Bus bar

Abstract

The present invention presents a bare bus bar structure design that prevents the occurrence of fire by ensuring the electrical stability of a bare bus bar and can be applied even in a confined space in an electric vehicle battery pack. According to the present invention, when an insulation sheath is extruded onto a bare bus bar, a uniform insulation thickness can be ensured, and taping can be performed without damaging a mica tape. In addition, provided is a bus bar structure, applicable to a battery pack for an electric vehicle and an energy storage system (ESS), that is structured such that the surface area of a conductor is increased so as to have improved heat dissipation characteristics, thereby having excellent electrical characteristics.

Description

bus bar

[0001] The present invention relates to a bus bar that secures electrical stability through the structural design of a bare bus bar to prevent fire and can be applied even in narrow spaces within an electric vehicle battery pack.

[0002]

[0003] Conventional busbar structures can be broadly divided into rectangular busbars and edge-round busbars with rounded corners. Rectangular busbars are designed as squares with right-angled corners. A particular problem with this structure is the current bottleneck phenomenon that occurs at the rectangular corners. As current is concentrated at the corners, heat generation increases in these areas, potentially overheating the busbar and increasing the risk of fire.

[0004] Furthermore, the corners of rectangular busbars increase the risk of tape damage during the mica taping process. This is because the sharp corners can easily tear or compress the tape during taping, potentially reducing its insulation performance. Furthermore, when extruding the insulation coating, the insulation thickness is uneven at the corners, particularly at the corners. This uneven insulation can lead to insulation breakdown, ultimately increasing the risk of fire due to electrical leakage.

[0005] Moreover, busbars with sharp corners can cause problems during bending. Sharp corners cause excessive shrinkage and expansion at the bending point, making it difficult to remove the product from the jig after bending. This process also increases the risk of appearance defects. Furthermore, sharp corners are prone to defects, which can lead to reduced durability in these areas over time. These defects can worsen over time, significantly reducing the reliability and safety of the busbar.

[0006] Therefore, the conventional rectangular busbar structure may have limitations in fields requiring high reliability and high safety, such as electric vehicle battery packs, due to these various problems.

[0007]

[0008] The present invention was developed to address the aforementioned issues, and is designed to be rigid to enable automated busbar processing. Furthermore, the cross-section of the bare busbar is optimized into an octagonal shape, preventing heat generation at the corners when current is applied. Furthermore, the increased surface area enhances heat dissipation, thereby ensuring electrical stability.

[0009] The present invention aims to provide a busbar structure that enhances durability by eliminating sharp edges prone to defects. Furthermore, the present invention aims to provide a busbar structure that improves workability by reducing expansion and contraction deviations during automatic bending.

[0010]

[0011] According to one embodiment of the present invention, a bare bus bar has a rectangular shape in which a width (W) is longer than a thickness (T) in a cross-sectional shape perpendicular to the longitudinal direction, and four corners are formed diagonally to form an octagonal shape, and the width (W) is 2 to 10 times the thickness (T) (W = Tx(2 to 10)).

[0012] The above width (W) may be 5 to 50 mm, and the above thickness (T) may be 2 to 20 mm.

[0013] It is preferable that the material of the above bare busbar is copper or aluminum.

[0014] At each corner of the rectangular shape, a corner edge is formed by a diagonal line connecting a position greater than 0.1xT and less than 0.5xT in the thickness (T) direction and a position greater than 0.1xT and less than (1 / 3)xW in the width (W) direction.

[0015] At each corner of the rectangular shape, a corner edge is formed by a diagonal line connecting a position of 0.2xT to 0.4xT in the thickness (T) direction and a position of 0.2xT to 0.4xT in the width (W) direction, respectively.

[0016] At each corner of the rectangular shape, a corner edge is formed by a diagonal line connecting the 0.3xT position in the thickness (T) direction and the 0.3xT position in the width (W) direction, respectively.

[0017] An insulating layer formed with a uniform thickness on the outside of the above bare bus bar may additionally be included.

[0018] The above bare busbar can be used in an electric vehicle battery pack or a power line of a vehicle, or in a battery pack of an energy storage system.

[0019]

[0020] The bare busbar structure according to the present invention can effectively prevent heat generation at each corner when current is applied. Compared to busbars with rounded corners, the increased surface area (see Fig. 1) provides excellent heat dissipation and thus prevents fire. In addition, by designing each corner of the busbar cross-section from a conventional right angle to an obtuse angle (an angle greater than 90° and less than 180°), damage to the tape can be prevented during mica taping, and when extruding the insulation coating, the insulation thickness can be prevented from thinning at the corners, thereby preventing fire caused by leakage due to insulation breakdown.

[0021] The structure according to the present invention is developed to be rigid, enabling automated bending, and its octagonal shape facilitates easy attachment and detachment of the bending jig, thereby improving workability. Furthermore, when installed in narrow spaces within an electric vehicle battery pack, the corner angles of the bare busbar cross-section are designed to be gentle, minimizing interference with other components compared to conventional designs. Furthermore, the structure according to the present invention eliminates the right-angled corner ends of conventional busbar structures, thereby reducing the risk of cracking during long-term use, thereby enhancing durability and product reliability.

[0022]

[0023] Figure 1 illustrates an increase in the surface area of ​​an octagonal cross-section bus bar according to the present invention compared to a bus bar with round corners.

[0024] FIG. 2a illustrates a cross-sectional view perpendicular to the longitudinal direction of a bare busbar according to the prior art, and FIG. 2b illustrates a cross-sectional view perpendicular to the longitudinal direction of a bare busbar according to an embodiment of the present invention.

[0025] Figure 3a is a drawing for explaining that the corners have been removed diagonally, and Figure 3b shows the shape with the corners removed.

[0026] Figure 4 shows the change in thickness according to position when a bare busbar is insulated, extruded, and bent.

[0027] Figure 5 shows a schematic diagram of cross-sectional changes during bending.

[0028] Figure 6 illustrates a design of the present invention in which a defect occurs and the design of the present invention in which such a defect is removed.

[0029] Figure 7 is a drawing comparing the structure of an extruded busbar with an insulation layer applied to various types of bare busbars manufactured in Table 1.

[0030] Figure 8 shows a result drawing of the electrical characteristics of the bare busbar by structure.

[0031] Figure 9 is a drawing explaining conditions for stably fixing an octagonal bus bar according to the present invention when mounted.

[0032] Various embodiments are now described with reference to the drawings, wherein like reference numerals are used throughout the drawings to designate like elements. For purposes of explanation, various descriptions are provided herein to facilitate an understanding of the present invention. However, it will be apparent that these embodiments may be practiced without these specific descriptions. In other instances, well-known structures and devices are presented in block diagram form to facilitate the description of the embodiments.

[0033]

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention is susceptible to various modifications and variations, and thus specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. Throughout the description of each drawing, similar reference numerals have been used to designate similar components.

[0035] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, steps, operations, components, parts, or combinations thereof.

[0036] In this specification, a bare bus bar means a bus bar in which the metal conductor is exposed as is without being coated with an insulating material.

[0037] The present invention relates to a bare busbar structure applied to battery packs of electric vehicles and energy storage systems (ESS), and more particularly, to a bare busbar structure designed in an octagonal shape by removing each corner end of the busbar cross-section diagonally, unlike a conventional rectangular busbar or a structure with rounded corners. Through this, a structural design is proposed that eliminates internal conductor defects and secures electrical stability. In the specification of the present invention, the octagonal-shaped bare busbar may be manufactured in an octagonal shape using an octagonal mold, or may be manufactured in a rectangular shape and then the corner ends may be removed diagonally to form the corners in a diagonal shape, thereby forming an octagonal shape. Any process method for obtaining an octagonal shape is not relevant.

[0038] FIG. 2a illustrates a cross-sectional view perpendicular to the longitudinal direction of a bare busbar according to the prior art, and FIG. 2b illustrates a cross-sectional view perpendicular to the longitudinal direction of a bare busbar according to one embodiment of the present invention.

[0039] As illustrated in Fig. 2a, the conventional press-rigid bare busbar structure is manufactured by pressing a plate into a rectangular cross-section perpendicular to its length. This rectangular bare busbar can be manufactured through extrusion, rolling, or drawing processes in addition to the pressing method. However, when applying a rectangular bare busbar to an automatic bending process, problems arise as the thickness (T) of the contracted portion expands during bending. In particular, it becomes difficult to remove the bare busbar from the bending jig, and defects such as dents or scratches may occur on the exterior.

[0040] To address these issues, the protruding right-angled edge portions of each corner are removed in an oblique direction, creating a space equivalent to the removed area, facilitating removal from the bending jig and reducing appearance defects. To address these issues, a bare busbar having an octagonal cross-section perpendicular to the longitudinal direction, as shown in Fig. 2b, was designed according to one embodiment of the present invention.

[0041] These octagonal-shaped bare bus bars can be manufactured by diagonally cutting the ends of each corner in a rectangular mold. Furthermore, octagonal bus bars can be manufactured using a mold designed in an octagonal shape through rolling, drawing, or extrusion processes. Alternatively, they can be manufactured using a slitting process, which involves diagonally cutting the corners of a square bus bar manufactured using the above processes. This slitting process allows the slit surfaces of each corner to be designed in a desired shape. This allows for the optimization of structural stability and electrical properties by diagonally cutting the corners to form an octagonal cross-section.

[0042] In summary, as illustrated in FIG. 2b, a bare bus bar according to one embodiment of the present invention has a rectangular shape in which the width (W) is longer than the thickness (T) in a cross-sectional shape perpendicular to the longitudinal direction, and four corners are removed diagonally to form an octagonal shape.

[0043] The width (W) is 2 to 10 times the thickness (T). That is, the relationship W = Tx (2 to 10) is established. To improve the conformal extrusion productivity and the quality of bare busbars, the optimal width (W) value relative to the thickness (T) is set as W = Tx (2 to 10). If the width is less than 2 times the thickness, the busbar will be unstable when fixedly installed in the intended application area. On the other hand, if the width exceeds 10 times the thickness, the width becomes excessively large compared to the thickness, which increases the possibility of the width becoming uneven during the extrusion, drawing, and rolling processes for manufacturing the busbar. In addition, this makes the bobbin alignment winding difficult, which hinders the production speed and increases the occurrence of quality defects. Therefore, setting the width of the octagonal bare busbar to between 2 and 10 times the thickness can improve productivity and prevent the occurrence of quality defects.

[0044] Preferably, the width (W) is 5 to 50 mm, and the thickness (T) is 2 to 20 mm. The width (W) of the octagonal bare busbar for application to the battery pack of an electric vehicle and an energy storage system and the power line of a vehicle is preferably set to 5 to 50 mm. If the width is less than 5 mm, the heat dissipation effect required for the high-voltage system of an electric vehicle is not sufficient, and the electrical resistance increases due to the increase in temperature when current is applied, which increases the electrical loss. On the other hand, if the width exceeds 50 mm, the space inside the battery pack becomes narrow, which may cause difficulties in installing the busbar. The thickness (T) of the octagonal bare busbar for application to the battery pack of an electric vehicle and an energy storage system and the power line of a vehicle is preferably set to 2 to 20 mm. If the thickness is less than 2 mm, there is a high possibility that the busbar will be damaged when tightening the bolts for fixing it after installation, and the fastening force may be weakened, making the fixing unstable. On the other hand, if the thickness exceeds 20 mm, the heat dissipation effect required for the high-voltage system of an electric vehicle is insufficient, and the electrical resistance increases due to the increase in temperature when current is applied, increasing electrical loss.

[0045] The bare busbar may be made of copper or aluminum. The bare busbar used in the battery pack of an electric vehicle and energy storage system according to one embodiment of the present invention is preferably made of copper or aluminum to ensure electrical properties with a conductivity of 55% IACS or higher and automatic bending performance. Here, the copper is more preferably of 99.9% purity or higher, and the aluminum is more preferably of 99.0% purity or higher.

[0046] According to one embodiment of the present invention, an octagonal bare busbar is formed such that its cross-section along the longitudinal direction forms an octagonal shape under the following conditions in order to form an octagonal shape. Fig. 3a is a drawing for explaining cutting corners diagonally, and Fig. 3b illustrates a shape with the corners cut off.

[0047] At each corner of the rectangular shape, a corner edge is formed by a diagonal line connecting a position greater than 0.1xT and less than 0.5xT in the thickness (T) direction and a position greater than 0.1xT and less than (1 / 3)xW in the width (W) direction. The corner edge refers to the length portion of the diagonal line forming the corner as a diagonal line in Fig. 3b.

[0048] The reason why it must exceed 0.1xT is that in the case of a square-shaped bare busbar of a conventional structure, defects (cracks, micropores) are observed under a microscope, which causes a problem of possible deterioration in durability during long-term use. It was confirmed that many of these defects exist within the range of 0.05xT in the thickness (T) direction and width (W) direction from both ends of each corner, and therefore, in the present invention, each corner of the bare busbar, which has a possibility of having defects in a range exceeding 0.1xT, is diagonally removed so that no defects are observed. Fig. 6 illustrates a design design of the present invention in which a defect occurs and such a part is removed.

[0049] In this case, it is more preferable to form the corner edges through diagonal lines connecting the positions 0.2xT to 0.4xT in the thickness (T) direction and the positions 0.2xT to 0.4xT in the width (W) direction at each corner of the rectangular shape.

[0050] Most preferably, the corner edges are formed by diagonal lines connecting the 0.3xT position in the thickness (T) direction and the 0.3xT position in the width (W) direction from each corner of the rectangular shape.

[0051] For example, in an octagonal busbar having a thickness of 4 mm and a width of 15 mm, the optimal range within which each corner can be slit diagonally is within a square area having sides greater than 0.4 mm and less than 2 mm in the T direction and greater than 0.4 mm and less than 5 mm in the W direction from each corner end of the busbar cross-section. More preferably, it is within a square area having sides greater than 0.8 mm and less than 1.6 mm.

[0052] Meanwhile, an insulating layer formed with a uniform thickness on the exterior of the bare bus bar may be additionally included. The bus bar of the present invention can be used in an electric vehicle battery pack or a power line of a vehicle, and can also be used in a battery pack of an energy storage system.

[0053] Below, the contents of the present invention will be further explained with specific examples.

[0054] Figure 4 illustrates the change in thickness according to location when a bare busbar is insulated, extruded, and bent. As shown in Figure 4, when transverse bending is performed, the thickness expands at location ① and contracts at location ②. The greater the thickness expansion at location ①, the more difficult it is for the bare busbar or insulated extruded busbar to be removed from the bending jig, resulting in poor workability and poor appearance (nicks, scratches).

[0055] Fig. 5 is a schematic diagram showing the change in cross-section during bending. In Fig. 5, the upper drawing shows the contraction-expansion appearance during bending in the case of a square-shaped busbar, and it can be seen that the expansion is very large at position ① of Fig. 4. The middle drawing shows that the expansion is large at position ① of Fig. 4 even in the case of a conventional edge-round shaped busbar, and the lower drawing shows the contraction-expansion appearance of an octagonal-shaped busbar like the present invention, and it can be seen that the expansion is not large at position ① of Fig. 4.

[0056] Table 1 below compares the bending characteristics of bare busbars by structure. When bending 180 degrees, the inner side of the bend expands and the outer side contracts. In this case, the octagonal shape, with a thickness expansion rate and thickness contraction rate variation of less than 10%, exhibits excellent bending workability and surface quality. In the octagonal shape, the gaps created by diagonal removal at each corner fill the gaps where the inner side expands during bending across the entire cross-section, resulting in a low thickness expansion rate and stable bending. In the case of the edge-rounded shape, the gaps in the rounded area are relatively small, resulting in a higher thickness expansion rate than the octagonal shape. In the case of the square shape, since there are no gaps at the edges, the thickness expansion rate is the highest, resulting in the greatest deformation during bending.

[0057]

[0058]

[0059] Figure 7 is a drawing comparing the structure of extruded busbars with an insulation layer applied to various types of bare busbars manufactured in Table 1. Square and hexagonal extruded busbars can develop wrinkles during bending due to uneven insulation thickness, which can lead to insulation breakdown at vulnerable areas. This increases the risk of fire due to current leakage. In the case of octagonal extruded busbars, the insulation thickness is maintained uniformly, preventing fire due to insulation breakdown. This is because the design range for forming diagonal edges in the T direction at each corner is less than T×0.5. This maintains insulation uniformity even during bending. On the other hand, in the case of the hexagonal shape, the insulation thickness is likely to be thinner at locations where there is a protruding angle in the center of the opposite side. This increases the risk of fire due to insulation breakdown, and there is also the possibility of the insulation being torn during bending. In particular, in the hexagonal shape, the design range for the T direction at each corner is set to T×0.5, which can lead to uneven insulation thickness formation. In summary, octagonal shaped extruded busbars can improve safety by maintaining uniform insulation thickness, whereas square and hexagonal shaped extruded busbars may cause problems during bending due to uneven insulation thickness.

[0060] Next, the electrical characteristics of bare busbars were compared according to their structures. An octagonal busbar according to the present invention and a square busbar were fabricated as a comparative example. Specimens of the same length (uniformly fabricated at both ends) were fabricated, with a cross-sectional area of ​​60 square meters. The evaluation equipment used an allowable current tester, applying a current of 1,000 A for a 10-minute application time.

[0061] Fig. 8 shows a result drawing of the electrical characteristics of the bare busbar according to its structure. As can be seen in Fig. 8, in the case of the square busbar, since the corner part has a small cross-sectional area, the current must pass through a narrow space, which causes heat generation, which has the problem of high possibility of power loss and fire. In contrast, in the case of the octagonal busbar according to the present invention, the corner angle is designed to be an obtuse angle, which is a gentle angle, from a right angle, so as to gently alleviate the flow of current and evenly distribute it, thereby preventing the current bottleneck phenomenon, and thereby confirming the effect of reducing heat generation.

[0062] Next, we compared the withstand voltage evaluation and measured the electrical resistance after mica taping according to the structure of the bare busbar. The withstand voltage evaluation (2.6kV x 1min) was performed after taping the bare busbar with mica No. 1. The mica taping was performed using a mica taping machine, and the mica tape is composed of multiple layers, specifically, resin / glass cloth / uncalcined phlogopite mica paper / glass cloth. Table 2 below summarizes the measurement results. As shown in Table 2, when mica taping was applied on a conventional square-shaped bare busbar, the tape tore due to the pressure from the sharp corners, resulting in a withstand voltage failure. In addition, in the case of a hexagonal-shaped bare busbar, the tape tore during bending due to the sharp angle, resulting in a failure.

[0063]

[0064]

[0065] Table 3 below summarizes the results of bending workability and electrical characteristics for a conventional square-shaped busbar, an edge-rounded busbar, a hexagonal-shaped busbar, and an octagonal-shaped busbar of the present invention in order to secure bending workability and quality (electrical characteristics and defect removal). As shown in Table 3, it can be seen that the edge removal point is preferably greater than 0.1xT and less than 0.5xT in the thickness (T) direction.

[0066]

[0067]

[0068] The establishment of the design according to Table 3 above is explained as follows.

[0069] As a result of evaluating the square busbar corresponding to Comparative Example 1, the increase rate of thickness expansion at the bending portion was high, making it difficult to attach and detach it when caught in the bending jig, and as a result, surface marks and scratches occurred at the busbar portion caught in the bending jig, resulting in poor bending workability. In addition, in the withstand voltage evaluation, the mica tape was occasionally torn at the sharp right-angled corners, resulting in defects in the withstand voltage, and in the allowable current evaluation, there was a problem of heat generation due to a current bottleneck at the corners. In particular, it was found that defects existed at the corners, which are most affected by the pressure in the W and T directions during busbar manufacturing.

[0070] In the edge round type busbar structure corresponding to Comparative Example 2, in the edge round type structure with the corner R value of 0.1 times the thickness T, the thickness expansion increase rate was low due to the small R, so it was possible to detach it from the bending jig, but the surface was engraved and scratched during the detachment process due to insufficient tolerance, resulting in poor bending workability. In this case, the right-angled part of the corner was removed, so some internal defects were eliminated, and since the corner was round, no heat was generated during the allowable current evaluation, and in the withstand voltage evaluation, the mica tape was not torn, so it passed the withstand voltage.

[0071] In the case of the octagonal busbar according to Comparative Example 3, in the design where a length of Tx0.1 was diagonally removed from both ends of each corner in the W and T directions, surface scratches occurred during the bending jig removal process due to the small allowance, and some internal defects were removed. Therefore, an area larger than the length of Tx0.1 must be removed in the W and T directions to completely remove the defects.

[0072] In the design in which the length Tx (0.2 to 0.4) was diagonally removed from both ends of each corner in the W and T directions according to Examples 4 to 6, sufficient allowance was provided to ensure excellent bending workability, and no heat generation occurred during the allowable current evaluation due to the removal of sharp corners. In addition, since the sharp corners were not removed, the mica tape was not torn during the withstand voltage evaluation, and thus passed the withstand voltage evaluation. When these conditions are satisfied, defects that may exist at the corners of both ends can be completely removed, and the optimal condition is when the corner removal in the W and T directions is Tx0.3.

[0073] In the case of Tx0.5 in the T direction corresponding to Comparative Example 7, a sharp angle is formed at the center of the opposite sides of the thickness, resulting in a hexagonal structure, which occasionally causes the mica tape to tear during the withstand voltage evaluation. Therefore, the T direction corner removal must be less than Tx0.5, and in the W direction, the length (A) of the flat opposite sides of the busbar cross section must be greater than the width (C) of the part forming the diagonal lines at both ends so that the busbar can be stably installed.

[0074] Fig. 9 is a drawing illustrating conditions for stably fixing an octagonal busbar according to the present invention when installed. As shown in Fig. 9, the busbar is stably fixed when installed when the width of the opposite side (A) is wider than the width of the area forming the diagonal line (C). In other words, the W-direction corner removal (C) must be < (1 / 3) x W.

[0075] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. As a bare bus bar, In a cross-sectional shape perpendicular to the length direction, the width (W) is longer than the thickness (T), and the four corners are formed diagonally to form an octagon. The width (W) is 2 to 10 times the thickness (T) (W = Tx(2 ~ 10)), Bear busbar.

2. In paragraph 1, The above width (W) is 5 to 50 mm, and the above thickness (T) is 2 to 20 mm. Bear busbar.

3. In paragraph 1, The material of the above bare busbar is copper or aluminum. Bear busbar.

4. In paragraph 1, At each corner of the rectangular shape, a corner edge is formed by a diagonal line connecting a position greater than 0.1xT and less than 0.5xT in the thickness (T) direction and a position greater than 0.1xT and less than (1 / 3)xW in the width (W) direction, Bear busbar.

5. In paragraph 1, At each corner of the rectangular shape, corner edges are formed through diagonal lines connecting positions 0.2xT to 0.4xT in the thickness (T) direction and positions 0.2xT to 0.4xT in the width (W) direction, respectively. Bear busbar.

6. In paragraph 1, At each corner of the rectangular shape, a corner edge is formed by a diagonal line connecting the position 0.3xT in the thickness (T) direction and the position 0.3xT in the width (W) direction, respectively. Bear busbar.

7. In paragraph 1, In addition, an insulating layer formed with a uniform thickness on the outside of the above bare bus bar is included. Bear busbar.

8. In paragraph 1, The above bare busbar is used for electric vehicle battery packs or vehicle power lines. Bear busbar.

9. In paragraph 1, The above bare busbar is used in the battery pack of the energy storage system. Bear busbar.

Images