Battery assembly manufacturing method

Abstract

To solve the problem in which: a non-linear distribution of cell terminals in a battery pack increases the frequency of poor welds between the cell terminals and busbars and remedial work required.SOLUTION: A straight line passing through the center of a cell terminal group distribution is specified, and a welding jig is positioned with reference to the straight line. The maximum value of the amount of positional deviation between a pressing position and a cell terminal whose position is restrained by the welding jig is halved, and the necessary frequency of correction work is reduced.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] Disclosed herein is an improved battery assembly and method of manufacture. [Background technology]

[0002] Patent Documents 1 and 2 disclose battery packs in which a plurality of battery cells (hereinafter referred to as cells) are connected by bus bars. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-87704 A [Patent Document 2] International Publication No. WO2012 / 133711A1 Summary of the Invention [Problem to be solved by the invention]

[0004] In the assembly process of a battery pack, correction work is frequently required. This specification discloses a technique for reducing the frequency of the correction work required and improving the productivity of the battery pack. [Means for solving the problem]

[0005] The technology of the present specification improves the process of pressing and welding a bus bar to a cell terminal. In this process, the cell terminals are not necessarily distributed along a straight line, but may be distributed in a non-linear manner, for example, along a curved line. It has been found that correction work is required due to the non-linear distribution of the cell terminals. Therefore, the technology of the present specification measures the distribution of the cell terminals and determines the pressing position of the bus bar based on the measurement result. With this technology, even if the cell terminals are distributed in a non-linear manner, it is possible to prevent the pressing position of the bus bar from being significantly separated from the position of the cell terminal, reducing the frequency of the correction work required.

[0006] Details and further improvements of the technology disclosed in this specification are described in the following "Forms for Carrying Out the Invention". [Brief description of the drawings]

[0007] [Figure 1] The manufacturing process of the battery pack will be described. [Diagram 2] Explain why challenges arise. [Diagram 3] Explain why an improved manufacturing process would solve the problem. [Figure 4] The relationship between the busbar and the pressing position is shown. [Diagram 5] This shows the first step in identifying the line that passes through the center of the distribution. [Figure 6] The second step is to identify the line that passes through the center of the distribution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (Battery assembly process) Fig. 1(A) shows a top view of a cell 2. The cell 2 is a roughly flattened rectangular parallelepiped, with a positive electrode terminal 3 and a negative electrode terminal 4 exposed on the top surface. The positive electrode terminal 3 and the negative electrode terminal 4 are collectively referred to as cell terminals 5. Descriptions regarding the cell terminal 5 are common to both the positive electrode terminal 3 and the negative electrode terminal 4. The cell terminal 5 is insulated from the member forming the outer surface of the cell 2.

[0009] FIG. 1(B) shows a state where a plurality of cells 2 are stacked. The flat surfaces of adjacent cells 2 are stacked in a position facing each other. When the cell group is connected in series, the positive terminal 3 and the negative terminal 4 of the adjacent cell 2 are adjacent to each other, and the negative terminal 4 and the positive terminal 3 of the adjacent cell 2 are adjacent to each other. Here, the stacking direction is called the x direction, the longitudinal direction of the upper surface of the cell is called the y direction, and the height direction of the cell is called the z direction. In the figure, the cell group arranged in the middle range is not shown. There is no particular limit to the number of cells to be stacked, but the number of stacked layers n is, for example, 28 to 34. The suffix indicates the position in the x direction, that is, the stacking order of the cells 2.

[0010] Figure 1(C) shows the stacked cells compressed by applying pressure in the stacking direction. The arrow 8 extending in the x direction indicates the applied pressure. The compressed stacked cells are called a stack. In the following, the cell terminal on the positive side in the y direction is given the reference number 6, and the cell terminal on the negative side in the y direction is given the reference number 7.

[0011] FIG. 1(D) shows a state where a busbar 10 is arranged on the top surface of the stack. In the figure, suffixes are added according to the position in the x direction. Busbars 10-1, 10-3, ... are arranged on the negative side of the y direction, and busbars 10-2, 10-4, ... are arranged on the positive side of the y direction. Busbars 10-1, 10-2, ... are all the same, and common phenomena will be explained without suffixes. Busbar 10 spans adjacent positive electrode terminal 3 and negative electrode terminal 4.

[0012] Fig. 1(E) shows an enlarged view of the top surface of one busbar 10. A welding jig (not shown) is used to press the top surface of the busbar 10 from above in the z direction against the cell terminal 5, and in this state, the busbar 10 and the cell terminal 5 are welded together. The pressing positions are indicated by reference numbers 12 and 13, and the welding position is indicated by reference number 16. The busbar 10 is welded to each of the adjacent positive electrode terminal 3 and negative electrode terminal 4, and provides electrical continuity between the adjacent positive electrode terminal 3 and negative electrode terminal 4. Fig. 1(E) shows an example in which both sides of the welding position 16 are pressed in the y direction.

[0013] 1(D), busbars 10 include busbars 10-1, 10-3,... arranged on the negative side in the y direction, and busbars 10-2, 10-4,... arranged on the positive side in the y direction. In the following, as shown in Fig. 4, the pressing positions of busbars 10-2, 10-4,... arranged on the positive side in the y direction are denoted as 12 and 13, and the pressing positions of busbars 10-1, 10-3,... arranged on the negative side in the y direction are denoted as 14 and 15. The suffixes indicate the stacking order of cells 2.

[0014] The member that presses the upper surface of busbar 10 against cell terminal 5 is positioned by a welding jig (not shown), and presses four locations for each busbar, as shown in Fig. 4. For example, busbar 10-1 on the negative side in the y direction is pressed at positions 14-1 and 14-2 on the positive side in the y direction and positions 15-1 and 15-2 on the negative side in the y direction. Busbar 10-2 on the positive side in the y direction is pressed at positions 12-2 and 12-3 on the positive side in the y direction and positions 13-2 and 13-3 on the negative side in the y direction. The suffixes indicate the stacking order.

[0015] Pressing positions 15-1, 15-2, 15-3, 15-4,... on the negative y-direction side of busbars 10-1, 10-3,... are positioned on line 28 by a welding jig, and pressing positions 14-1, 14-2, 14-3, 14-4,... on the positive y-direction side are positioned on line 26 by a welding jig. Pressing positions 13-2, 13-3, 13-4, 13-5,... on the negative y-direction side of busbars 10-2, 10-4,... are positioned on line 24 by a welding jig, and pressing positions 12-2, 12-3, 12-4, 12-5,... on the positive y-direction side are positioned on line 22 by a welding jig.

[0016] (assignment) It was found that the compression process of Fig. 1(C) displaces the position of the cell terminal 5 in the y direction as shown in Fig. 2(A), which increases the frequency of the need for correction work. In Fig. 2(A), 5C indicates the center position of the cell terminal 5, and the subscripts indicate the stacking order. Fig. 2(A) illustrates a case where the centers 5C are not distributed along a straight line but along a curved line.

[0017] In the conventional technology, a straight line 18 passing through the center 5C-1 of the leftmost cell terminal 5 and the center 5C-n of the rightmost cell terminal 5 is calculated, and the position of the welding jig is determined based on the straight line 18. That is, the positions of the straight lines 22, 24, 26, and 28 in FIG. 4 are determined based on the position of the straight line 18. As a result, in the leftmost cell 2-1, as shown in FIG. 2(B), the formation range of the cell terminal 5 and the pressing positions 12 and 13 have the planned positional relationship, and the cell terminal 5 and the busbar 10 can be welded as planned. In contrast, FIG. 2(C) shows a case where the position of the cell terminal 5 is significantly displaced in the y direction. When the position of the cell terminal 5 is significantly displaced in the y direction, a phenomenon occurs in which the pressing positions 12 and 13 are displaced from the formation range of the cell terminal 5, and as a result, the cell terminal 5 and the busbar 10 cannot be welded as planned. In the case of Figure 2(A), in the middle range of the stacking direction (x direction), the positions of cell 2 and cell terminal 5 are significantly displaced in the y direction from their planned positions, and welding defects are likely to occur in this middle range, increasing the frequency of the need for correction work. Figure 2 shows the phenomenon that occurs in the busbar group on the positive side of the y direction, but the same phenomenon occurs in the busbar group on the negative side of the y direction.

[0018] (Solution) The distribution diagram in FIG. 3(A) is the same as the distribution diagram in FIG. 2(A), and shows a case in which the center positions 5C of the cell terminals 5 are not distributed in a straight line, but are distributed along a curved line. In the technology described in this specification, all of the center positions 5C of the individual cell terminals 5 are measured to identify their distribution, a straight line 20 passing through the center of the distribution is calculated, and the welding jig is positioned based on that straight line 20.

[0019] Figure 3(B) shows the relationship between the cell terminal 5 at the left end and the pressing positions 12, 13 when the position of the welding jig is determined based on the straight line 20. At the left end, the position of the cell terminal 5 is displaced toward the negative y-direction relative to the pressing positions 12, 13 from the planned position, indicating that pressing will be performed at a position of the cell terminal 5 that is biased toward the positive y-direction. In the case of Figure 3(B), even though the pressing positions 12, 13 are biased toward the positive y-direction of the cell terminal 5, this does not affect the phenomenon in which the upper surface of the busbar 10 is pressed against the cell terminal 5 at the pressing positions 12, 13, and does not result in poor welding.

[0020] Figure 3(C) shows the relationship between the cell terminal 5 near the center in the stacking direction and the pressing positions 12, 13 when the position of the welding jig is determined based on the straight line 20. Near the center, the position of the cell terminal 5 is displaced toward the positive y-direction relative to the pressing positions 12, 13 from the planned position, indicating that pressing is to be performed on a position of the cell terminal 5 that is biased toward the negative y-direction. In the case of Figure 3(C), even though the pressing positions 12, 13 are biased toward the negative y-direction side of the cell terminal 5, this does not affect the phenomenon in which the upper surface of the busbar 10 is pressed against the cell terminal 5 at the pressing positions 12, 13, and does not result in poor welding.

[0021] As described above, if all of the center positions 5C of the individual cell terminals 5 are measured to identify their distribution, a straight line 20 passing through the center of the distribution is calculated, and pressing positions 12, 13 are determined based on the straight line 20, the positional deviation in the Y direction between the cell terminals 5 and the pressing positions 12, 13 will take positive and negative values, and the absolute value of the positional deviation amount can be halved. This makes it possible to suppress the occurrence of welding defects and reduce the frequency of correction work. Although Figure 3 shows the phenomenon occurring in the busbar group on the positive side of the y direction, the same phenomenon occurs in the busbar group on the negative side of the y direction.

[0022] Here, the straight line passing through the center of the distribution may be a linear regression line or may be calculated using a simpler formula. For example, in Fig. 3(A), a straight line 20 is obtained that is parallel to a straight line 18 passing through the center 5C-1 of the leftmost cell terminal 5 and the center 5C-n of the rightmost cell terminal 5, and the straight line 20 is obtained such that the absolute value of the maximum deviation amount Y+MAX on the positive y-direction side from the straight line 20 is equal to the absolute value of the maximum deviation amount Y-MAX on the negative y-direction side, and this straight line is determined as the straight line passing through the center of the distribution. It is also possible to obtain a straight line 20 where the average value of the absolute value of the deviation amount on the positive y-direction side is equal to the average value of the absolute value of the deviation amount on the negative y-direction side. It is sufficient that the straight line has cell terminal centers 5C distributed on the left and right (both sides) of the straight line.

[0023] (2 straight lines) The above-mentioned straight line 20 can be calculated from the distribution of the cell terminals 6 on the positive side of the y direction in FIG. 1(C) or from the distribution of the cell terminals 7 on the negative side of the y direction. Even after the pressing step in FIG. 1(C), the distance between the cell terminals 6 on the positive side of the y direction of the cell 2 and the cell terminals 7 on the negative side of the y direction is almost the same, and the straight line 20 calculated from the distribution of the cell terminals 6 on the positive side of the y direction and the straight line 20 calculated from the distribution of the cell terminals 7 on the negative side of the y direction are almost parallel, and the distance between the two straight lines is equal to the distance between the cell terminals 6 on the positive side of the y direction of the cell 2 and the cell terminals 7 on the negative side of the y direction, which is known. As a result, when implementing this technology, the position of the welding jig may be adjusted based on the straight line calculated from the distribution of the cell terminals 6 on the positive side of the y direction, or the position of the welding jig may be adjusted based on the straight line calculated from the distribution of the cell terminals 7 on the negative side of the y direction. Alternatively, the position of the welding jig may be adjusted based on a straight line calculated from the distribution of cell terminals 6 on the positive side of the y direction and a straight line calculated from the distribution of cell terminals 7 on the negative side of the y direction, and the straight line calculated from the average value of these straight lines.

[0024] (Adjusting busbar position) As shown in FIG. 4, the pressing positions 12, 13, 14, and 15 are positioned on a straight line by a welding jig (not shown).

[0025] In contrast, the busbar 10 is positioned based on the positions of two adjacent cell terminals 5. That is, the busbar 10-1 on the negative y-direction side is positioned based on the positions of the cell terminals 7-1 and 7-2 on the negative y-direction side in FIG. 1(C), the busbar 10-2 on the positive y-direction side is positioned based on the positions of the cell terminals 6-2 and 6-3 on the positive y-direction side, the busbar 10-3 on the negative y-direction side is positioned based on the positions of the cell terminals 7-3 and 7-4 on the negative y-direction side, and the busbar 10-4 on the positive y-direction side is positioned based on the positions of the cell terminals 6-4 and 6-5 on the positive y-direction side. In this case, the relative positional relationship between the cell terminals 5 and the busbar 10 welded thereto is constant. The distribution of the center positions of the cell terminals 5 and the distribution of the center positions of the busbars 10 are equal. When the center positions of the cell terminals 5 are distributed along a curved line, the center positions of the busbars 10 are also distributed along the same curved line. In Figures 2(B) and 2(C) and Figures 3(B) and 3(C), the relative positional relationship between the cell terminals 5 and the bus bars 10 is assumed to be constant.

[0026] In response to this, it is possible to use a busbar arrangement jig to arrange the busbars 10-1, 10-3, ... on the negative side of the y direction on a straight line, and the busbars 10-2, 10-4, ... on the positive side of the y direction on a straight line, and then position the busbar arrangement jig with respect to the stack in Fig. 1(C). In this case, the straight line 20 shown in Fig. 3 is identified, and the busbar arrangement jig is positioned based on this straight line. As a result, when the cell terminals 5 are distributed along a curved line, the deviation in the y direction of the cell terminals 5 from the straight line on which the busbars are arranged is distributed between positive and negative, and the absolute value of the maximum deviation amount Y+MAX on the positive side of the y direction becomes equal to the absolute value of the maximum deviation amount Y-MAX on the negative side of the y direction, and the absolute value of the maximum deviation amount is halved.

[0027] In the above case, the welding jig can be positioned based on the busbar arrangement jig positioned as described above. When positioning the busbar arrangement jig, the present technology is used, and if the welding jig is positioned based on the busbar arrangement jig, the present technology is used for positioning the welding jig. EXAMPLES

[0028] The features of the embodiment will be described below. (insulating plate) In this embodiment, an insulating plate (not shown) is disposed between adjacent cells 2, 2 in FIG. 1B. A shape for positioning busbar 10 is formed on the upper surface of the insulating plate. As a result, busbar 10-1 on the negative y-direction side is positioned based on the positions of cell terminals 7-1, 7-2 on the negative y-direction side in FIG. 1C, busbar 10-2 on the positive y-direction side is positioned based on the positions of cell terminals 6-2, 6-3 on the positive y-direction side, busbar 10-3 on the negative y-direction side is positioned based on the positions of cell terminals 7-3, 7-4 on the negative y-direction side, and busbar 10-4 on the positive y-direction side is positioned based on the positions of cell terminals 6-4, 6-5 on the positive y-direction side.

[0029] (Stack housing) The stack shown in Fig. 1(C) is inserted into a case (not shown) and held in a compressed state. The top surface of the case is open, and the busbar arrangement process, the pressing process using a welding jig, and the welding process using a welding jig are performed from outside the case.

[0030] Depending on the structure of the stack housed in the case, a straight line passing from the center 5C-1 of the leftmost cell terminal 5 to the center 5C-n of the rightmost cell terminal 5 may extend along the longitudinal direction of the case. Figures 2(A) and 3(A) show this case, with the longitudinal direction of the case taken as the x-axis. On the other hand, there are cases where the line passing through the center 5C-1 of the leftmost cell terminal 5 and the center 5C-n of the rightmost cell terminal 5 is inclined with respect to the longitudinal direction of the case. In this case, if the longitudinal direction of the case is the x-axis, then the line 18 in Figure 2(A) is inclined with respect to the x-axis. In this case, the line 20 passing through the center of the distribution is also inclined with respect to the x-axis.

[0031] In Figure 5, the horizontal axis represents the x-direction position (corresponding to the stacking order of the cells) and the vertical axis represents the y-direction position of the center 5C of the cell terminal 5. The distribution of the center positions 5C of the cell terminals 5 is shown. A straight line 30 indicates a line that passes through the center 5C-1 of the leftmost cell terminal 5 and the center 5C-n of the rightmost cell terminal 5, and the inclination angle θ of this straight line 30 is found. This determines the relative rotation angle between the welding jig and the stack housing case that is required when aligning the jig with the stack housing case.

[0032] 6 is a graph showing the amount of deviation in the y direction from a straight line 30 on the vertical axis. The center positions 5C of the cell terminals 5 are distributed along a curved line. A straight line 32 is a straight line that reduces the absolute value of the maximum deviation Y+MAX in the positive y direction from the straight line 32 and the absolute value of the maximum deviation Y-MAX in the negative y direction by approximately half. The alignment of the welding jig with respect to the stack housing case is completed by translating the welding jig based on this straight line 32. By aligning the welding jig as described above, the absolute value of the maximum deviation in the Y direction between the pressing position and the cell terminal is halved, suppressing the occurrence of welding defects and reducing the frequency of the need for correction work.

[0033] In this embodiment, the welding position is determined based on the welding jig. In this embodiment, the welding point is pressed on both sides in the Y direction, but it may be pressed only on the positive side of the y direction of the welding position, or only on the negative side of the y direction. As described above, the welding position is determined based on the welding jig, so the distance between the pressing position and the welding position is managed. Depending on the distance, there are cases where it is necessary to press on both sides and cases where it is sufficient to press on one side. In this embodiment, a welding technique is used in which the back surface of the bus bar is welded to the cell terminal by processing from the top side of the bus bar. In this embodiment, a laser welding technique is used. The welding is not limited to laser welding. The welding here also includes brazing using a brazing material.

[0034] According to this technique, when the stack is viewed from above, a battery pack is obtained in which, although the cell terminals are distributed in a non-linear manner, the pressing marks caused by the pressing process extend along a straight line passing through the center of the distribution. Also, although the cell terminals are distributed in a non-linear manner, a battery pack is obtained in which the welding positions extend along a straight line passing through the center of the distribution.

[0035] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0036] 2: Battery cell 3: Positive terminal 4: Negative terminal 5: Cell terminal 6: Cell terminal on the positive side in the y direction 7: Cell terminal on the negative side in the y direction 8: Pressure 10: Busbar 12: Pressing position on the positive side of the bus bar in the y direction 13: Pressing position on the negative y-side busbar on the positive y-side 14: Pressing position on the positive side of the bus bar on the negative side of the y direction 15: Pressing position on the negative side of the bus bar in the y direction 16: Welding position 18,20,22,24,26,28,30,32: Straight line

Claims

[Claim 1] A method for manufacturing a battery pack, stacking a plurality of battery cells; applying pressure to the stacked battery cell group in a stacking direction; measuring the position of each cell terminal of the pressurized battery cell group; determining a straight line passing through the center of the distribution of the positions of the cell terminal group; a step of positioning a welding jig that determines a position at which the bus bar is pressed against the cell terminal based on the straight line; a step of welding the bus bar, which is biased toward the cell terminal by a welding jig, to the cell terminal; A manufacturing method comprising:

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