On-board bus bar and manufacturing method therefor

Abstract

The present invention discloses an on-board bus bar 1 that includes: a metal bar 10; fireproof tape; and an insulator layer 30. One or more layers of the fireproof tape are wound in an overlapping manner on the metal bar 10. The metal bar 10 and the fireproof tape are coated with the insulator layer 30.

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 the battery unit and the inverter. In recent years, electric vehicles have been equipped not only with motor drive, but also with electric brakes, steering, and even the opening and closing of doors and windows. Therefore, in the event of an emergency evacuation 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 electrical equipment running, ensuring evacuation and notification. Lithium-ion batteries are commonly used. Because these batteries can deform and catch fire due to external heating or self-heating, they are protected as a unit in a robust, fire-resistant container.

[0003] On the other hand, separate from the battery unit, the bus bar also needs to be fire-resistant. Patent Document 1 discloses a structure in which a bandage member (30A) is wrapped around a metal bar (10) and the outside of the bandage member is covered with an insulating tube (20). The bandage member is made of metal wire coated with a coating material (31) that has electrical insulation and fire resistance. In this structure, even if the insulating tube of the bus bar is lost in a fire, the bandage member remains attached to the metal bar, supporting the metal bar so that it does not come into contact with the surrounding metal structure (4), thereby preventing a short circuit (see paragraphs 0030-0036, 0047, Figures 3-4, and 7).

[0004] Special Publication No. 2022-545548

[0005] In an electric vehicle, if a fire breaks out due to an abnormality in or near the battery, the busbar will be exposed to high temperatures (e.g., approximately 900°C) immediately after the fire. As mentioned above, to keep electrical components running even in the event of a fire, the busbar must be able to maintain power supply for a certain period of time (e.g., 5 to 30 minutes) even at such high temperatures. However, with the structure of Patent Document 1, the polymer material constituting the insulating tube remains as charcoal in the event of a fire. Because charcoal is conductive, if the charcoal remains attached to the metal bar and comes into contact with surrounding metal structures, it will not prevent a short circuit. Therefore, a primary objective of the present invention is to provide a busbar and a method for manufacturing the same that can reliably prevent a short circuit caused by contact between the metal bar and surrounding metal structures.

[0006] In order to solve the above-mentioned problems, one aspect of the present invention provides an in-vehicle bus bar having a metal bar, a fire-resistant tape, and an insulating layer, wherein one or more layers of the fire-resistant tape are wound around the metal bar in an overlapping manner, and the metal bar and the fire-resistant tape are covered with the insulating layer.

[0007] According to another aspect of the present invention, there is provided a method for manufacturing an on-vehicle bus bar having a metal bar, a fire-resistant tape, and an insulating layer, the method comprising the steps of: winding one or more sheets of the fire-resistant tape around the metal bar in an overlapping manner; and extruding a predetermined resin onto the metal bar and the fire-resistant tape to coat them with the insulating layer.

[0008] According to the present invention, it is possible to reliably prevent a short circuit caused by contact between a metal bar and a surrounding metal structure.

[0009] FIG. 1 is a perspective view showing a schematic configuration of an in-vehicle bus bar. FIG. 2 is a cross-sectional view showing a schematic configuration of an in-vehicle bus bar. FIGS. 3A to 3E are exploded perspective views showing a schematic configuration of an in-vehicle bus bar. FIGS. 4A to 4D are exploded perspective views showing a schematic configuration of a modified in-vehicle bus bar. FIGS. 5A to 5C are exploded perspective views showing a schematic configuration of a modified in-vehicle bus bar. FIG. 6 is a perspective view for explaining a heat resistance test in the examples.

[0010] Hereinafter, busbars according to preferred embodiments of the present invention will be described. In this specification, the term "to" indicating a range of values ​​means that the range includes both the lower limit and the upper limit.

[0011] 1 and 2, an automotive bus bar 1 is mainly composed of a metal bar 10, a fire-resistant tape 20, and an insulating layer 30. One or more layers of fire-resistant tape 20 are overlap-wound around the metal bar 10, and these are covered with an insulating layer 30. "Overlap winding" includes both so-called longitudinal and transverse winding (see below).

[0012] The metal bar 10 is typically made of a single metal plate, with its thickness and width determined by the magnitude of the current flowing through it, and various lengths are available depending on the installation location or conditions. The metal bar 10 may also be made by laminating multiple thin metal plates. For example, the metal bar 10 may be made by laminating thin metal plates of approximately 0.1 to 0.3 mm and welding both ends together, thereby providing a flexible structure that can be twisted and bent. The metal plate or thin metal plate of the metal bar 10 is preferably made of copper or a copper alloy.

[0013] One end of the metal bar 10 is connected to the positive terminal of one battery, and the other end is connected to the negative terminal of the other battery. For example, if the battery terminals are bolt-type, the holes 12 at both ends of the metal bar 10 can be fitted to the terminals and fastened with nuts to firmly secure the connection between the battery and the vehicle bus bar 1 (metal bar 10).

[0014] The fire-resistant tape 20 is made of mica tape, which exhibits insulating properties at high temperatures. Mica is a natural mineral (called mica in Japanese) with excellent electrical insulation and heat resistance. While mica itself is a mineral, when made into tape, it has good flexibility, making it suitable for curving or bending. The mica tape may be glass mica tape, in which mica is bonded to glass cloth, or plastic mica tape, in which mica is bonded to a plastic film made of polyethylene or the like.

[0015] As shown in Fig. 3A, the fire-resistant tape 20 is longitudinally wrapped around the metal bar 10. "Longitudinal wrapping" means that a long tape is arranged along the length of the object to be wrapped and wrapped around the object in a cylindrical shape so that both side edges are wrapped inward. As shown in Fig. 3B, a glass yarn 22 may be wound on top of the fire-resistant tape 20 longitudinally wrapped around the metal bar 10. In other words, the glass yarn 22 may be loosely wound and pressed down. Instead of the glass yarn 22, as shown in FIG. 3C, a polyethylene terephthalate (PET) tape 24 may be wound around the fire-resistant tape 20 with a certain gap therebetween and fixed, or as shown in FIG. 3D, an adhesive tape 26a may be applied along the surface of the side edge of the fire-resistant tape 20 to fix the fire-resistant tape 20, or as shown in FIG. 3E, an adhesive 26b may be applied to the back surface of the side edge of the fire-resistant tape 20, or an adhesive tape 26a may be applied to fix the fire-resistant tape 20.

[0016] The insulating layer 30 is formed by extruding a certain resin from the die of an extruder. The resin is preferably a flame-retardant resin, such as polyamide (PA; PolyAmide), polyvinyl chloride (PVC; PolyVinyl Chloride), polyethylene (PE; PolyEthylene), or polypropylene (PP; PolyPropylene).

[0017] Next, a method for manufacturing the vehicle-mounted bus bar 1 will be described.

[0018] First, one piece of fire-resistant tape 20 is wrapped lengthwise on the metal bar 10. If necessary, the fire-resistant tape 20 may be fixed by, for example, pressing it with glass yarn 22. Then, a certain resin is extruded onto the outside of the fire-resistant tape 20 to form an insulating layer 30, thereby forming a precursor of the vehicle-mounted busbar 1. Finally, the precursor is curved or bent depending on the installation location or conditions, thereby manufacturing (finishing) the vehicle-mounted busbar 1.

[0019] According to the above-described vehicle-mounted busbar 1, the fire-resistant tape 20 is directly wrapped around the metal bar 10. Therefore, even if a fire occurs due to an accident or poor maintenance and the insulator layer 30 turns into carbide and remains, the remaining carbide does not adhere to the metal bar 10, preventing it from coming into contact with surrounding metal structures and causing a short circuit. Furthermore, according to the vehicle-mounted busbar 1, the fire-resistant tape 20 contains mica, giving it a certain degree of flexibility. Therefore, when the precursor of the vehicle-mounted busbar 1 is curved or bent, the fire-resistant tape 20 follows the curve or bend without creating a gap between itself and the metal bar 10. In this case, as with the above, even if a fire occurs due to an accident or poor maintenance and the insulator layer 30 turns into carbide and remains, the remaining carbide does not adhere to the metal bar 10, preventing it from coming into contact with surrounding metal structures and causing a short circuit.

[0020] As described above, the vehicle-mounted bus bar 1 can reliably prevent short circuits caused by contact between the metal bar 10 and surrounding metal structures.

[0021] The overlapping and winding manner of the fire-resistant tape 20 of the vehicle-mounted bus bar 1 is not limited to the structures shown in FIGS. 3A to 3E, and the number of layers and the winding manner may be changed as appropriate.

[0022] For example, as shown in Figures 4A to 4C, two pieces of fire-resistant tape 20 may be prepared and wrapped longitudinally around the metal bar 10, overlapping each other. In such cases, it is preferable to wrap the first and second fire-resistant tapes 20 longitudinally so that their side edges are inverted vertically or horizontally. As shown in Figure 4B, a polypropylene yarn 28 may be wound around the first fire-resistant tape 20, and a glass yarn 22 may be wound around the second fire-resistant tape 20, and the fire-resistant tapes 20 may be secured together. As shown in Figure 4C, a PET tape 24 may be wound around the second fire-resistant tape 20 with a certain gap between them to secure them together. As shown in Figure 4D, two pieces of fire-resistant tape 20 may be prepared, with the first fire-resistant tape 20 wrapped longitudinally around the metal bar 10 and the second fire-resistant tape 20 wrapped transversely around the first fire-resistant tape 20. "Horizontal winding" means winding a long tape spirally along the length of the object to be wound, with the side edge of the tape overlapping the previously wound tape.

[0023] As shown in Fig. 5A, one piece of fire-resistant tape 20 may be prepared and wrapped laterally around the metal bar 10. As shown in Fig. 5B, two pieces of fire-resistant tape 20 may be prepared, with the first piece of fire-resistant tape 20 wrapped around the metal bar 10 with a certain gap between them, and the second piece of fire-resistant tape 20 wrapped along the gap. As shown in Fig. 5C, two pieces of fire-resistant tape 20 may be prepared, with the first piece of fire-resistant tape 20 wrapped laterally around the metal bar 10, and the second piece of fire-resistant tape 20 wrapped laterally on top of that.

[0024] The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples.

[0025] 1. Fabrication of Bus Bars (1) Bus Bar of Example 1 A single mica tape (Glory Mica Co., Ltd.) with a mica layer thickness of 0.025 mm and a width of 12 mm was wrapped transversely around the center (150 mm) of a 250 mm long copper metal bar (see FIG. 5A). The mica tape was wrapped so that half of the width of the mica tape overlapped the previously wrapped mica tape. Therefore, the total thickness (calculated value) of the mica layer at the center of the metal bar was 0.05 mm. Next, an insulating layer made of polyolefin resin was formed on the mica tape.

[0026] (2) Busbar of Example 2 A single mica tape (Nippon Rika Kogyosho Co., Ltd.) with a mica layer thickness of 0.035 mm and a width of 16 mm was wrapped transversely around the center of a metal bar similar to the busbar of Example 1 (see FIG. 5A ). The mica tape was wrapped so that half of the width of the mica tape overlapped the previously wrapped mica tape. Therefore, the total thickness (calculated value) of the mica layer in the center of the metal bar was 0.07 mm. Next, as with the busbar of Example 1, an insulating layer made of polyolefin resin was formed on the mica tape.

[0027] (3) Busbar of Example 3 Two mica tapes (Nippon Rika Kogyosho Co., Ltd.) with a mica layer thickness of 0.035 mm and a width of 16 mm were wrapped transversely around the center of a metal bar similar to the busbar of Example 1 (see FIG. 5C ). Each mica tape was wrapped so that half of the width of the mica tape overlapped the previously wrapped mica tape. Therefore, the total thickness (calculated value) of the mica layer at the center of the metal bar was 0.14 mm. Next, as with the busbar of Example 1, an insulating layer made of polyolefin resin was formed on the mica tape.

[0028] (4) Busbar of Example 4 A piece of mica tape (Okabe Mica Industries Co., Ltd.) with a mica layer thickness of 0.12 mm and a width of 50 mm was wrapped longitudinally around the center of a metal bar similar to the busbar of Example 1 (see FIG. 3A ). The total thickness (calculated value) of the mica layer in the center of the metal bar was 0.12 mm. Next, as with the busbar of Example 1, an insulating layer made of polyolefin resin was formed on the mica tape.

[0029] (5) Busbar of Example 5 A single mica tape (Okabe Mica Industries Co., Ltd.) with a mica layer thickness of 0.12 mm and a width of 50 mm was wrapped transversely around the center of a metal bar similar to the busbar of Example 1 (see FIG. 5A ). The mica tape was wrapped so that half of the width of the mica tape overlapped the previously wrapped mica tape. Therefore, the total thickness (calculated value) of the mica layer in the center of the metal bar was 0.24 mm. Next, as with the busbar of Example 1, an insulating layer made of polyolefin resin was formed on the mica tape.

[0030] (6) Busbar of Example 6 Two pieces of mica tape (Okabe Mica Industries Co., Ltd.), each with a mica layer thickness of 0.12 mm and a width of 50 mm, were wrapped longitudinally around the center of a metal bar similar to the busbar of Example 1 (see FIG. 4A ). The total thickness (calculated value) of the mica layer at the center of the metal bar was 0.24 mm. Next, as with the busbar of Example 1, an insulating layer made of polyolefin resin was formed on the mica tape.

[0031] (7) Busbar of Comparative Example 1 An insulating layer made of polyolefin resin was formed in the center of a metal bar similar to the busbar of Example 1, without wrapping it with mica tape.

[0032] (8) Busbar of Comparative Example 2 A piece of mica tape (Nippon Rika Kogyosho Co., Ltd.) with a mica layer thickness of 0.035 mm and a width of 16 mm was wound around the center of a metal bar similar to the busbar of Example 1, with a certain gap between them (gap winding, not lap winding) (see the first fire-resistant tape 20 in FIG. 5B ). Next, as with the busbar of Example 1, an insulating layer made of polyolefin resin was formed on the mica tape.

[0033] 2. Evaluation of Bus Bars The insulation resistance of each of the manufactured bus bars at the center where the insulator layer was formed was measured before and after the heat resistance test.

[0034] The heat resistance test was performed by heating the bus bar 1 in a heating furnace with a 2 kg weight 44 suspended from the center (where the insulator layer 30 was formed) of the bus bar 1 supported by two support bases 40 using two 2 mm diameter wires 42, as shown in FIG. 6 . The heating temperature (air temperature in the heating furnace) was 500°C, 700°C, or 900°C. The heating time (holding time after reaching the above temperature) was 30 minutes. In all bus bars, the insulator layer was completely carbonized by heating at 500°C for 30 minutes, and completely disappeared by heating at 700°C for 30 minutes.

[0035] The insulation resistance was measured using a super insulation resistance meter (SM-8220, Hioki E.E. Corporation). The insulation resistance of each bus bar before the heat resistance test was 1 × 10 ７ The heat resistance of each bus bar was evaluated as follows: Good: Insulation resistance after heat resistance test was 0.4 MΩ or more; Bad: Insulation resistance after heat resistance test was less than 0.4 MΩ.

[0036] Table 1 shows the insulation resistance values ​​and evaluation results of each bus bar before and after the heat resistance test.

[0037] In the bus bar of Comparative Example 1, which was not wrapped with fire-resistant tape (mica tape), after heating at 500°C for 30 minutes, carbide from the insulator layer remained around the metal bar. However, because this carbide was conductive, the insulation resistance was very low. Furthermore, after heating at 700°C for 30 minutes or 900°C for 30 minutes, the insulator layer was completely burned away, making it impossible to measure the insulation resistance.

[0038] Even in the case of the busbar of Comparative Example 2, in which the fire-resistant tape was wrapped with a certain gap, the gaps in the fire-resistant tape were in the same state as the busbar of Comparative Example 1, so the insulation resistance was either very low or could not be measured.

[0039] On the other hand, in the bus bars of Examples 1 to 6 in which the fire-resistant tape was overlap-wrapped, the insulation resistance was high even after heating at 900°C for 30 minutes, because the fire-resistant tape was present without any gaps around the metal bar.

[0040] From the above results, it can be seen that the bus bar according to the present invention can maintain power supply for a certain period of time (for example, 30 minutes) even when exposed to a high temperature of, for example, 900°C.

[0041] This application claims priority based on Japanese Patent Application No. 2023-106948, filed June 29, 2023. The contents of the specification and drawings of that application are incorporated herein by reference in their entirety.

[0042] The present invention relates to an on-vehicle bus bar and a manufacturing method thereof, and is particularly useful for providing a bus bar that can reliably prevent short circuits caused by contact between the metal bar and surrounding metal structures.

[0043] REFERENCE SIGNS LIST 1 Vehicle bus bar 10 Metal bar 12 Hole 20 Fireproof tape 22 Glass yarn 24 PET tape 26a Adhesive tape 26b Adhesive 28 Polypropylene yarn 30 Insulator layer 40 Support base 42 Wire 44 Weight

Claims

1. A metal bar made of a single metal plate, Two or more fire-resistant tapes are wrapped around the aforementioned metal bar, The metal bar and the two or more fire-resistant tapes are covered by an insulating layer, The metal bar has two or more pieces of fire-resistant tape wrapped horizontally around it. An in-vehicle bus bar characterized in that, of the two or more fire-resistant tapes that are wound horizontally, the first fire-resistant tape is wound around the metal bar with a first gap, and the second fire-resistant tape is wound around the metal bar along the first gap with a second gap.

2. A step of wrapping two or more fire-resistant tapes in layers around a metal bar made of a single metal plate, A step of extruding a certain amount of resin onto the metal bar and the two or more fire-resistant tapes to cover them with an insulating layer, Equipped with, In the process of wrapping two or more fire-resistant tapes in layers, the two or more fire-resistant tapes are wrapped horizontally around the metal bar. A method for manufacturing a vehicle-mounted bus bar, characterized in that, when wrapping the two or more fire-resistant tapes horizontally around the metal bar, the first fire-resistant tape is wrapped around the metal bar with a first gap, and then the second fire-resistant tape is wrapped around the metal bar along the first gap with a second gap.