Automotive Bus Bars

Abstract

An object of the present invention is to provide an in-vehicle busbar that maintains fire resistance and insulation performance even in the event of a long-term fire, etc. The in-vehicle busbar (10) that solves this problem includes 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). The insulator layer (40) contains a dynamically crosslinked product of a polyolefin resin and a rubber component, and the gel fraction of the insulator layer (40) measured in accordance with JIS C 3005:2014 4.25 is 70% or more.

Description

[Technical field]

[0001] The present invention relates to a busbar suitable for in-vehicle use. [Background technology]

[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 electric vehicles, not only the motor but also the brakes, steering wheels, doors, and windows are electrified. For this reason, when it is necessary 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 the power supply for a certain period of time and keep the electrical equipment running in order to secure time to evacuate and to inform others. Lithium-ion batteries, which are widely used as batteries, may deform and ignite due to external heating or self-heating. For this reason, lithium-ion batteries are protected as a unit in a robust, fire-resistant container. In addition, the bus bars need to be efficiently arranged in the limited space around the battery, and they also need to be fire-resistant.

[0003] Patent Document 1 describes a busbar wire having a flat conductor and an insulating coating that covers the flat conductor. The insulating coating is made of a heat-shrinkable polyolefin, polyvinyl chloride, fluorine-based resin, etc. The busbar wire is formed by placing the flat conductor inside the insulating coating and thermally shrinking the insulating coating with a heat gun, iron, etc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-6856 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the busbar electric wire of Patent Document 1, if a fire caused by an accident or poor maintenance occurs for a long time, the insulating coating may melt due to heat. If the molten coating falls from the busbar electric wire, there is a risk of secondary fire spread. Furthermore, if the insulating layer burns and is carbonized, the insulating performance of the insulating layer may decrease, and the damage may become even greater.

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

[0007] In order to solve the above problems, according to one aspect of the present invention, there is provided the following vehicle-mounted bus bar. [1] A metal bar; a fireproof layer covering the metal bar; an insulating layer covering the fire-resistant layer; having the insulator layer contains a dynamically crosslinked product of a polyolefin resin and a rubber component, The gel fraction of the insulating layer measured in accordance with JIS C 3005:2014 4.25 is 70% or more. the law of nature , The dynamically crosslinked product is obtained by dynamically crosslinking 100 parts by mass of the polyolefin resin and 20 parts by mass or more and 37.5 parts by mass or less of the rubber component in the presence of a crosslinking agent. Automotive bus bars. [2] The vehicle-mounted bus bar according to the above [1], The minimum insulation resistance value of the insulator layer while the in-vehicle bus bar is heated at 500° C. for 30 minutes is 1 MΩ or more. Automotive bus bars. [3] The vehicle bus bar according to the above [1] or [2], The gel fraction of the insulator layer is within a range of 72 to 75%. Automotive bus bars. [4] The vehicle-mounted bus bar according to any one of the above [1] to [3], The insulation layer further comprises a flame retardant. Automotive Bus Bars 。 Effect of the Invention

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

[0009] [Figure 1] FIG. 1A is a perspective view showing a configuration of an in-vehicle bus bar according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A. [Diagram 2] FIG. 2 is a flowchart of a method for manufacturing an in-vehicle bus bar according to an embodiment of the present invention. [Diagram 3] 3 is a graph showing the results of measurement of the insulation resistance value of an insulator layer at 500° C., measured in an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an in-vehicle busbar according to a preferred embodiment of the present invention will be described. In this specification, the symbol "to" indicating a numerical range means that the lower limit and upper limit are included in the numerical range.

[0011] (Configuration of automotive busbars) Fig. 1A is a perspective view showing a configuration of an in-vehicle busbar 10 according to one embodiment of the present invention, and Fig. 1B is a cross-sectional view taken along line AA in Fig. 1A. As shown in Fig. 1A and Fig. 1B, the in-vehicle busbar 10 of this embodiment has a metal bar 20, a fire-resistant layer 30 that covers the metal bar 20, and an insulating layer 40 that covers the fire-resistant layer 30. The insulating layer 40 of the conventional vehicle-mounted busbar 10 having the above-mentioned configuration has been made of polyolefin, polyvinyl chloride, fluorine-based resin, and silicone, which have heat shrinkability. However, the insulating layer 40 made of these resins is likely to melt and become more fluid when a fire or the like occurs and the temperature rises. The molten resin may fall to the surrounding area, causing a secondary fire spread. On the other hand, if the molten resin penetrates into the gaps in the fire-resistant layer 30, it may burn or carbonize. As a result, even if the insulating layer 40 or the fire-resistant layer 30 is provided, the insulating performance may decrease, and there is a concern that the damage may be further aggravated.

[0012] In contrast, the insulator layer 40 of the present embodiment contains a dynamically crosslinked product of a polyolefin resin and a rubber component. The insulator layer 40 has a gel fraction of 70% or more, as measured by a method described below. Even if the insulator layer 40 becomes hot and melts, the fluidity of the molten material is low. Therefore, even if a fire or the like occurs, the insulator layer 40 is not only unlikely to fall off the vehicle-mounted bus bar 10, but also unlikely to penetrate into the fire-resistant layer 30. As a result, the vehicle-mounted bus bar can maintain its fire resistance and insulation performance even if a fire occurs for a long period of time. Each component of the vehicle bus bar will be described below.

[0013] The metal bar 20 included in the vehicle-mounted bus bar 10 of this embodiment is a plate-shaped member formed of a conductive metal material. The material of the metal bar 20 is not particularly limited as long as it is conductive. Examples of the material of the metal bar 20 include copper or a copper alloy. The metal bar 20 may be composed of a single metal plate or a plurality of laminated thin metal plates. The thickness and width of the metal bar 20 are appropriately determined according to the magnitude of the current, the installation location, the installation conditions, and the like. When the metal bar 20 is a laminate of a plurality of thin metal plates, the thickness of the thin metal plate is within a range of 0.1 to 0.3 mm. In addition, the metal bar 20 formed by laminating a plurality of thin metal plates may have both ends welded together to have a structure that can 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.

[0014] The fire-resistant layer 30 is a layer disposed so as to cover the area of ​​the metal bar 20 other than the connection portion with the terminal. The fire-resistant layer 30 is, for example, made of an insulating fire-resistant tape wound transversely so as to cover the metal bar 20. The insulating fire-resistant tape only needs to have insulating properties, and may be made of one layer or two layers. Examples of insulating fire-resistant tape include mica tape and silicone tape. The mica (also called "mica") contained in the mica tape is a natural mineral and is a material with excellent electrical insulation and heat resistance. The mica tape may be a glass mica tape in which mica is bonded to a glass cloth. The mica tape may also 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 may be a tape composed of a laminate of a layer of silicone and a layer of glass cloth made of flat-woven glass fiber. When the insulating fireproof 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.

[0015] The insulating layer 40 is a layer disposed so as to cover the fire-resistant layer 30. As described above, the insulating layer 40 contains at least a dynamically crosslinked product of a polyolefin resin and a rubber component. The gel fraction of the insulating layer 40 is 70% or more. Here, the dynamically crosslinked product of the polyolefin resin and the rubber component refers to a product in which the polyolefin resin and the rubber component are crosslinked by applying a shear force in the presence of a crosslinking agent. The dynamically crosslinking can be carried out when the insulating layer 40 is prepared as a compound or when the insulating layer 40 is formed by extrusion molding or the like.

[0016] The polyolefin resin used as the material of the dynamic crosslinked product may be a resin mainly containing an olefin-derived structure. Specifically, the polyolefin resin may contain 50% by mass or more of olefin-derived structural units, and preferably 80% by mass or more of olefin-derived structural units, based on the total amount of structural units constituting the polyolefin resin. Examples of polyolefin-based resins include homopolymers of olefins, copolymers of two or more kinds of olefins, and copolymers of olefins and monomers other than olefins. The olefin preferably has 2 or more and 20 or less carbon atoms, and specific examples of the olefin include ethylene, propylene, butylene, 1-pentene, 4-methyl-1-pentene, 1-hexene, and 1-octene. Examples of monomers other than olefins that are copolymerizable with olefins include vinyl acetate, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, etc. 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, poly4-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 preferable.

[0017] 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) and their hydrogenated products; 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-paraalkylstyrene copolymer; silicone rubbers such as methylvinylsilicone rubber and dimethylsilicone 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 rubber components, olefin-based elastomers and styrene-based elastomers are preferred, with styrene-based elastomers being more preferred.

[0018] 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 from the viewpoint 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-butyl peroxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, tert-butylcumyl peroxide, etc. These may be used alone or in combination of two or more.

[0019] When obtaining a dynamically crosslinked product, the amount of the rubber component is preferably 15 parts by mass or more and 40 parts by mass or less, more preferably 17.5 parts by mass or more and 37.5 parts by mass or less, and even more preferably 20.0 parts by mass or more and 37.5 parts by mass or less, relative to 100 parts by mass of the polyolefin resin. By adjusting the mass ratio of the polyolefin resin to the rubber component within this range, it becomes easier to satisfy the above gel fraction. In this case, the amount of the crosslinking agent is preferably 0.1 to 0.5 parts by mass per 100 parts by mass of the polyolefin resin and the rubber component in total, in which case dynamic crosslinking can proceed efficiently and the gel fraction can be easily increased.

[0020] It is preferable that 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 the flame retardant 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. 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, based on the total amount of the dynamically crosslinked product and the flame retardant.

[0021] The insulator layer 40 may further contain a copper inhibitor. When the metal bar 20 is made of copper or a copper alloy, the 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 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 the copper inhibitor 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; and alcohol carboxylic acid esters. 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 damage prevention, 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, per 100 parts by mass of the total amount of the dynamically crosslinked material and the flame retardant.

[0022] In addition, in addition to the dynamically crosslinked material, flame retardant, and copper inhibitor described above, the insulator layer 40 may further contain known additives, fillers, and the like, as long as the purpose and effects of this embodiment are not impaired.

[0023] Here, the insulator layer 40 has a gel fraction of 70% or more as measured by the following method. The gel fraction is more preferably 72% or more and 75% or less. As described above, when the gel fraction is high, the insulator layer 40 is less likely to melt even at high temperatures, and even if it does melt, it is less likely to flow. Therefore, an in-vehicle busbar 10 with high fire resistance is obtained. The gel fraction is largely dependent on the degree of crosslinking of the dynamically crosslinked product, but is also affected by the amount of the flame retardant. The gel fraction of the insulator layer 40 is a value measured in accordance with JIS C 3005:2014 4.25 (degree of cross-linking). Specifically, as described in the above standard, only the insulator layer is separated from the vehicle bus bar and crushed to about 5 mm. 0.5 g of the sample is immersed in 50 g of xylene and heated to a temperature equal to or higher than the boiling point of xylene. The ratio of the mass of the sample after heating to the mass of the sample before heating, i.e., mass of the sample after heating / mass of the sample before heating×100, is defined as the gel fraction (%). The gel fraction in this specification is the average value of three measurements.

[0024] The minimum insulation resistance value of the insulator layer 40 during heating of the vehicle-mounted busbar 10 of this embodiment at 500°C for 30 minutes is preferably 1 MΩ or more, more preferably 10 MΩ or more, and even more preferably 40 MΩ or more. The higher the value, the better, so there is no particular upper limit. A high insulation resistance value means that when the insulator layer 40 is at 500°C, the molten material of the insulator layer 40 is unlikely to penetrate into the fire-resistant layer 30. The insulation resistance value of the insulator layer 40 can be measured, for example, by the following method. First, the vehicle-mounted busbar 10 is preheated to 500°C. Next, the insulator layer 40 is heated at 500°C for 30 minutes. During the 30 minutes of main heating, the insulation resistance value is measured multiple times with a mega tester. For example, the insulation resistance value is measured every 5 minutes from the start of main heating. The minimum insulation resistance value is then identified from the multiple measured values.

[0025] (Method of manufacturing in-vehicle busbars) Next, a method for manufacturing the above-mentioned vehicle-mounted busbar 10 will be described. Fig. 2 is a flowchart of the method for manufacturing the vehicle-mounted busbar 10. As shown in Fig. 2, the method for manufacturing the vehicle-mounted 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.

[0026] 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.

[0027] In the step (S120) of forming the fire-resistant layer 30 of this embodiment, the fire-resistant tape is wound laterally 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, a first piece of insulating fire-resistant tape is wound laterally with a certain gap. Then, a second piece of insulating fire-resistant tape may be further wound laterally with a predetermined overlap width on the first piece of insulating fire-resistant tape.

[0028] 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 of the dynamically cross-linked product (polyolefin resin, rubber component, and cross-linking agent), and, if necessary, a flame retardant, a copper damage inhibitor, etc., is prepared. Then, the resin composition is melt-extruded around the fire-resistant layer 30 to form the above-mentioned insulator layer 40. EXAMPLES

[0029] 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.

[0030] 1. Manufacturing of vehicle busbars (1) Example 1 A metal bar (width 20-30 mm × thickness 3-5 mm) made of rectangular copper was prepared. Two pieces of mica tape (MAT-1PM18W: manufactured by Okabe Mica Kogyosho) were wrapped horizontally around the metal bar with half of each tape overlapping to form a fire-resistant layer.

[0031] As shown in Table 1 below, 100 parts by mass of polypropylene, 27.5 parts by mass of a rubber component (styrene-based elastomer), and 0.3 parts by mass of a crosslinking agent (peroxide crosslinking agent), which are materials for the dynamic crosslinked product, were fed into a kneading extruder. Further, each component was further charged into the kneading extruder so that the amount of the dynamically crosslinked product and the flame retardant (magnesium hydroxide) was the composition shown in Table 2 below. Then, the resin composition (compound) was melted and kneaded, and extruded around the fireproof layer to form an insulating layer. The insulating layer had a thickness of 1 mm.

[0032] (2) Examples 2 to 5 and Comparative Examples 1 and 2 An on-vehicle bus bar was obtained in the same manner as in Example 1, except that the material of the dynamically crosslinked 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 crosslinking was not performed.

[0033] 2. Evaluation (1) Identification of gel fraction The gel fraction of the insulator layer of the vehicle-mounted busbars produced in the examples and comparative examples was measured in accordance with JIS C 3005:2014 4.25 (degree of cross-linking). Specifically, as described in the above standard, only the insulator layer was separated from the vehicle-mounted busbar and crushed to about 5 mm. 0.5 g of the sample was immersed in 50 g of xylene and heated to a temperature equal to or higher than the boiling point of xylene. The ratio of the mass after heating to the mass of the sample before heating, that is, the mass of the sample after heating / the mass of the sample before heating×100, was taken as the gel fraction (%). The average value of measurements taken three times by this method was taken as the gel fraction. The results are shown in Table 2.

[0034] (2) Measurement of minimum insulation resistance at 500°C The insulation resistance values ​​of the insulator layers of the vehicle-mounted busbars produced in the examples and comparative examples were measured by the following method. First, the vehicle-mounted busbars 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 busbars. Then, the vehicle-mounted busbars were preheated until the internal temperature reached 500°C. Then, the vehicle-mounted busbars were main-heated at 500°C for 30 minutes. During the main heating, specifically, the insulation resistance values ​​immediately after the start of the main heating, and 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, and 30 minutes after the start of the main heating were measured with a mega tester. Then, the minimum insulation resistance value during the main heating was identified. Additionally, the measurement results of the insulation resistance values ​​are shown in Figure 3. In Figure 3, the black circle symbols indicate the results of Example 1, the white circle symbols indicate the results of Example 2, and the black square symbols indicate the results of Example 3. Also, the white square symbols indicate the results of Comparative Example 2. The dotted line in Figure 3 indicates the heating temperature. The minimum insulation resistance value at 500°C was evaluated according to the following criteria. The results are shown in Table 2. 〇: Minimum insulation resistance at 500℃ is 1MΩ or more ×: Minimum insulation resistance at 500℃ is less than 1MΩ or burned

[0035] (3) Evaluation of sagging The presence or absence of sagging 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. The sagging was evaluated according to the following criteria. The results are shown in Table 2. ◯: The molten insulating layer did not fall. ×: The molten insulating layer fell.

[0036] (4) Measurement of brittle temperature Only the insulator layer was peeled off from the vehicle-mounted busbars produced in each of the Examples and Comparative Examples. Then, the brittle temperature of each layer was determined in accordance with JIS K7216 (1980). Evaluation was performed according to the following criteria. The results are shown in Table 2. ○: Brittle temperature is -50℃ or less ×: Brittle temperature is over -50℃

[0037] (5) Evaluation of heat resistance in vehicles The vehicle-mounted bus bars produced in each of the examples and comparative examples were subjected to an in-vehicle heat resistance test based on ISO19642-2 (2019). They were evaluated according to the following criteria. The results are shown in Table 2. ◎: 150℃ or higher ○: 125℃ or higher but less than 150℃ △: 105℃ or higher but lower than 125℃

[0038] 3.Results [Table 1]

[0039] [Table 2]

[0040] As shown in Table 2 above, in Examples 1 to 5 in which the insulator layer contains a dynamically crosslinked product of a polyolefin resin and a rubber component and has a gel fraction of 70% or more, all of them had high insulation resistance values ​​and good sagging evaluations. It is believed that in these insulator layers, even if the insulator layer becomes hot, the molten insulator layer does not easily enter the gaps in the fire-resistant tape layer, and the insulation resistance value does not easily decrease. It is also believed that sagging does not easily occur due to the low fluidity of the insulator layer under melting. Furthermore, the in-vehicle bus bars of Examples 1 to 3 and 5 also had good brittle temperatures and in-vehicle heat resistance.

[0041] On the other hand, when the gel fraction of the insulator layer was less than 70%, sagging occurred and the insulation resistance value decreased (Comparative Examples 1 and 2). One of the reasons for this is thought to be high fluidity of the molten insulator layer. [Industrial Applicability]

[0042] The vehicle-mounted bus bar of the present invention is useful, for example, as a bus bar for electrically connecting between an in-vehicle battery and an inverter, etc. [Explanation of symbols]

[0043] 10 Automotive Bus Bars 20 Metal Bar 30 Fireproof layer 40 Insulator Layer

Claims

1. A metal bar, A fire-resistant layer covering the aforementioned metal bar, An insulating layer covering the aforementioned fire-resistant layer, It is a vehicle-mounted bus bar having, The insulating layer comprises a dynamically crosslinked polyolefin resin and rubber components. The gel fraction of the insulating layer, measured in accordance with JIS C 3005:2014 4.25, is 70% or more. The aforementioned dynamically crosslinked product is obtained by dynamically crosslinking 100 parts by mass of the polyolefin resin and 20 to 37.5 parts by mass of the rubber component in the presence of a crosslinking agent. Bus bar for vehicles.

2. In the vehicle-mounted bus bar according to claim 1, The minimum insulation resistance of the insulating layer during heating of the vehicle-mounted busbar at 500°C for 30 minutes is 1 MΩ or more. Bus bar for vehicles.

3. In the vehicle-mounted bus bar according to claim 1, The gel fraction of the insulating layer is in the range of 72 to 75%. Bus bar for vehicles.

4. In the vehicle-mounted bus bar according to claim 1, The insulating layer further contains a flame retardant. Bus bar for vehicles.

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