On-board bus bar

Abstract

The purpose of the present invention is to provide an on-board bus bar which maintains fire resistance performance and insulation performance even if a fire or the like occurs over a long period of time. To this end, provided is an on-board bus bar (10) comprising: a metal bar (20); a fire-resistant layer (30) that covers the metal bar (20); and an insulator layer (40) that covers the fire-resistant layer (30) and contains a resin. The insulator layer (40) has a melt viscosity at 260°C of 1000 Pa·s or more.

Description

Automotive Bus Bars

[0001] The present invention relates to a bus bar suitable for in-vehicle use.

[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 wheel, doors, and window opening and closing mechanisms are electrically operated. Therefore, if a vehicle needs to leave the vehicle due to an accident or a fire caused by poor maintenance, the power supply system, including the battery unit and bus bars, must be able 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, can deform and ignite due to external heating or self-heating. Therefore, lithium-ion batteries are protected as a unit in a robust, fire-resistant container. Furthermore, bus bars must be efficiently routed in the limited space around the battery, and therefore must also 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 made of a heat-shrinkable material such as polyolefin, polyvinyl chloride, or fluorine-based resin. The busbar wire is formed by placing the flat conductor inside the insulating coating and then thermally shrinking the insulating coating with a heat gun, iron, or the like.

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

[0005] However, in the busbar wire of Patent Document 1, if a fire caused by an accident or poor maintenance occurs over a long period of time, the insulating coating may melt due to heat. If the molten coating falls from the busbar wire, there is a risk of secondary fire spread. Furthermore, if the insulating layer burns and carbonizes, the insulating performance of the insulating layer may deteriorate, which may further exacerbate the damage.

[0006] Therefore, a main object of the present invention is to provide an in-vehicle bus bar that can maintain fire resistance and insulating performance even in the event of a fire or the like that lasts for a long period of time.

[0007] In order to solve the above problems, one aspect of the present invention provides the following on-board bus bar: [1] An on-board bus bar comprising: a metal bar; a fire-resistant layer covering the metal bar; and an insulator layer covering the fire-resistant layer and containing a resin, wherein the insulator layer has a melt viscosity of 1000 Pa s or more at 260°C. [2] An on-board bus bar comprising: a metal bar; a fire-resistant layer covering the metal bar; and an insulator layer covering the fire-resistant layer and containing a resin, wherein the insulator layer has a melt viscosity of 20 kgf / cm at 260°C. ２ [3] An automotive busbar having a melt flow rate under load of 50 g / 10 min or less. [4] The automotive busbar according to [1] or [2] above, wherein the insulator layer has a flash point of 370°C or higher as determined by the following method. (Method for determining flash point) (i) 3 g of the insulator layer is taken and placed in a combustion boat. (ii) The combustion boat is heated to a temperature of 1000°C (air flow rate: 6.75 / min) and a furnace pressure of 0.5 kgf / cm. ２ (iii) Visually check the state of the combustion boat introduced into the furnace until 13 minutes have passed since the temperature of the combustion boat introduced into the furnace reaches the test temperature, and confirm whether ignition occurs. (iv) Repeat steps (i) to (iii) by changing the temperature inside the vertical furnace, and determine the lowest temperature at which ignition occurs within 13 minutes as the flash point.

[0008] According to the present invention, it is possible to provide an in-vehicle bus bar that can maintain fire resistance and insulation performance even in the event of a fire or the like occurring for a long period of time.

[0009] Fig. 1A is a perspective view showing the configuration of an automotive busbar according to one embodiment of the present invention, and Fig. 1B is a cross-sectional view taken along line A-A in Fig. 1A. Fig. 2 is a flowchart showing a method for manufacturing an automotive busbar according to one embodiment of the present invention. Fig. 3 is a graph showing the results of measuring the melt viscosity of the insulator layer of an automotive busbar produced in an example. Fig. 4 is a graph showing the results of measuring the melt flow rate of the insulator layer of an automotive busbar produced in an example.

[0010] 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.

[0011] FIG. 1A is a perspective view showing the configuration of an automotive busbar 10 according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view. As shown in FIGS. 1A and 1B, the automotive busbar 10 of this embodiment includes a metal bar 20, a fire-resistant layer 30 covering the metal bar 20, and an insulating layer 40 covering the fire-resistant layer 30. The insulating layer 40 of a conventional automotive busbar 10 having this configuration has traditionally been made of heat-shrinkable materials such as polyolefin, polyvinyl chloride, fluorine-based resin, and silicone. However, insulating layers 40 made of these resins tend to melt and become more fluid when heated to high temperatures in the event of a fire or other incident. The molten resin may then fall onto the surrounding area, potentially causing secondary fire spread. On the other hand, if the molten resin penetrates into gaps in the fire-resistant layer 30, it may burn or carbonize. As a result, even if the insulating layer 40 and fire-resistant layer 30 are included, there is a concern that the insulating performance may be reduced, further exacerbating the damage.

[0012] In contrast, the insulator layer 40 of the vehicle-mounted busbar 10 of this embodiment satisfies at least one of the following conditions (a) and (b). It is preferable that the insulator layer 40 further satisfies the following condition (c): (a) the melt viscosity of the insulator layer 40 at 260°C is 1000 Pa·s or more; (b) the melt viscosity of the insulator layer 40 at 260°C is 20 kgf / cm ２(c) The insulating layer 40 has a flash point of 370°C or higher, as determined by a verification method described below.

[0013] Both conditions (a) and (b) mean that the molten material of the insulator layer 40 has low fluidity. In other words, if the insulator layer 40 satisfies either of these conditions (a) or (b), even if a fire or the like occurs, the molten material of the insulator layer 40 is unlikely to fall off the vehicle bus bar 10 or penetrate into gaps in the fire-resistant layer 30. The vehicle bus bar 10 having such an insulating layer 40 can maintain its fire resistance and insulating performance for a long period of time, even if a fire or the like occurs. Each of the above conditions will be described in detail.

[0014] Regarding condition (a), the melt viscosity of the insulator layer 40 at 260°C is a value obtained by separating the insulator layer 40 from the vehicle bus bar 10 and measuring the melt viscosity of the insulator layer 40 alone at 260°C using a constant test force extrusion capillary rheometer flow tester (manufactured by Shimadzu Corporation). The melt viscosity of the insulator layer 40 at 260°C is more preferably 1,000 Pa·s or more. If the melt viscosity of the insulator layer 40 at 260°C is excessively high, it tends to be difficult to form the insulator layer 40. Therefore, from the viewpoint of ease of formation of the insulator layer 40, the melt viscosity of the insulator layer 40 at 260°C is preferably 350,000 Pa·s or less.

[0015] Regarding the condition (b), the MFR of the insulator layer 40 at 260°C is 20 kgf / cm when the insulator layer 40 is separated from the vehicle-mounted bus bar 10 and the MFR of the insulator layer 40 alone is 20 kgf / cm at 260°C. ２ The MFR under the load is determined using an MFR measuring device. ２ The MFR under load is more preferably 50 g / 10 min or less. If the MFR of the insulator layer 40 at 260°C is too low, it tends to be difficult to form the insulator layer 40. Therefore, from the viewpoint of ease of forming the insulator layer 40, the MFR of the insulator layer 40 at 260°C is preferably 0.05 g / 10 min or more.

[0016] Regarding condition (c), if the flash point of the insulator layer 40 is 370°C or higher, the insulator layer is difficult to ignite, and even if a fire occurs over a long period of time, it can be said that the fire resistance performance is very good. The flash point of the insulator layer 40 is determined by the following confirmation method. (Method for Confirming Flash Point) (i) 3 g of the insulator layer alone is taken and placed in a combustion boat. (ii) The combustion boat is placed in a furnace with an air flow rate of 6.75 / min and a furnace pressure of 0.5 kgf / cm. ２ The sample is introduced into a vertical furnace with an inner diameter of 70 mm, and the furnace temperature is adjusted to the test temperature. (iii) The state of the combustion boat introduced into the furnace is visually confirmed for 13 minutes after the temperature reaches the test temperature, to confirm whether ignition occurs. (iv) The furnace temperature is changed and steps (i) to (iii) are repeated to identify the temperature at which ignition occurs within 13 minutes, and the lowest temperature at which ignition occurs is taken as the flash point. The flash point may be 370°C or higher, and more preferably 380°C or higher. However, the higher the flash point, the better, so there is no particular upper limit.

[0017] (Configuration of the Vehicle Bus Bar) The configuration of the vehicle bus bar will be described in detail below. The metal bar 20 included in the vehicle bus bar 10 of this embodiment 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 conductive. 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 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, and the like. When the metal bar 20 is made of multiple stacked thin metal plates, the thickness of the metal plate is within a 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, allowing it to be twisted or bent. 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.

[0018] The fire-resistant layer 30 is a layer disposed to cover the metal bar 20 except for the connection portion with the terminal. The fire-resistant layer 30 is, for example, composed of insulating fire-resistant tape wound horizontally to cover the metal bar 20. The insulating fire-resistant tape need only have insulating properties and may be composed of one layer or two layers. Examples of insulating fire-resistant tapes include mica tape and silicone tape. The mica (also called "mica") contained in mica tape is a natural mineral that has excellent electrical insulation and heat resistance. The mica tape may be a glass-mica tape in which mica is bonded to glass cloth. Alternatively, the mica tape may be a plastic-mica tape in which mica is bonded to a plastic film such as polyethylene. On the other hand, the silicone tape may be a tape composed of a single layer of silicone, or a tape composed of a laminate of a layer of silicone and a layer of glass cloth made of flat-woven glass fiber. If the insulating fire-resistant tape includes a glass cloth layer, the glass cloth layer is preferably disposed on the metal bar 20 side. The thickness of the fire-resistant layer 30 is preferably within a range of 0.1 to 0.5 mm. When the thickness of the fire-resistant layer 30 is 0.1 mm or more, the fire resistance and insulating properties are likely to be good. On the other hand, when the thickness of the fire-resistant layer 30 is 0.5 mm or less, the thickness of the fire-resistant layer is unlikely to be excessively thick.

[0019] The insulator layer 40 is a layer disposed to cover the fire-resistant layer 30 and contains a resin. The material of the insulator layer 40 is not particularly limited as long as it satisfies the above-mentioned condition (a) or (b). Materials for the insulator layer 40 that can satisfy the above-mentioned condition (a) or (b) include dynamically crosslinked polyolefin resins and rubber components. When the insulator layer 40 contains such dynamically crosslinked materials, the dynamically crosslinked portions tend to suppress the fluidity of the molten insulator layer 40 and further increase the flash point. Here, the dynamically crosslinked polyolefin resin and rubber component refers to a material in which a polyolefin resin and a rubber component are crosslinked by applying a shear force in the presence of a crosslinking agent. The dynamic crosslinking can be performed during compound preparation or when the insulator layer 40 is formed by extrusion molding or the like.

[0020] The polyolefin resin used as the material for the dynamically crosslinked product may be any resin primarily containing olefin-derived structures. Specifically, the polyolefin resin may contain olefin-derived structural units in an amount of 50% by mass or more, preferably 80% by mass or more, of the total structural units constituting the polyolefin resin. Examples of polyolefin resins include olefin homopolymers, copolymers of two or more olefins, and copolymers of olefins with monomers other than olefins. The olefin preferably has 2 to 20 carbon atoms. Specific examples of olefins include ethylene, propylene, butylene, 1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene. Examples of non-olefin monomers copolymerizable with olefins include vinyl acetate, methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate. In this specification, the term "(meth)acrylate" includes methacrylate, acrylate, and mixtures thereof. Specific examples of polyolefin resins include polyethylene (ultra-low density polyethylene, low density polyethylene, high density polyethylene, etc.), polypropylene, polybutylene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, ethylene-butylene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, ethylene-butylene-hexene copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl (meth)acrylate copolymer, ethylene-ethyl (meth)acrylate copolymer, ethylene-butyl (meth)acrylate copolymer, etc. These can be used alone or in combination of two or more. Among the above, it is preferable that the polyolefin resin contains a structural unit derived from propylene, and polypropylene is preferred.

[0021] Examples of the rubber component include diene rubbers such as natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), butadiene rubber (BR), and acrylonitrile butadiene rubber (NBR), as well as hydrogenated products thereof; olefin rubbers such as ethylene propylene rubber (EPDM, EPM) and butyl rubber (IIR); acrylic rubber (ACM); halogen-containing rubbers such as brominated butyl rubber, chlorinated butyl rubber, and halogenated isoolefin-para-alkylstyrene copolymer; silicone rubbers such as methyl vinyl silicone rubber and dimethyl silicone rubber; sulfur-containing rubbers such as polysulfide rubber; fluorine-containing rubbers such as vinylidene fluoride rubber and fluorine-containing vinyl ether rubber; and thermoplastic elastomers such as styrene elastomers, olefin elastomers, acid-modified olefin elastomers, ester elastomers, urethane elastomers, and polyamide elastomers. These may be used alone or in combination of two or more. Of the above, the rubber component is preferably an olefin-based elastomer or a styrene-based elastomer, and more preferably a styrene-based elastomer.

[0022] The crosslinking agent for dynamically crosslinking the polyolefin resin and the rubber component is not particularly limited, and examples thereof include sulfur, phenolic resins such as phenol-formaldehyde resins, peroxides, etc. Among these, peroxides are preferred in terms of reactivity, etc. Specific examples of peroxides include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl perbenzoate, tert-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, tert-butylcumyl peroxide, etc. These may be used alone or in combination of two or more.

[0023] When obtaining a dynamically crosslinked product, the amount of rubber component is preferably 15 to 40 parts by mass, more preferably 17.5 to 37.5 parts by mass, per 100 parts by mass of polyolefin resin. By adjusting the mass ratio of polyolefin resin to rubber component within this range, it becomes easier to satisfy the above gel fraction. In addition, the amount of crosslinking agent is preferably 0.1 to 0.5 parts by mass per 100 parts by mass of the polyolefin resin and rubber component combined. Within this range, dynamic crosslinking easily proceeds efficiently, and the gel fraction is easily increased.

[0024] Preferably, the insulator layer 40 further contains a flame retardant. When the insulator layer 40 contains a flame retardant, the flame retardancy of the insulator layer 40 is enhanced. The insulator layer 40 may contain only one type of flame retardant, or may contain two or more types of flame retardants. Examples of flame retardants include magnesium hydroxide, aluminum hydroxide, halogen-based flame retardants, and phosphorus-based flame retardants. Among these, magnesium hydroxide is preferred from the viewpoint of ease of handling, etc. When the insulator layer 40 contains a flame retardant, the amount of the flame retardant in the insulator layer 40 is preferably 30% by mass or more and 60% by mass or less, and more preferably 35% by mass or more and 55% by mass or less, relative to the total amount of the dynamically crosslinked product and the flame retardant.

[0025] The insulator layer 40 may further contain a copper inhibitor. When the metal bar 20 is made of copper or a copper alloy, copper ions from the metal bar 20 may deteriorate the insulator layer 40 (particularly the dynamically cross-linked product), resulting in a decrease in insulating performance. In contrast, when the insulator layer 40 contains a copper inhibitor, such a decrease in insulating performance is more easily suppressed. The insulator layer 40 may contain only one type of copper inhibitor, or may contain two or more types. The copper inhibitor may be any compound capable of capturing copper ions. Examples of copper inhibitors include hydrazides such as N'1,N'12-bis(2-hydroxybenzoyl)dodecane dihydrazide, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, and isophthalic acid bis(2-phenoxypropionylhydrazine); 2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzoamide; alcohol carboxylic acid esters, etc. When the insulator layer 40 contains a copper inhibitor, the amount of the copper inhibitor in the insulator layer 40 is, from the viewpoint of copper inhibition, preferably 0.1 parts by mass or more and 0.5 parts by mass or less, and more preferably 0.2 parts by mass or more and 0.4 parts by mass or less, relative to 100 parts by mass of the total amount of the dynamically crosslinked product and the flame retardant.

[0026] In addition to the dynamically crosslinked material, flame retardant, and copper inhibitor described above, the insulator layer 40 may further contain known additives, fillers, etc., within the scope that does not impair the purpose and effects of this embodiment.

[0027] (Method of Manufacturing an On-Vehicle Busbar) Next, a method of manufacturing the on-vehicle busbar 10 will be described. Fig. 2 is a flowchart of the method of manufacturing the on-vehicle busbar 10. As shown in Fig. 2, the method of manufacturing the on-vehicle busbar 10 includes a step (S110) of preparing a metal bar 20, a step (S120) of forming a fire-resistant layer 30 so as to cover the metal bar 20, and a step (S130) of forming an insulator layer 40 so as to cover the fire-resistant layer 30.

[0028] In the step (S110) of preparing a metal bar 20, a metal bar 20 is prepared. The metal bar 20 may be a commercially available product or may be manufactured.

[0029] In the step (S120) of forming the fire-resistant layer 30 of this embodiment, the fire-resistant tape is wound horizontally with a partial overlap to cover the metal bar 20. At this time, two pieces of insulating fire-resistant tape may be wound. For example, the first piece of insulating fire-resistant tape may be wound horizontally with a certain gap between them. Then, the second piece of insulating fire-resistant tape may be further wound horizontally with a predetermined overlap width over the first piece of insulating fire-resistant tape.

[0030] In the step (S120) of forming the insulator layer 40, the insulator layer 40 is formed so as to cover the fire-resistant layer 30. In this step, a resin composition containing the above-mentioned raw materials for the dynamically cross-linked product (a polyolefin resin, a rubber component, and a cross-linking agent), as well as a flame retardant, a copper inhibitor, and the like, as needed, is prepared. The resin composition is then melt-kneaded and extruded around the fire-resistant layer 30 to form the above-mentioned insulator layer 40.

[0031] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited by these examples, and the embodiments can be modified without departing from the spirit of the present invention.

[0032] 1. Preparation of an automotive bus bar (1) Example 1 A metal bar (width 20 to 30 mm × thickness 3 to 5 mm) made of rectangular copper was prepared. Two mica tapes (MAT-1PM18W, manufactured by Okabe Mica Industries Co., Ltd.) were wrapped horizontally around the metal bar with half of each tape overlapping, forming a fire-resistant layer.

[0033] As shown in Table 1 below, 100 parts by mass of polypropylene, which is the material for the dynamically crosslinked product, 37.5 parts by mass of a rubber component (styrene-based elastomer), and 0.3 parts by mass of a crosslinking agent (peroxide crosslinking agent), were charged into a kneading extruder. Furthermore, each component was further charged into the kneading extruder so that the amounts of the resulting dynamically crosslinked product and the flame retardant (magnesium hydroxide) would be the compositions shown in Table 2 below. The resin composition was then melt-kneaded and extruded around the fire-resistant layer to form an insulating layer. The insulating layer had a thickness of 1 mm.

[0034] (2) Examples 2 to 5 and Comparative Examples 1 and 2 Automotive bus bars were obtained in the same manner as in Example 1, except that the material of the dynamically cross-linked product was changed as shown in Table 1 below, and the composition of the insulator layer was changed as shown in Table 2 below. Irganox MD 1024 (manufactured by BASF) was used as the copper damage inhibitor. In Comparative Example 2, polyamide was used as the resin, and dynamic cross-linking was not performed.

[0035] 2. Physical Property Measurement and Evaluation (1) Measurement of Melt Viscosity (260°C) The insulator layers were peeled off from the automotive bus bars produced in the Examples and Comparative Examples. The melt viscosities of the insulator layers at 150°C to 280°C were measured using a constant test force extrusion-type capillary rheometer flow tester (manufactured by Shimadzu Corporation). The melt viscosity at 260°C was determined from the measured values. Each insulator layer was measured three times. The results are shown in Figure 3, and the average values ​​of the three measurements are shown in Table 2. In Figure 3, the solid line is the approximate curve for Comparative Example 1, and the dotted line is the approximate curve for Example 4.

[0036] (2) Measurement of MFR (260°C) The insulator layers were peeled off from the automotive bus bars produced in the Examples and Comparative Examples. The MFR of the insulator layers at 150°C to 280°C was measured using an MFR measuring device. The MFR at 260°C was determined from the measured values. The measurements were carried out three times for each insulator layer. The results are shown in Figure 4, and the average values ​​of the three measurements are shown in Table 2.

[0037] (3) Identification of Flash Point The insulator layer was peeled off from the vehicle bus bars produced in the Examples and Comparative Examples. Then, the flash point was identified by the following method. The results are shown in Table 2. (i) 3 g of the insulator layer was taken and placed in a combustion boat. (ii) The combustion boat was placed in a furnace with an air flow rate of 6.75 / min and a furnace pressure of 0.5 kgf / cm. ２ (iii) The combustion boat introduced into the furnace was visually inspected for 13 minutes after the temperature reached the test temperature to determine whether ignition occurred. (iv) The furnace temperature was changed and the above steps (i) to (iii) were repeated to determine the temperature at which ignition occurred within 13 minutes. The lowest temperature at which ignition occurred was designated as the flash point.

[0038] (4) Measurement of Minimum Insulation Resistance at 500°C The insulation resistance of the insulator layer of the vehicle-mounted bus bars produced in the Examples and Comparative Examples was measured by the following method. First, the vehicle-mounted bus bars produced in the Examples and Comparative Examples were placed inside a heating furnace, and a load of 1 kg or more was applied to the vehicle-mounted bus bars. The vehicle-mounted bus bars were then preheated until the internal temperature reached 500°C. Next, the vehicle-mounted bus bars were subjected to main heating at 500°C for 30 minutes. During the main heating, specifically, immediately after the start of the main heating, and after 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, and 30 minutes, the insulation resistance was measured using a mega tester. The minimum insulation resistance during the 30-minute heating at 500°C was evaluated according to the following criteria. The results are shown in Table 2. ◯: Minimum insulation resistance at 500°C is 1 MΩ or more. ×: Minimum insulation resistance at 500°C is less than 1 MΩ or burnt.

[0039] (5) Evaluation of Drooping The presence or absence of drooping of the insulator layer was evaluated as follows. It was visually evaluated whether the insulator layer melted and fell off due to heating during the measurement of the insulation resistance value. Drooping was evaluated according to the following criteria. The results are shown in Table 2. ◯: The molten insulator layer did not fall off. ×: The molten insulator layer fell off.

[0040] 3. result

[0041]

[0042] As shown in Table 2, the insulator layers of Examples 1 to 4 have a melt viscosity of 1000 Pa·s or more at 260°C and a compressive strength of 20 kgf / cm at 260°C. ２ The MFR under load was 50 g / 10 min or less. The automotive bus bars having the insulator layers of Examples 1 to 4 had high insulation resistance when heated at 500°C and also had a good sagging evaluation. In contrast, Comparative Example 1, which did not satisfy the above melt viscosity and MFR values, had low insulation resistance when heated at 500°C and also had a poor sagging evaluation.

[0043] 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.

[0044] 10: Vehicle bus bar 20: Metal bar 30: Fire-resistant layer 40: Insulator layer

Claims

1. An automotive bus bar comprising: a metal bar; a fire-resistant layer covering the metal bar; and an insulating layer covering the fire-resistant layer and containing a resin, wherein the insulating layer has a melt viscosity of 1000 Pa·s or more at 260°C.

2. An automotive bus bar comprising: a metal bar; a fire-resistant layer covering the metal bar; and an insulating layer covering the fire-resistant layer and containing a resin, wherein the insulating layer has a resistance to a temperature of 260°C and 20 kgf / cm ２ An automotive bus bar having a melt flow rate under load of 50 g / 10 min or less.

3. An on-vehicle bus bar according to claim 1 or 2, wherein the insulator layer has a flash point of 370°C or higher as determined by the following method. (Method for checking flash point) (i) 3 g of the insulator layer is taken and placed in a combustion boat. (ii) The combustion boat is placed in a furnace with an air flow rate of 6.75 / min and a furnace pressure of 0.5 kgf / cm. ２ (iii) Visually check the state of the combustion boat introduced into the vertical furnace from when the temperature reaches the test temperature until 13 minutes have passed, and confirm whether ignition occurs. (iv) Repeat steps (i) to (iii) by changing the furnace temperature, and determine the lowest temperature at which ignition occurs within 13 minutes as the flash point.

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