In-vehicle bus bar and method for manufacturing same

Abstract

This in-vehicle bus bar has a metal bar and an insulating fireproof tape partially overlapping the metal bar and laterally wound to cover the metal bar. The in-vehicle bus bar includes a straight part and a bent part. Assuming that the outer circumferential length of the in-vehicle bus bar in the bent part is L1, the median circumferential length of the in-vehicle bus bar in the bent part is L2, the width of the insulating fireproof tape is W1, and the overlapping width of the insulating fireproof tape in the straight part is W2, the elongation percentage A (%) of the outer circumferential length L1 with respect to the median circumferential length L2 is smaller than the ratio B (%) of the overlapping width W2 of the insulating fireproof tape to the width W1 of the insulating fireproof tape.　Equation (1): A = (L1 / L2 - 1) × 100, Equation (2): B = (W2 / W1) × 100

Description

Vehicle bus bar and manufacturing method thereof

[0001] The present invention relates to a bus bar suitable for in-vehicle use and a method for manufacturing the same.

[0002] In electric vehicles such as BEVs (Battery Electric Vehicles) and HEVs (Hybrid Electric Vehicles), bus bars are used to supply power between a battery unit and an inverter. In recent electric vehicles, not only the motor but also the brakes, steering, doors, and windows are electrically operated. Therefore, if a driver needs to leave the electric vehicle due to an accident or a fire caused by poor maintenance, the power supply system, including the battery unit and bus bars, is required to maintain a power supply for a certain period of time and keep the electrical components running, ensuring time for evacuation and notification. Lithium-ion batteries, which are widely used as batteries, are prone to deformation and fire due to external heating or self-heating, so the unit is protected in a robust, fire-resistant container. Furthermore, bus bars must be efficiently routed in the limited space around the battery and must be fire-resistant.

[0003] Patent Document 1 describes a busbar wire having a flat conductor and an insulating coating covering the flat conductor. The insulating coating is formed into a tube shape using a heat-shrinkable material such as polyolefin, polyvinyl chloride, or fluorine-based resin. In this busbar wire, the flat conductor is placed inside the insulating coating, and the insulating coating is thermally shrunk using a heat gun, iron, or the like, to cover the flat conductor with the insulating coating.

[0004] Japanese Patent Application Laid-Open No. 2022-6856

[0005] However, in the busbar wire of Patent Document 1, the insulating coating is formed of a fluorine-based resin or the like, which limits its elongation characteristics. Therefore, if the busbar wire is bent after the flat conductor is coated with the insulating coating, the insulating coating may be torn. Therefore, when forming a busbar wire with a bent portion, it is necessary to bend the flat conductor and then coat it with the insulating coating, which is thought to increase the number of work steps.

[0006] Therefore, a main object of the present invention is to provide an in-vehicle bus bar that maintains fire resistance even when subjected to subsequent bending without increasing the number of work steps, and a method for manufacturing the same.

[0007] In order to solve the above problems, one aspect of the present invention provides an in-vehicle busbar having a metal bar and an insulating fire-resistant tape that is wound transversely and partially overlaps the metal bar to cover the metal bar, the in-vehicle busbar including a straight portion and a bent portion, and wherein, when the outer periphery of the in-vehicle busbar at the bent portion is L1, the central periphery of the in-vehicle busbar at the bent portion is L2, the width of the insulating fire-resistant tape is W1, and the overlap width of the insulating fire-resistant tape at the straight portion is W2, an elongation percentage A (%) of the outer periphery length L1 to the central periphery length L2, as shown in the following formula (1), is smaller than a ratio B (%) of the overlap width W2 of the insulating fire-resistant tape to the width W1 of the insulating fire-resistant tape, as shown in the following formula (2): Formula (1): A = (L1 / L2 - 1) x 100 Formula (2): B = (W2 / W1) x 100

[0008] According to another aspect of the present invention, there is provided a method for manufacturing an on-vehicle busbar, comprising the steps of: coating a metal bar by partially overlapping and laterally winding an insulating fire-resistant tape around the metal bar; and edgewise bending a portion of the metal bar coated with the insulating fire-resistant tape to form a straight portion and a bent portion, wherein, when the outer periphery of the on-vehicle busbar at the bent portion is L1, the central periphery of the on-vehicle busbar at the bent portion is L2, the width of the insulating fire-resistant tape is W1, and the overlap width of the insulating fire-resistant tape in a region corresponding to the bent portion before edgewise bending is W2, an elongation percentage A (%) of the outer periphery length L1 to the central periphery length L2, as shown in the following formula (1), is smaller than a ratio B (%) of the overlap width W2 of the insulating fire-resistant tape to the width W1 of the insulating fire-resistant tape, as shown in the following formula (2): Equation (1): A = (L1 / L2 - 1) x 100 Equation (2): B = (W2 / W1) x 100

[0009] According to the present invention, it is possible to provide an in-vehicle bus bar that maintains fire resistance even when subjected to subsequent bending without increasing the number of work steps, and a method for manufacturing the same.

[0010] 1A and 1B are diagrams showing the configuration of an on-board bus bar. FIGS. 2A and 2B are diagrams for explaining edgewise bending of an on-board bus bar according to an embodiment. FIGS. 3A and 3B are diagrams for explaining edgewise bending of an on-board bus bar that is not according to this embodiment. FIG. 4 is a flowchart of a method for manufacturing an on-board bus bar. FIGS. 5A and 5B are diagrams for explaining a step of coating a metal bar. These diagrams show modified examples of the above.

[0011] In-vehicle busbars according to preferred embodiments of the present invention will be described below. In this specification, the term "to" indicating a range of values ​​means that the range includes both the lower limit and the upper limit.

[0012] (Configuration of Vehicle-Mounted Bus Bar) FIG. 1A is a perspective view showing the configuration of a vehicle-mounted bus bar 10, and FIG. 1B is a cross-sectional view of a straight portion.

[0013] The vehicle bus bar 10 has a metal bar 20 and an insulating fire-resistant tape 30. In addition to the above configuration, the vehicle bus bar 10 may also have an insulating layer 40. As shown in FIGS. 1A and 1B , in this embodiment, the vehicle bus bar 10 has a metal bar 20, an insulating fire-resistant tape 30, and an insulating layer 40. The insulating fire-resistant tape 30 is wrapped transversely around the metal bar 20. In this embodiment, the vehicle bus bar 10 has a plurality of straight portions 11 and a plurality of bent portions 12. The plurality of bent portions 12 include first bent portions 13 that are bent edgewise and second bent portions 14 that are bent flatwise.

[0014] The metal bar 20 is a plate-shaped member made of a conductive metal material. The material of the metal bar 20 is not particularly limited as long as it is a metal. Examples of materials for the metal bar 20 include copper or a copper alloy. The metal bar 20 may be made of a single metal plate or may be made of multiple stacked thin metal plates. The thickness and width of the metal bar 20 are determined appropriately depending on the magnitude of the current, the installation location, the installation conditions, etc. When the metal bar 20 is made of multiple stacked thin metal plates, the thickness of the thin metal plates is within the range of 0.1 to 0.3 mm. Furthermore, the metal bar 20 made of multiple stacked thin metal plates may have both ends welded together, giving it a flexible structure that can be twisted or bent.

[0015] For example, one end of the metal bar 20 is connected to one of the batteries, and the other end is connected to an inverter. If the battery terminals are bolt-type, the connection between the battery and the vehicle bus bar 10 (metal bar 20) can be firmly fixed by fitting the terminals into the holes 21 formed at both ends of the metal bar 20 and fastening them with nuts.

[0016] The insulating fire-resistant tape 30 covers the metal bar 20. The type of insulating fire-resistant tape 30 is not particularly limited as long as it has insulating properties. Examples of insulating fire-resistant tape 30 include silicone tape and mica tape. In this embodiment, the insulating fire-resistant tape 30 (silicone tape) may have a silicone tape layer 31 and a glass tape layer 32 laminated on the silicone tape layer 31. The glass tape layer 32 includes a flat braided glass fiber. In this embodiment, the insulating fire-resistant tape 30 is a silicone tape having a silicone tape layer 31 and a glass tape layer 32 laminated on the silicone tape layer 31. In this embodiment, the glass tape layer 32 is in contact with the metal bar 20, and the silicone tape layer 31 is located on the outer periphery. On the other hand, the mica tape also exhibits insulating properties at high temperatures. Mica is a natural mineral (called mica in Japanese) and has excellent electrical insulation and heat resistance. Although mica is a mineral, when formed into tape, it exhibits good flexibility, making it a material suitable for bending or curving. The mica tape may be a glass mica tape in which mica is adhered to a glass cloth, or a plastic mica tape in which mica is adhered to a plastic film made of polyethylene or the like.

[0017] The thickness of the insulating fireproof tape 30 is preferably within the range of 0.1 to 0.5 mm. If the thickness of the insulating fireproof tape 30 is less than 0.1 mm, fire resistance and insulation properties may not be ensured. On the other hand, if the thickness of the insulating fireproof tape 30 exceeds 0.5 mm, it may not be possible to properly wrap the insulating fireproof tape 30 horizontally around the metal bar 20. The width of the insulating fireproof tape 30 is preferably within the range of 10 to 50 mm. If the width of the insulating fireproof tape 30 is less than 10 mm, workability may be reduced. On the other hand, if the width of the insulating fireproof tape 30 exceeds 50 mm, the angle formed between the metal bar 20 and the insulating fireproof tape 30 becomes small during tape wrapping, and the end of the insulating fireproof tape 30 may lift up.

[0018] The insulating layer 40 covers the insulating fire-resistant tape 30. The material of the insulating layer 40 is a flame-retardant resin. Examples of materials for the insulating layer 40 include polyamide (PA), polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP).

[0019] Here, the horizontal winding will be described in detail. Fig. 2A is a plan view of a straight vehicle busbar 10 from which the insulator layer 40 has been removed, and Fig. 2B is a plan view of the vehicle busbar 10 having an edgewise bent first bent portion 13 from which the insulator layer 40 has been removed. Fig. 3A is a plan view of another straight vehicle busbar 10 from which the insulator layer 40 has been removed, and Fig. 3B is a plan view of another vehicle busbar 10 having an edgewise bent first bent portion 13 from which the insulator layer 40 has been removed. The overlap width W2 of the insulating fire-resistant tape 30 in Fig. 2A is longer than the overlap width W2 of the insulating fire-resistant tape 30 in Fig. 3A. Here, a case where the vehicle busbar is bent edgewise to form a bend angle θ of 90° will be described, but the present invention can also be applied to a case where the vehicle busbar is bent flatwise.

[0020] Assume that a straight automotive busbar 10 as shown in Figures 2A and 3A is edgewise bent to have a first bent portion 13 as shown in Figures 2B and 3B. Specifically, the busbar is edgewise bent at a bending angle θ about a bending center C so that L1' shown in Figures 2A and 3A becomes the circumferential length L1 shown in Figures 2B and 3B, and L2' shown in Figures 2A and 3A becomes the central circumferential length L2 shown in Figures 2B and 3B. In this case, the circumferential length L1 is longer than L1', and the central circumferential length L2 is the same as L2'.

[0021] 2B and 3B , the vehicle-mounted bus bar 10 of this embodiment has a first bent portion 13 formed between two straight portions 11. When the outer circumferential length of the vehicle-mounted bus bar 10 at the first bent portion 13 is L1, the central circumferential length of the vehicle-mounted bus bar 10 at the first bent portion 13 is L2, the width of the insulating fire-resistant tape 30 is W1, and the overlap width of the insulating fire-resistant tape 30 at the straight portion 11 is W2, the elongation percentage A (%) of the outer circumferential length L1 to the central circumferential length L2, as shown in the following formula (1), is smaller than the ratio B (%) of the overlap width W2 of the insulating fire-resistant tape 30 to the width W1 of the insulating fire-resistant tape 30, as shown in the following formula (2). Formula (1): A = (L1 / L2 - 1) × 100 Formula (2): B = (W2 / W1) × 100

[0022] When the width of the vehicle-mounted busbar 10 is Wd, the distance from the bending center C of the first bent portion 13 to the vehicle-mounted busbar 10 is r1, and the bending angle is θ, the outer circumferential length L1 is expressed by the following formulas (3) and (4): L1 = 2 × r3 × π × (θ / 360) in formula (3), and r3 = Wd + r1 in formula (4).

[0023] The central circumferential length L2 is expressed by the following formulas (5) and (6): L2=2×r2×π×(θ / 360) (Formula (5)) r2=0.5×Wd+r1 (Formula (6))

[0024] The elongation percentage A (%) of the circumferential length L1 relative to the central circumferential length L2, as shown in Equation (1), indicates how much the length L1' corresponding to the circumferential length L1 elongates after bending relative to the length before bending. The fact that the elongation percentage A (%) is smaller than the percentage B (%) indicates that even when the vehicle bus bar 10 is bent around the bending center C, the metal bar 20 is not exposed in the peripheral region away from the bending center C. During edgewise bending, as L1' elongates to the circumferential length L1, the insulating fire-resistant tape 30 shifts position so that the overlapping portion is gradually released. However, as shown in FIGS. 2A and 2B , in this embodiment, the elongation percentage A (%) is smaller than the percentage B (%), so the metal bar 20 is not exposed in the peripheral region away from the bending center C. Furthermore, in this embodiment, because the insulating fire-resistant tape 30 shifts position, the insulating fire-resistant tape 30 does not break even in the region outside the bent portion 12.

[0025] The ratio B (%) is preferably 50% or less. If the ratio B (%) exceeds 50%, the insulating fire-resistant tape 30 will be partially triple-layered, which may result in the insulating fire-resistant tape 30 not being properly positioned when the bent portion 12 is formed.

[0026] Furthermore, the above-described formulas (1) and (2) may be satisfied only in the region where the bent portion 12 is formed, or may be satisfied over the entire vehicle bus bar 10. By horizontally winding the insulating fire-resistant tape 30 so that the above formulas (1) and (2) are satisfied only in the region where the bent portion 12 is formed, it is possible to reduce consumption of the insulating fire-resistant tape 30. In this embodiment, the insulating fire-resistant tape 30 is horizontally wound so that the overlap width is constant over the entire vehicle bus bar 10.

[0027] 3A and 3B , in the vehicle bus bar 10 other than the present embodiment, the elongation percentage A (%) is greater than the percentage B (%). If the elongation percentage A (%) is greater than the percentage B (%), when the vehicle bus bar 10 is edgewise bent, the metal bar 20 is exposed.

[0028] (Method of Manufacturing an In-Vehicle Bus Bar) Next, a method of manufacturing the in-vehicle bus bar 10 will be described. Fig. 4 is a flowchart of the method of manufacturing the in-vehicle bus bar 10. Fig. 5A is a diagram for explaining the process of covering the metal bar 20, and Fig. 5B is a diagram for explaining the process of covering another metal bar 20.

[0029] As shown in FIG. 4, the method for manufacturing the vehicle bus bar 10 includes a step of coating the metal bar (S110) and a step of forming the straight portion and the bent portion (S120).

[0030] In the covering step (S110), insulating fire-resistant tape 30 is partially overlapped on metal bar 20 and wound laterally to cover metal bar 20. Next, metal bar 20 covered with insulating fire-resistant tape 30 is further covered with insulating layer 40.

[0031] In this case, when the outer circumferential length of the vehicle-mounted bus bar 10 at the bent portion 12 is L1, the central circumferential length of the vehicle-mounted bus bar 10 at the bent portion 12 is L2, the width of the insulating fire-resistant tape 30 is W1, and the overlap width of the insulating fire-resistant tape 30 in the region corresponding to the bent portion 12 before edgewise bending is W2, the metal bar 20 is covered with the insulating fire-resistant tape 30 so that the elongation percentage A (%) of the outer circumferential length L1 to the central circumferential length L2, as shown in the following formula (1), is smaller than the ratio B (%) of the overlap width W2 of the insulating fire-resistant tape to the width W1 of the insulating fire-resistant tape 30, as shown in the following formula (2). As shown in FIG. 5A , the metal bar 20 is covered with the insulating fire-resistant tape 30 so that a predetermined overlap width W2 is achieved with one wrap of the insulating fire-resistant tape 30. Formula (1) A = (L1 / L2 - 1) × 100 Formula (2) B = (W2 / W1) × 100

[0032] Alternatively, as shown in FIG. 5B, the first insulating fire-resistant tape 30 may be wound with a certain gap therebetween, and the second insulating fire-resistant tape 30 may be wound with a predetermined overlap width.

[0033] In the step (S120) of forming the straight portion and the bent portion, a portion is bent edgewise and flatwise, for example, to form the desired shape.

[0034] In addition, if the insulating layer 40 is not present, in the covering step (S110), the insulating fire-resistant tape 30 is partially overlapped on the metal bar 20 and wound horizontally to cover the metal bar 20, and the metal bar 20 is not covered with the insulating layer 40.

[0035] (Effect) As described above, according to the present invention, the elongation rate A (%) of the outer peripheral length L1 relative to the central peripheral length L2 is smaller than the ratio B (%) of the overlap width W2 of the insulating fire-resistant tape 30 relative to the width W1 of the insulating fire-resistant tape 30, so that fire resistance performance can be maintained.

[0036] The vehicle-mounted bus bar of the present invention is useful, for example, as a bus bar for electrically connecting between a vehicle-mounted battery and an inverter.

[0037] REFERENCE SIGNS LIST 10 Vehicle bus bar 11 Straight portion 12 Bent portion 13 First bent portion 14 Second bent portion 20 Metal bar 21 Hole 30 Insulating fireproof tape 31 Silicone tape layer 32 Glass tape layer 40 Insulator layer

Claims

1. An automotive busbar having a metal bar and insulating fire-resistant tape that is partially overlapping and laterally wound around the metal bar to cover the metal bar, the automotive busbar including straight portions and bent portions, wherein, when the outer periphery of the automotive busbar at the bent portion is L1, the central periphery of the automotive busbar at the bent portion is L2, the width of the insulating fire-resistant tape is W1, and the overlap width of the insulating fire-resistant tape at the straight portion is W2, an elongation rate A (%) of the outer periphery length L1 to the central periphery length L2, as shown in the following formula (1), is smaller than a ratio B (%) of the overlap width W2 of the insulating fire-resistant tape to the width W1 of the insulating fire-resistant tape, as shown in the following formula (2): Formula (1) A = (L1 / L2 - 1) x 100 Formula (2) B = (W2 / W1) x 100 2. An on-vehicle bus bar according to claim 1, wherein the insulating fire-resistant tape comprises a silicone tape layer made of silicone resin and a glass tape layer laminated on the silicone tape layer, and the glass tape layer is in contact with the metal bar.

3. An on-vehicle bus bar according to claim 1, wherein the insulating fire-resistant tape is a mica tape.

4. An on-vehicle bus bar according to claim 1 or 2, wherein the bent portion is bent edgewise.

5. A method for manufacturing an on-vehicle busbar, comprising the steps of: coating a metal bar by partially overlapping and laterally winding an insulating fire-resistant tape around the metal bar; and edgewise bending a portion of the metal bar coated with the insulating fire-resistant tape to form a straight portion and a bent portion, wherein, when the outer periphery of the on-vehicle busbar at the bent portion is L1, the central periphery of the on-vehicle busbar at the bent portion is L2, the width of the insulating fire-resistant tape is W1, and the overlap width of the insulating fire-resistant tape in a region corresponding to the bent portion before edgewise bending is W2, an elongation rate A (%) of the outer periphery length L1 to the central periphery length L2, as shown in the following formula (1), is smaller than a ratio B (%) of the overlap width W2 of the insulating fire-resistant tape to the width W1 of the insulating fire-resistant tape, as shown in the following formula (2): Formula (1): A = (L1 / L2 - 1) x 100 Formula (2): B = (W2 / W1) x 100

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