Molded busbars and battery pack

Abstract

This suppresses the occurrence of resin cracks during heating or cooling of molded busbars. [Solution] The molded busbar 20 comprises a busbar 21 and a resin 22 containing fibers 221 that at least partially cover the busbar 21. The fibers 221 are irregularly oriented.

Description

Technical Field

[0001] The present invention relates to a molded bus bar and a battery pack.

Background Art

[0002] In recent years, various battery packs have been developed. A battery pack includes a battery module. A molded bus bar may be electrically connected to the battery module. The molded bus bar includes a bus bar and a resin that at least partially covers the bus bar.

[0003] Patent Document 1 describes a bus bar set. The bus bar set includes a plurality of bus bars and an insulating member that covers the plurality of bus bars and connects the plurality of bus bars. The bus bar set is formed by inserting the plurality of bus bars into a plurality of grooves of a first resin member, and injecting a second resin member onto the first resin member and the plurality of bus bars.

[0004] Patent Document 2 describes an electrode terminal. The electrode terminal includes a bent portion, a pair of flat portions formed at both ends of the bent portion, an electrode portion connected to one of the flat portions, and a conductive portion connected to the other of the flat portions. The thicknesses of the bent portion and the pair of flat portions are smaller than the thicknesses of the electrode portion and the conductive portion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of Invention

Problems to be Solved by the Invention

[0006] In molded busbars, the busbar and the resin covering it may expand when the temperature rises, and contract when the temperature falls. The busbar and the resin may have different coefficients of thermal expansion. Therefore, when the busbar and the resin expand or contract due to the temperature rise or fall of the molded busbar, it may become difficult to suppress the occurrence of cracks in the resin.

[0007] One example of the object of the present invention is to suppress the occurrence of resin cracks during heating or cooling of mold busbars. Other objects of the present invention will become apparent from the description herein. [Means for solving the problem]

[0008] One aspect of the present invention is as follows: 1. Bus bar and, The busbar is at least partially covered with a resin containing fibers, Equipped with, The aforementioned fibers are irregularly oriented, forming a molded bath bar. 2. The molded bath bar described in 1. wherein the fibers are distributed substantially uniformly. 3. The molded bath bar according to 1. or 2., wherein the fibers include at least one of glass fibers, carbon fibers, and aramid fibers. 4. A molded busbar as described in any one of 1. to 3., A battery module electrically connected to the molded busbar, A battery pack equipped with the following features. [Effects of the Invention]

[0009] According to the above embodiment of the present invention, it is possible to suppress the occurrence of cracks in the resin when the mold busbar is heated or cooled. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view of a portion of the battery pack according to the embodiment. [Figure 2]This is a plan view of the busbar according to the embodiment, with the resin removed. [Figure 3] This figure shows the first example of a cross-section along line AA in Figure 2. [Figure 4] This figure shows a second example of a cross-section along line AA in Figure 2. [Figure 5] This is a plan view of a modified busbar with the resin removed. [Figure 6] This is a diagram illustrating the resin of the molded busbar according to the embodiment. [Modes for carrying out the invention]

[0011] Embodiments and modified examples of the present invention will be described below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and their descriptions are omitted where appropriate.

[0012] Figure 1 is a perspective view of a portion of the battery pack 1 according to an embodiment.

[0013] Figure 1 illustrates the X, Y, and Z axes for illustrative purposes. The Z direction indicates the vertical direction of the battery pack 1. The X direction is one of the directions perpendicular to the Z direction. The Y direction is perpendicular to both the Z and X directions. Unless otherwise specified, the direction indicated by the arrow on the Z axis will be described as the vertical upward direction.

[0014] Unless otherwise specified, the +X side or +X refers to the side indicated by the arrow on the X axis, and the -X side or -X refers to the opposite side of the side indicated by the arrow on the X axis. Unless otherwise specified, the +Y side or +Y refers to the side indicated by the arrow on the Y axis, and the -Y side or -Y refers to the opposite side of the side indicated by the arrow on the Y axis. Unless otherwise specified, the +Z side or +Z refers to the side indicated by the arrow on the Z axis, and the -Z side or -Z refers to the opposite side of the side indicated by the arrow on the Z axis.

[0015] The battery pack 1 according to the embodiment includes a battery module 10, an electronic device 11, and a molded bus bar 20.

[0016] The battery module 10 includes a plurality of battery cells electrically connected in series, in parallel, or in a combination of series and parallel, and a casing that accommodates the plurality of battery cells. The battery module 10 shown in FIG. 1 illustrates the outer shell of the casing that accommodates the plurality of battery cells.

[0017] The electronic device 11 is located on the +X side with respect to the battery module 10. The electronic device 11 is, for example, a junction box. Instead of the electronic device 11, another battery module may be located on the +X side with respect to the battery module 10.

[0018] The molded bus bar 20 is electrically connected to the battery module 10 and the electronic device 11. Therefore, the battery module 10 and the electronic device 11 are electrically connected via the molded bus bar 20. The molded bus bar 20 includes a bus bar 21 and a resin 22.

[0019] The bus bar 21 is made of a metal such as copper or a copper alloy, for example. In the example shown in FIG. 1, when viewed from the +Z side, the bus bar 21 has a substantially L-shape including a portion extending in the X direction and a portion extending in the Y direction. When viewed from the -Y side, the -X side end of the portion of the bus bar 21 extending in the X direction is bent toward the +Z side relative to the remaining portion of the bus bar 21. A first fastening hole 21a is provided at one end on the -X side of the bus bar 21. The battery module 10 and the one end on the -X side of the bus bar 21 are fastened to each other by a fastener such as a bolt (not shown) passing through the first fastening hole 21a. A second fastening hole 21b is provided at the other end on the +X side of the bus bar 21. The electronic device 11 and the other end on the +X side of the bus bar 21 are fastened to each other by a bolt (not shown) passing through the second fastening hole 21b. The shape of the bus bar 21 is not limited to the example shown in FIG. 1.

[0020] The resin 22 covers the busbar 21 except for both ends. In a cross-section perpendicular to the extension direction of the busbar 21, the resin 22 surrounds the entire circumference of the busbar 21 except for both ends. The resin 22 contains resins such as polybutylene terephthalate (PBT), polypropylene (PP), polystyrene (PS), and polyphenylene sulfide (PPS), and fibers 221 such as glass fibers, carbon fibers, and aramid fibers, which will be explained later with reference to Figure 6. The resin 22 has electrical insulating properties. By covering the busbar 21 with the resin 22, contact and short circuits between the busbar 21 and surrounding conductive members can be suppressed.

[0021] Figure 2 is a plan view of the busbar 21 according to an embodiment with the resin 22 removed. Figure 3 is a diagram showing a first example of a cross-section along line AA in Figure 2. In Figure 2, the white circle with a black dot indicating the Z axis indicates that the Z-axis arrow is pointing towards the viewer on the page. In Figure 3, the white circle with a black dot indicating the X axis indicates that the X-axis arrow is pointing towards the viewer on the page.

[0022] As shown in Figures 2 and 3, multiple grooves 211 are formed on the +Z surface of the busbar 21, which is covered by the resin 22. The grooves 211 create an uneven surface on the +Z surface of the busbar 21 covered by the resin 22. In the example shown in Figure 2, three grooves 211 extend along the extension direction of the busbar 21 between the first fastening hole 21a and the second fastening hole 21b. In the example shown in Figure 3, the cross-section of each groove 211 perpendicular to the extension direction of the busbar 21 is approximately an inverted triangle. The number, planar shape, and cross-sectional shape of the grooves 211 are not limited to the examples shown in Figures 2 and 3. For example, the cross-sectional shape of the groove 211 may be a semicircle or a rectangle. The busbar 21 may have only one groove 211. The grooves 211 may be formed on the -Z surface of the busbar 21 instead of, or in addition to, the +Z surface of the busbar 21.

[0023] The busbar 21 and resin 22 may expand when the molded busbar 20 is heated, or contract when the molded busbar 20 is cooled. For example, the busbar 21 and resin 22 may expand due to the heat generated when the battery pack 1 is in use. Alternatively, the busbar 21 and resin 22 may contract when the molded busbar 20 is placed in an environment with a temperature lower than room temperature, such as ambient air. The busbar 21 and resin 22 may have different coefficients of thermal expansion. Therefore, if the busbar 21 and resin 22 expand or contract due to the heating or cooling of the molded busbar 20 while the +Z surface of the busbar 21 is flat and does not have grooves 211, the stress due to the difference in expansion or contraction between the busbar 21 and resin 22 may be excessively concentrated in the resin 22, making it difficult to suppress the occurrence of cracks in the resin 22. However, in this embodiment, the resin 22 fills into the groove 211, making it less likely for stress due to the difference in expansion or contraction between the busbar 21 and the resin 22 to concentrate in the resin 22. Therefore, compared to the case where stress due to the difference in expansion or contraction between the busbar 21 and the resin 22 is excessively concentrated in the resin 22, the occurrence of cracks in the resin 22 during heating or cooling of the molded busbar 20 can be suppressed.

[0024] From the viewpoint of making it easier for the resin 22 to enter the groove 211, it is preferable that the opening width W of the groove 211 is greater than or equal to any of the lower limits. The lower limit of the opening width W of the groove 211 is, for example, 1.5 mm. From the viewpoint of making it less likely for stress due to the difference in expansion or contraction between the busbar 21 and the resin 22 to concentrate in the resin 22, it is preferable that the opening width W of the groove 211 is less than or equal to any of the upper limits. The upper limit of the opening width W of the groove 211 is, for example, 4.0 mm. From the viewpoint of making it easier for the resin 22 to enter the groove 211, it is preferable that the depth D of the groove 211 is greater than or equal to any of the lower limits. The lower limit of the depth D of the groove 211 is, for example, 0.5 mm.

[0025] In the example shown in Figure 2, each groove 211 extends in the direction of extension of the busbar 21. Therefore, the resin 22 can be filled into the grooves 211 over substantially the entire region between the first fastening hole 21a and the second fastening hole 21b of the busbar 21. Consequently, compared to the case where grooves 211 are provided only in a portion of the region between the first fastening hole 21a and the second fastening hole 21b of the busbar 21, it is possible to suppress the occurrence of cracks in the resin 22 when the molded busbar 20 is heated or cooled.

[0026] Figure 4 shows a second example of a cross-section along line AA in Figure 2.

[0027] As shown in Figure 4, the cross-sectional shape of the groove 211 may be a substantially rectangular shape in which the width of the groove 211 in the Y direction is substantially constant regardless of its position in the Z direction. As shown in Figure 4, when the side surface of the groove 211 is substantially perpendicular to the +Z plane of the busbar 21, as shown in Figure 3, the resin 22 can be more easily caught in the groove 211 when a dimensional difference occurs between the busbar 21 and the resin 22 due to the difference in expansion or contraction of the busbar 21 and the resin 22. Therefore, in the example shown in Figure 4, when a dimensional difference occurs between the busbar 21 and the resin 22 due to the difference in expansion or contraction of the busbar 21 and the resin 22, the resin 22 can be less likely to come out of the groove 211, and the difference in expansion or contraction of the busbar 21 and the resin 22 can be more easily absorbed by the entire molded busbar 20.

[0028] From the viewpoint of making it easier for the resin 22 to enter the groove 211, it is preferable that the opening width W of the groove 211 is greater than or equal to any of the lower limits. The lower limit of the opening width W of the groove 211 is, for example, 1.5 mm. From the viewpoint of making it less likely for stress due to the difference in expansion or contraction between the busbar 21 and the resin 22 to concentrate in the resin 22, it is preferable that the opening width W of the groove 211 is less than or equal to any of the upper limits. The upper limit of the opening width W of the groove 211 is, for example, 4.0 mm. From the viewpoint of making it easier for the resin 22 to enter the groove 211, it is preferable that the depth D of the groove 211 is greater than or equal to any of the lower limits. The lower limit of the depth D of the groove 211 is, for example, 0.5 mm.

[0029] Figure 5 is a plan view of the busbar 21 in a modified state in which the resin 22 has been removed. The modified state shown in Figure 5 is the same as the embodiment except for the following points.

[0030] In the example shown in Figure 5, a plurality of recesses 212 are formed on the +Z surface of the busbar 21, which is covered by the resin 22. The plurality of recesses 212 create an uneven surface on the +Z surface of the busbar 21 covered by the resin 22. In the example shown in Figure 5, the plurality of recesses 212 are arranged in a grid pattern over substantially the entire region between the first fastening hole 21a and the second fastening hole 21b of the busbar 21. When viewed from the +Z side, each recess 212 is substantially circular in shape. The number and planar shape of the recesses 212 are not limited to the example shown in Figure 5.

[0031] In the example shown in Figure 5, the resin 22 fills into the recess 212, making it less likely for stress due to the difference in expansion or contraction between the busbar 21 and the resin 22 to concentrate in the resin 22. Therefore, compared to the case where stress due to the difference in expansion or contraction between the busbar 21 and the resin 22 is excessively concentrated in the resin 22, the occurrence of cracks in the resin 22 during heating or cooling of the molded busbar 20 can be suppressed.

[0032] From the viewpoint of making it easier for the resin 22 to enter the recess 212, it is preferable that the opening width of the recess 212 is greater than or equal to any of the lower limits. The lower limit of the opening width of the recess 212 is, for example, 1.5 mm. From the viewpoint of making it less likely for stress due to the difference in expansion or contraction between the busbar 21 and the resin 22 to concentrate in the resin 22, it is preferable that the opening width of the recess 212 is less than or equal to any of the upper limits. The upper limit of the opening width of the recess 212 is, for example, 4.0 mm. From the viewpoint of making it easier for the resin 22 to enter the recess 212, it is preferable that the depth of the recess 212 is greater than or equal to any of the lower limits. The lower limit of the depth of the recess 212 is, for example, 0.5 mm.

[0033] As can be seen from the explanation with reference to Figures 2 to 5, the occurrence of cracks in the resin 22 when the molded busbar 20 is heated or cooled can be suppressed by the irregularities formed on the surface of the busbar 21. These irregularities may be formed by grooves 211 shown in Figures 2 to 4, recesses 212 shown in Figure 5, or by a plurality of protrusions formed on the surface of the molded busbar 20. The plurality of protrusions may be, for example, a shape that is an inverted version of the groove 211 shown in Figure 3 or Figure 4, or ribs having a semicircular or rectangular shape. By forming a plurality of protrusions of appropriate height at appropriate intervals on the surface of the molded busbar 20, the resin 22 can be allowed to fill the gaps between adjacent protrusions. By allowing the resin 22 to fill the gaps between adjacent protrusions, the occurrence of cracks in the resin 22 when the molded busbar 20 is heated or cooled can be suppressed.

[0034] Figure 6 is a diagram illustrating the resin 22 of the molded busbar 20 according to the embodiment. In Figure 6, the multiple white arrows around the resin 22 indicate the injection positions of the resin 22 during the molding of the resin 22.

[0035] As shown in Figure 6, the resin 22 contains fibers 221. The fibers 221 include, for example, at least one of glass fibers, carbon fibers, and aramid fibers.

[0036] In the example shown in Figure 6, the fibers 221 are irregularly oriented. Because the fibers 221 are irregularly oriented, the orientation distribution of the fibers 221 is approximately uniform. If the fibers 221 were oriented in a specific direction, this could cause cracks in the resin 22 along the direction of fiber orientation when the molded busbar 20 is heated or cooled. For example, if the fibers 221 are oriented in the direction of elongation of the busbar 21, this could cause cracks in the resin 22 along the direction of elongation of the busbar 21. However, by oriented the fibers 221 irregularly, it is possible to reduce the likelihood of cracks forming in the busbar 21 along a specific direction. Therefore, compared to the case where the fibers 221 are oriented in a specific direction, the occurrence of cracks in the resin 22 during heating or cooling of the molded busbar 20 can be suppressed.

[0037] In the example shown in Figure 6, the fibers 221 are distributed almost uniformly throughout the resin 22. Therefore, compared to the case where the fibers 221 are unevenly distributed, it is easier to suppress the occurrence of cracks in the resin 22 during heating or cooling of the mold busbar 20 throughout the resin 22.

[0038] The orientation of the fibers 221 can be adjusted, for example, by the method of injecting the resin 22 during molding. For example, when molding the resin 22, if the resin 22 containing the fibers 221 is injected from the first fastening hole 21a to the second fastening hole 21b along the extension direction of the busbar 21, the flow of the resin 22 will orient the fibers 221 in the extension direction of the busbar 21. In contrast, as shown by the white arrows in Figure 6, if the resin 22 is injected from multiple locations on the side of the extension direction of the busbar 21, making it difficult for the flow of the resin 22 in a specific direction to form, the fibers 221 can be oriented irregularly.

[0039] The embodiments and modifications of the present invention have been described above with reference to the drawings, but these are merely examples of the present invention, and various other configurations can also be adopted. [Explanation of Symbols]

[0040] 1 Battery pack, 10 Battery module, 11 Electronic device, 20 Molded busbar, 21 Busbar, 211 Groove, 212 Recess, 21a First fastening hole, 21b Second fastening hole, 22 Resin, 221 Fiber

Claims

1. Bus bar and, The busbar is at least partially covered with a resin containing fibers, Equipped with, The aforementioned fibers are irregularly oriented, forming a molded bath bar.

2. The molded bath bar according to claim 1, wherein the fibers are distributed substantially uniformly.

3. The molded bath bar according to claim 1 or 2, wherein the fiber comprises at least one of glass fiber, carbon fiber, and aramid fiber.

4. A molded busbar according to claim 1 or 2, A battery module electrically connected to the molded busbar, A battery pack equipped with the following features.

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