busbar

Abstract

A busbar according to the present invention has a conductor and an insulator layer covering the conductor. The busbar is characterized in that the insulator layer has a minimum thickness of 0.50 mm or more, and the insulator layer has a test force of 113 N or more when a 0.50 mm thick test piece produced using the constituent material is subjected to a tensile test according to JIS K 7127:1999 with the strain at 50%.

Description

Busbar

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

[0002] Conventionally, a battery unit and an inverter mounted on a battery electric vehicle, a hybrid vehicle, or the like are electrically connected by a bus bar. Generally, an on-board bus bar has a conductor and an insulating layer covering the conductor. The on-board bus bar is disposed in a limited space around the battery. Therefore, from the viewpoint of routing, the on-board bus bar is often bent in the thickness direction (flatwise bend) or the width direction (edgewise bend) (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-167282

[0004] As described in Patent Document 1, bus bars are bent. When the bus bar is bent, it is desirable that the insulating layer covering the conductor conform to the bending. If the insulating layer cannot conform to the bending sufficiently, cracks will occur in the insulating layer on the outside of the bent portion, and bulges will occur on the inside. These phenomena may adversely affect the insulation properties of the bus bar.

[0005] An object of the present invention is to provide a bus bar that does not cause bulging of the insulating layer when bent.

[0006] In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a busbar having a conductor and an insulating layer covering the conductor, wherein the insulating layer has a minimum thickness of 0.50 mm or more, and a tensile test is performed on a 0.50 mm thick test piece made from the insulating layer's constituent material in accordance with JIS K 7127:1999, and the test force at 50% strain is 113 N or more.

[0007] According to the present invention, a bus bar is provided in which the insulating layer does not bulge when bent.

[0008] Fig. 1A is a diagram showing a busbar according to an embodiment of the present invention, Fig. 1B is a cross-sectional view of the busbar according to the embodiment, Fig. 2 is a graph showing the relationship between the thickness of a test piece and the test force, and Fig. 3 is a diagram showing the conductor when the busbar is bent edgewise.

[0009] Hereinafter, busbars according to embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to the following embodiments. Busbars according to embodiments of the present invention are used, for example, to electrically connect an in-vehicle battery and an inverter. In this specification, the upper and lower limits of numerical ranges indicated by "to" are included in the numerical range.

[0010] [Busbar] FIG. 1A is a perspective view of a busbar 1, and FIG. 1B is a cross-sectional view of the busbar 1. As shown in FIG.

[0011] The bus bar 1 shown in Fig. 1A has a bent portion, and as shown in Fig. 1B, the bus bar 1 has a conductor 10 and an insulating layer 20 that covers the conductor 10.

[0012] The busbar 1 shown in Figure 1A has three bent portions: one edgewise bent portion 1a that is bent in the width direction of the busbar 1, and the remaining two flatwise bent portions 1b that are bent in the thickness direction of the busbar 1.

[0013] The conductor 10 and the insulating layer 20 of the bus bar 1 will be described below.

[0014] (Conductor) The conductor 10 is a plate-shaped member made of a conductive metal material. The material of the conductor 10 is not particularly limited as long as it is a metal. Examples of the material of the conductor 10 include copper or a copper alloy. In addition, in this embodiment, the conductor 10 is a thin plate having a curved portion. The conductor 10 may be made of a single metal plate or may be made of multiple stacked metal thin plates. The thickness and width of the conductor 10 are determined appropriately depending on the magnitude of the current, the installation location, the installation conditions, etc. When the conductor 10 is made of multiple stacked metal thin plates, the thickness of the metal thin plates is within the range of 0.1 to 0.3 mm. Furthermore, the conductor 10 made of multiple stacked metal thin plates may have both ends welded together.

[0015] The conductor 10 may have a structure at its end for connection to a terminal of, for example, a battery, etc. An example of such a structure includes a bolt receiving hole 11 for fastening with a bolt.

[0016] (Insulator Layer) The insulator layer 20 has an insulating function. Examples of materials for the insulator layer 20 include resin. The resin is preferably a thermoplastic resin. The thermoplastic resin is preferably flame-retardant. Examples of thermoplastic resins include polyamide, polyvinyl chloride, polyethylene, and polypropylene. In this embodiment, the insulator layer 20 directly covers the conductor 10 and is in contact with the conductor 10. Another layer may be disposed between the conductor 10 and the insulator layer 20. An example of a layer disposed between the conductor 10 and the insulator layer 20 is a fire-resistant layer. The fire-resistant layer is, for example, a layer formed of fire-resistant tape (e.g., mica tape). In addition, in this embodiment, no primer layer is present between the conductor 10 and the insulator layer 20.

[0017] The insulator layer 20 is configured to easily conform to the bending of the busbar 1. Specifically, in this embodiment, as shown in Fig. 3, when the conductor 10 is bent edgewise such that the radius of curvature on the inside of the conductor 10 is equal to the width R of the conductor 10, the insulator layer 20 is configured to have conformability such that cracks do not occur in the insulator layer 20 on the outside of the bend and bulges do not occur in the insulator layer 20 on the inside of the bend. In particular, the insulator layer 20 is configured so that bulges do not occur on the inside.

[0018] Here, since the insulator layer 20 has conformability, the minimum thickness of the insulator layer 20 is preferably 0.50 mm or more to prevent bulging, particularly on the inside. There is no particular upper limit to the minimum thickness of the insulator layer 20, but the minimum thickness of the insulator layer 20 is preferably 1.5 mm or less, for example. If the minimum thickness of the insulator layer 20 exceeds 1.5 mm, the terminal peelability will be poor.

[0019] Furthermore, since the insulator layer 20 has conformability, in order to prevent bulging, particularly on the inside, it is preferable that the insulator layer 20 resists deformation when an external force is applied to the insulator layer 20 due to bending, i.e., that the insulator layer 20 has a certain degree of strength. It is believed that if the insulator layer 20 has a certain degree of strength, the threshold at which the insulator layer 20 becomes unable to resist the external force and deforms in a direction that causes bulging (a phenomenon similar to buckling) becomes higher, thereby suppressing bulging. Specifically, a tensile test is performed on a 0.50 mm thick test piece made from the material constituting the insulator layer 20 in accordance with JIS K 7127:1999, and the material constituting the insulator layer 20 preferably has a strength such that a test force of 113 N or more is obtained at a strain of 50%. Details of these points will be described later with reference to examples.

[0020] The insulator layer 20 is preferably formed on the conductor 10 heated to about 160 to 200° C. Specifically, the insulator layer 20 is preferably formed by extrusion molding a resin onto the conductor 10 heated to about 160 to 200° C.

[0021] (Effects) In the busbar 1 according to this embodiment, the minimum thickness of the insulator layer 20 is 0.50 mm or more, and when a tensile test is performed on a 0.50 mm thick test piece made from the constituent material of the insulator layer in accordance with JIS K 7127:1999, the test force at 50% strain is 113 N or more. As a result, when the busbar 1 is bent edgewise, the insulator layer 20 conforms to the bend, suppressing cracking of the insulator layer 20 on the outer side of the bend and bulging of the insulator layer 20 on the inner side of the bend. This also suppresses adverse effects on the insulation performance of the busbar 1.

[0022] The present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0023] [Experiment 1] Experiment 1 was conducted to examine the strength of the material constituting the insulator layer of the bus bar.

[0024] In Experiment 1, test specimens were prepared in accordance with JIS K 7127:1999 using polyamide 12 as the material for the insulator layer, with thicknesses of 0.50 mm, 0.90 mm, and 1.3 mm. Five test specimens were prepared for each of the thicknesses of 0.50 mm, 0.90 mm, and 1.3 mm. Furthermore, tensile tests were performed on each of the prepared test specimens in accordance with JIS K 7127:1999 at a tensile speed of 100 mm / min, and the test force at a strain of 50% was measured. The actual thickness of each test specimen was also measured. The thickness of each test specimen was measured using an electronic thickness gauge at three random locations, and the average value was used as the thickness of the test specimen. The measured thicknesses and test forces of the test specimens are shown in Table 1. A graph plotting the relationship between the thickness of the test specimens in Table 1 and the test force is shown in Figure 2.

[0025]

[0026] As can be seen from Table 1 and the graph shown in Figure 2, the thickness of the test piece and the test force are proportional to each other, and each plot is located on a straight line, which can be approximated by a linear function.

[0027] [Experiment 2] Experiment 2 was conducted to examine the relationship between the minimum thickness of the insulator layer of the bus bar and bending workability (occurrence of cracks and blistering).

[0028] In Experiment 2, busbars were fabricated using flat copper wire (20 mm wide x 3.5 mm thick) as the conductor. The flat copper wire was heated to 160°C to 200°C, and polyamide 12 was used as the thermoplastic resin. The extrusion molding conditions were varied to achieve various insulation layer thicknesses. The minimum insulation layer thicknesses of the fabricated busbars were measured, and the results are shown in Table 2. The minimum insulation layer thicknesses of the fabricated busbars were measured on the cross section of the busbar using a digital microscope (Keyence Corporation). Specifically, the insulation layer thickness covering a 20 mm width of the conductor was measured at six locations: the center of the conductor width and positions approximately 1.0 mm inward from the left and right edges of the conductor width. The insulation layer thickness covering a 3.5 mm thickness of the conductor was measured at two locations: the center of the conductor width on each side of the busbar. As a result, the coating thickness of the insulator layer was measured at a total of eight locations, and the smallest value among these was taken as the minimum thickness of the insulator layer, which is shown in Table 2.

[0029] Busbars having various minimum insulation layer thicknesses as described above were bent edgewise so that the inner radius of curvature of the conductor (rectangular copper wire) was 20 mm (the same length as the width of the conductor), as shown in Figure 3. The busbars were visually evaluated for the occurrence of cracks in the insulation layer on the outer side of the bend and for the occurrence of bulges in the insulation layer on the inner side of the bend. The evaluation results are shown in Table 2.

[0030]

[0031] As can be seen from Table 2, no cracks occurred when the minimum thickness of the insulator layer was within the range of 0.39 to 0.64 mm. On the other hand, bulging occurred when the minimum thickness of the insulator layer was within the range of 0.39 to 0.45 mm, but did not occur when the minimum thickness was 0.50 mm or greater. This shows that the minimum thickness of the insulator layer made of polyamide 12 is 0.50 mm or greater to ensure good conformability and prevent bulging when the bus bar is bent.

[0032] Furthermore, combining the results in Tables 1 and 2, it is believed that blistering can be suppressed if the strength and thickness of the insulator layer of the bus bar are as follows: That is, when a tensile test is performed on a test piece with a thickness of 0.50 mm in accordance with JIS K 7127:1999, it is believed that blistering can be suppressed if the insulator layer is formed to a minimum thickness of 0.50 mm or more using a resin (composition) that produces a test force of 113 N or more at 50% strain.

[0033] This is because, as described above, blistering is thought to occur due to insufficient strength of the insulator layer, and a test force of 113 N or more under the measurement conditions described above is thought to provide sufficient strength and suppress blistering. That is, when the insulator layer is made of a material with a strength of 113 N or more, the threshold at which the insulator layer becomes unable to resist the external force associated with edgewise bending and deforms in the direction causing blistering (a phenomenon similar to buckling) is increased, suppressing blistering. As can be seen from the results in Table 2, if the insulator layer has a thickness and strength sufficient to prevent blistering in the inner insulator layer when bent edgewise, cracks will not occur in the outer insulator layer.

[0034] The bus bar obtained by the present invention is useful as a bus bar that may be bent for routing purposes, such as a bus bar for electrically connecting an in-vehicle battery and an inverter.

[0035] REFERENCE SIGNS LIST 1 busbar 1a edgewise bent portion 1b flatwise bent portion 10 conductor 11 bolt receiving hole 20 insulator layer

Claims

1. A busbar having a conductor and an insulating layer covering the conductor, wherein the insulating layer has a minimum thickness of 0.50 mm or more, and wherein a tensile test is conducted in accordance with JIS K 7127:1999 on a 0.50 mm thick test piece made from the material of the insulating layer, and the test force at 50% strain is 113 N or more.

2. The busbar according to claim 1, wherein the conductor is copper or a copper alloy, and the insulating layer is polyamide resin.

3. A busbar according to claim 1 or 2, characterized in that there is no primer layer between the conductor and the insulating layer.

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