of 1.44 (g / cm 3 ), Shore A hardness 70, tensile strength 7.3 (MPa), elongation at break 300 (%), and tear strength (crescent type) 19 (kN / m). Therefore, the tear strength / density was 13.2 kN cm 3 / m·g. The insulator of Example 5 contains a fire-resistant filler.

[0038] In Example 6, the insulator has a density of 1.40 (g / cm 3 ), Shore A hardness 68, tensile strength 7.9 (MPa), elongation at break 360 (%), and tear strength (crescent type) 21 (kN / m). Therefore, the tear strength / density was 15.0 kN cm 3 / m·g. The insulator of Example 6 contains a fire-resistant filler.

[0039] In Example 7, the insulator has a density of 1.36 (g / cm 3 ), Shore A hardness 67, tensile strength 8.4 (MPa), elongation at break 420 (%), and tear strength (crescent type) 23 (kN / m). Therefore, the tear strength / density was 16.9 kN cm 3 / m·g. The insulator of Example 7 contains a fire-resistant filler.

[0040] In Example 8, the insulator had a density of 1.30 (g / cm 3), Shore A hardness 65, tensile strength 9.4 (MPa), elongation at break 520 (%), and tear strength (crescent type) 27 (kN / m). Therefore, the tear strength / density was 20.8 kN cm 3 / m·g. The insulator of Example 8 contains a fire-resistant filler.

[0041] In Comparative Example 5, the insulator had a density of 1.26 (g / cm 3 ), Shore A hardness 63, tensile strength 10.0 (MPa), elongation at break 580 (%), and tear strength (crescent type) 29 (kN / m). Therefore, the tear strength / density was 23.0 kN cm 3 / m·g. The insulator of Comparative Example 5 contains a fire-resistant filler.

[0042] Bending tests and fire resistance tests were conducted on the above-described Examples 1 to 8 and Comparative Examples 1 to 5. The bending tests were conducted by cutting the busbar wires prepared as described above to approximately 500 mm pieces and bending the resulting test pieces with a bending machine. The bending was conducted in the width direction with a radius equal to the width of the wire, and also in the thickness direction with a radius equal to the thickness of the wire. If the insulator did not break due to this bending, it was marked as "Good", and if the insulator broke, it was marked as "Poor". Note that the results of the bending tests were the same for all three types of busbar wires with different dimensions and regardless of the bending direction, so they are shown together in the figures, etc., rather than as individual results.

[0043] Furthermore, fire resistance tests were conducted on test specimens obtained by cutting the busbar wires prepared as described above to approximately 500 mm. Based on JECTEC's fire-resistant and heat-resistant wire certification standards, the maximum inter-fixture length of an automotive busbar was assumed to be 1 m. A load equivalent to the 1 m length was applied to the test specimens, which were then placed in a muffle furnace and heated from room temperature until the temperature reached 800°C. The specimens were then held for 30 minutes. During this heating period, an insulation resistance tester was connected to the insulators to constantly measure their insulation resistance. A test specimen that maintained a resistance of 0.4 MΩ or greater by the end of heating was marked with a "Good" mark. A test specimen that fell below 0.4 MΩ by the end of heating was marked with a "Poor" mark.

[0044] Furthermore, after the fire resistance test, the weight of the remaining insulator alone was measured to confirm what wt% it corresponded to before combustion.

[0045] As a result of these tests, in the bending test of Comparative Example 1, the pure aluminum was given a "good" grade, but the aluminum alloy was given a "bad" grade. The fire resistance test was also given a "good" grade, with the remaining amount being 85 wt%.

[0046] The reason why the bending test results differ between pure aluminum and aluminum alloy is thought to be due to the difference in conductor strength. In other words, the stronger the material, the greater the force required to bend it, and as a result, the greater the stress on the insulating coating. For this reason, the bending test results differ between pure aluminum and aluminum alloy metal bus bars.

[0047] In Comparative Example 2, both pure aluminum and aluminum alloy were evaluated as "X" in the bending test. The fire resistance test was also evaluated as "X". In Comparative Example 2, no fire-resistant filler was blended, and the remaining amount was 0 wt%.

[0048] In Comparative Example 3, both pure aluminum and aluminum alloy were evaluated as "Good" in the bending test. However, the fire resistance test was evaluated as "Poor." In Comparative Example 3, similar to Comparative Example 2, no fire-resistant filler was blended, and the remaining amount was 0 wt%.

[0049] In Comparative Example 4, the pure aluminum was given a "good" grade in the bending test, but the aluminum alloy was given a "bad" grade. The fire resistance test was also given a "good" grade, with a remaining amount of 82 wt%.

[0050] In Example 1, the bending test was performed with both pure aluminum and aluminum alloy, resulting in a result of "Good." The fire resistance test was also performed with a result of "Good," with a remaining amount of 80 wt%. In Example 2, the bending test was performed with both pure aluminum and aluminum alloy, resulting in a result of "Good." The fire resistance test was also performed with a result of "Good," with a remaining amount of 69 wt%.

[0051] In Examples 3 to 8, the bending test was "Good" for both pure aluminum and aluminum alloy, and the fire resistance test was also "Good." The remaining amounts in Examples 3 to 8 were 47 wt%, 74 wt%, 68 wt%, 61 wt%, 53 wt%, and 36 wt%, respectively.

[0052] In Comparative Example 5, the bending test gave a score of "Good" for both pure aluminum and aluminum alloy, but the fire resistance test gave a score of "Poor", with the remaining amount being 25 wt%.

[0053] According to the above Examples 1 to 8 and Comparative Examples 1 to 5, the tear strength / density value was 9.7 kN cm 3 / m·g or more 23.0kN·cm 3 When the residual content was 36 wt% or more, both pure aluminum and aluminum alloys were evaluated as "good" in the bending test.

[0054] Therefore, the residual amount of silicone resin should be 36 wt% or more, and the tear strength / density value should be 9.7 kN cm 3 / m·g or more 23.0kN·cm 3 It was found that it is preferable to include a refractory filler so that the densities are kept below / m·g.

[0055] Thus, in the busbar wire 1 according to this embodiment, the insulator 20 contains the fire-resistant filler 22 made of a substance with a softening point higher than that of the silicone resin 21, and the amount remaining after combustion by heating is 36 wt % or more of the amount before combustion. That is, the insulator 20 contains the fire-resistant filler 22 in an amount corresponding to the remaining amount, and the presence of this amount of fire-resistant filler 22 ensures insulation for a certain period of time even in high-temperature environments. Furthermore, because the insulator 20 alone can withstand high-temperature environments, there is no need to wrap it with fire-resistant tape, ensuring manufacturability.

[0056] Furthermore, as the refractory filler 22 is blended into the silicone resin 21, the density increases due to the weight of the refractory filler 22, but the tear strength decreases because the resin is more likely to tear from the location where the refractory filler 22 is present. For this reason, blending too much refractory filler 22 can lead to breakage during forming. However, the tear strength / density is 9.7 kN cm. 3 / m·g or more 23.0kN·cm 3 / m·g or less, the balance between tear strength and density is well-balanced, there are no problems with fire resistance, and it is also designed not to break during forming processing. In particular, the tear strength / density is 9.7kN·cm 3 / m·g or more 23.0kN·cm 3 / m·g or less, ensuring a tear strength suitable for aluminum-based conductors, which only require a relatively small force when bending.

[0057] Therefore, it is possible to provide the bus bar wire 1 that can ensure insulation for a certain period of time or more even in a high-temperature environment, and that can reduce the possibility of breakage due to forming while ensuring manufacturability.

[0058] The busbar wire 1 also has at least one first bent portion 2a bent in the width direction by a bending radius R equal to or greater than the width of the metal busbar 10, or one second bent portion 2b bent in the thickness direction by a bending radius R equal to or greater than the thickness of the metal busbar 10. This makes it possible to provide a busbar wire 1 in which the insulator 20 does not break even when a forming process is performed.

[0059] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and modifications may be made within the scope of the spirit of the present invention, and if possible, publicly known or well-known technologies may be combined.

[0060] In the above examples, examples of pure aluminum and aluminum alloys have been described, but the pure aluminum does not have to be A1050-H24, and the aluminum alloy does not have to be A6101.

[0061] Furthermore, in the above examples, the fire resistance test was performed at 800°C, and the results are shown. Experiments were also performed at 500°C and 700°C, but the results were the same as those at 800°C, so a description of these temperatures is omitted above. For example, if the maximum temperature in the environment to which the busbar wire 1 may be exposed is 500°C or 700°C, the fire resistance test may be performed at 500°C or 700°C. Furthermore, insulation can be ensured as long as 36 wt% or more of the insulator remains after the fire resistance test. Therefore, for example, if the maximum temperature in the environment to which the busbar wire 1 may be exposed is 500°C or 700°C, it is sufficient that 36 wt% or more of the insulator remains after the fire resistance test at 500°C or 700°C. [Explanation of symbols]

[0062] 1: Busbar wire 2a: 1st bending part 2b: 2nd bending part 10: Metal bus bar 20: Insulator 21: Silicone resin 22: Refractory filler

Claims

1. A busbar electric wire including a metal busbar formed in a flat shape from pure aluminum or an aluminum alloy, and an insulator covering the metal busbar, The insulator has a silicone resin as a main component and a fire-resistant filler made of a substance having a second softening point higher than a first softening point that is the softening point of the silicone resin, and has a tear strength / density of 9.7 kN cm ３ / m・g or more 23.0kN・cm ３ / m·g or less, and the residual amount after combustion when heated to a temperature exceeding the first softening point and lower than the second softening point is 36 wt % or more of the amount before combustion. A busbar wire characterized by:

2. The metal bus bar has at least one first bent portion bent in the width direction by a bending radius R equal to or greater than the width of the metal bus bar, or at least one second bent portion bent in the thickness direction by a bending radius R equal to or greater than the thickness of the metal bus bar. The bus bar wire according to claim 1 .

Images