JP4074012B2 - Method for manufacturing prismatic battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a prismatic battery, and more particularly to a method for manufacturing a prismatic battery by improving a welding method in which a sealing plate is welded to an open end of a prismatic case containing a power generation element to hermetically seal the prismatic case. .
[0002]
[Prior art]
For example, a secondary battery used as a power source of a portable electronic device is required to have a high energy density, and at the same time, a shape with good space use efficiency is required for weight reduction and miniaturization. As a battery that satisfies these requirements, lithium ion secondary batteries using a rectangular aluminum case are in the spotlight.
[0003]
Since this lithium ion secondary battery is required to have a stable sealing property over a long period of time, the sealing plate is joined by laser welding to the opening end of a rectangular case formed into a bottomed rectangular tube shape. Seal the edges. This laser welding has a feature that it has less thermal influence on the electrolytic solution and the electrical insulation portion accommodated in the case than other welding methods and has excellent work efficiency.
[0004]
Conventional methods for manufacturing a prismatic battery by laser welding between the rectangular case and the sealing plate are disclosed in JP-A-8-315788, JP-A-8-315789, and JP-A-8-315790. Things are known. In the manufacturing methods disclosed in these, a sealing plate is fitted into the opening end of a rectangular case arranged with the opening end facing upward, a laser beam is irradiated from the vertical direction to a contact portion between the rectangular case and the sealing plate, and laser By scanning and welding the contact line with a beam, the open end of the rectangular case is hermetically sealed with a sealing plate.
[0005]
[Problems to be solved by the invention]
However, in order to weld the contact portion between the sealing plate and the square case with a laser beam irradiated from the vertical direction to a square case arranged with the open end facing upward, a straight line with four sides of the open end shape is used. It is necessary to move the laser beam or the square case along the welding line formed at each corner connecting the parts, and the control of scanning the contact line to be welded with the laser beam becomes complicated and the production efficiency is low was there. In addition, if the contact part is welded by a laser beam irradiated from the vertical direction, the penetration direction of the penetration by welding is the internal direction of the battery, and there is a risk of the metal melt entering the battery when the penetration amount increases. is there. There is a limit to the processing accuracy of the plate material processed as a square case and a sealing plate, and even if the amount of penetration during welding is set to an optimal amount that does not reach the inside of the battery, due to variations in the processing accuracy of the plate thickness, If the melting reaches up to the point and the metal melt is scattered inside the battery, it causes an internal short circuit. Laser welding is a welding method that does not easily cause thermal effects on electrolytes and electrical insulators, but because the heating direction is toward the inside of the battery, the processing accuracy of the rectangular case and sealing plate or the limit of welding accuracy is limited. It is difficult to eliminate thermal effects from
[0006]
The present invention was devised in view of the above-mentioned problems of the prior art, and the object of the present invention is to easily perform scanning control of a laser beam for performing laser welding and to thermally influence the inside of the battery. It is an object of the present invention to provide a method for manufacturing a rectangular battery that enables welding between a rectangular case and a sealing plate by uniform welding without any problem.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention accommodates a power generation element in a rectangular case having a bottomed rectangular tube shape formed into an opening shape in which four sides of a quadrangle are straight and each corner has a curve with a predetermined radius, By laser welding a sealing plate to the opening end of the rectangular case, in the method of manufacturing a rectangular battery that seals the opening end of the rectangular case with the sealing plate, the sealing plate is brought into contact with the opening end of the rectangular case, A laser beam is incident from a side direction of the rectangular case to a contact line where the rectangular case and the sealing plate abut, and the laser beam is linearly scanned in a direction parallel to a straight line of four sides. between the sealing plate and a manufacturing method of a prismatic battery of laser welding, the direction of the burr generated at the contact line position when the respective prismatic case and sealing plate processing, the battery internal direction in prismatic cases, sealing Characterized in that was set to rectangular casing direction in the plate.
[0008]
According to the present invention , the sealing plate is in contact with the opening end of the rectangular case, and the contact line where the opening end and the sealing plate are in contact is formed on the upper end side portion of the rectangular case. The sealing plate is welded to the open end of the rectangular case by irradiating the abutting line with a laser beam from the side of the rectangular case and scanning in parallel with the four straight lines. In this welding method, since the scanning direction by the laser beam is a straight scanning line, the control is easy. Further, according to the present invention, the direction of the burr generated at the contact line position at the time of processing each of the rectangular case and the sealing plate is processed so as to be in the battery internal direction in the rectangular case and in the rectangular case direction in the sealing plate. As a result, there are no protrusions due to burrs at the incident position of the laser beam, and conversely the flatness is not impaired by the depression, resulting in poor appearance of welding due to the occurrence of spatter that melts and scatters, There is no occurrence of poor welding due to the loss of flatness, and the sealing plate can be accurately welded to the square case.
[0009]
In the manufacturing method described above, the four laser beams provided corresponding to each of the four sides are scanned in a direction parallel to the straight line of each side, and the respective contact lines are welded all at once. As the welding process proceeds simultaneously, the working efficiency is good and the sealing plate is not displaced by the welding operation.
[0010]
Welding of the sealing plate is possible by simultaneously welding any opposed contact lines by scanning each contact line sequentially with two or a single laser beam in parallel with the four straight lines and welding. Welding can be performed efficiently without causing positional displacement due to operation. Further, if the sealing plate is securely fixed on the rectangular case, it can be sequentially welded by scanning with a laser beam parallel to an arbitrary side.
[0011]
In addition, when the scanning with the laser beam moves between the straight part and the corner part of each side, by controlling the laser output according to the curve radius of the corner part, It is possible to compensate for uneven welding strength due to the difference in the focal length of the laser beam from the curved portion by changing the laser output, and to prevent the welding strength at the corner portion from being lowered.
[0012]
In addition, when scanning with the laser beam moves between the straight part and the corner part of each side, the linear side is controlled by changing the pulse time interval of the laser beam according to the curve radius of the corner part. The non-uniformity of the welding strength due to the difference in the focal length of the laser beam between the curved portion of the laser beam and the corner portion makes the laser beam irradiation amount per unit time equal by changing the pulse time interval of the laser beam, It can prevent that the welding strength of a corner part falls.
[0013]
In addition, by tilting the irradiation angle of the laser beam at a predetermined angle with respect to the scanning line direction, the incident angle of the laser beam with respect to the corner portion does not become shallow, so that a decrease in the welding strength at the corner portion is reduced. In addition, it is possible to eliminate damage to the laser launcher due to the reflection of the irradiated laser beam returning to the laser launcher.
[0014]
In addition, a plurality of rectangular cases with sealing plates placed on the open ends are arranged in a row, and a laser beam is emitted from the direction intersecting the arrangement direction, and each straight line on the opposite side parallel to the arrangement direction is irradiated with this laser beam. The rectangular cases arranged by placing the sealing plates are scanned by a laser beam scanned in the arrangement direction by welding parallel contact lines between the rectangular cases and the sealing plates. Laser welding is performed sequentially. By moving the laser beam relative to the square cases arranged in a row, a plurality of welds are made at once, and the production efficiency in the mass production process can be improved.
[0016]
Further, by performing welding so that the relationship between the welding nugget diameter d by the laser beam and the radius R of the corner portion is 0.3 <(d / R), generation of cracks due to laser welding can be suppressed. .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
[0018]
FIG. 1 shows the external shape of a prismatic battery according to the present embodiment. The prismatic battery 1 is sealed by welding a sealing plate 2 to the open end of the prismatic case 1 containing a power generation element. Is manufactured. The rectangular case 1 is formed in a square bottomed cylindrical shape, and the planar shape of the open end thereof is, as shown in FIG. 2, long sides a and b and short sides c and d are straight lines, The corner e is formed in a curve with a predetermined radius.
[0019]
The sealing plate 2 is formed in an outer shape having the same size as the outer size of the open end of the rectangular case 1. The sealing plate 2 is placed on the opening end of the rectangular case 1 and the contact line connecting the straight lines of the sides a to d with the curve of the corner portion e is laser-welded. The end is sealed by the sealing plate 2. A welding method between the open end of the rectangular case 1 and the sealing plate 2 will be described below.
[0020]
In FIG. 3A, the rectangular case 1 is placed at a predetermined position with its opening end facing upward and the cylinder forming axis of each cylinder being in the vertical direction, and the sealing plate 2 is placed covering the opening end. The state is shown from above, and the laser beams 3a to 3d are moved in parallel with the straight lines of the long sides a, b and short sides c, d, respectively, as shown in FIG. The contact line 4 where 1 and the sealing plate 2 contact is laser-welded, and the open end of the rectangular case 1 is sealed with the sealing plate 2. Thus, since the scanning direction by each laser beam 3a-3d is a straight line along each side a-d, the movement control is easy and it can perform a precise welding operation.
[0021]
As shown in FIG. 3, the laser welding procedure is performed by scanning the four laser beams 3a, 3b, 3c, and 3d with straight lines parallel to the long sides a and b and the short sides c and d. Since the welding operation to the sides a, b, c, d including the same progresses at the same time, even if the placed sealing plate 2 is not temporarily fixed on the rectangular case 1, the sealing plate 2 is not displaced and is efficiently welded. Processing can be performed. In the mass production process, as shown in FIG. 4 (a), a plurality of rectangular cases 1 with the sealing plate 2 in contact are arranged, and the laser beams 3c and 3d are turned on while relatively moving in the arrangement direction. -The short side c and d including each corner e are welded simultaneously by turning off, and then the length including each corner e left by changing the arrangement direction as shown in FIG. Sides a and b are laser welded. At this time, the laser beams 3a and 3b may be simultaneously irradiated onto the long sides a and b, but the laser beam 3a is welded so that one of the long sides a or b is welded so that the heating by the laser welding is not concentrated. Changing the scanning direction or the scanning position of 3b can suppress the thermal influence on the battery. Moreover, if it temporarily fixes so that the state which mounted the sealing board 2 in the square case 1 may not be displaced, it can also be made to weld sequentially from one side including the arbitrary corner | angular parts e.
[0022]
When scanning with the laser beam 3 parallel to the sides a, b, c, and d as described above, the focal length of the laser beam 3 becomes far at each corner e formed in a curve, and the corner e The ability of laser welding will be reduced. That is, as shown in FIG. 5, when the laser beam 3a is viewed, the scanning start position is on the curve of the corner portion e, and the position where the long side a is scanned is a maximum distance difference β from the focal length of the laser beam 3a. Occurs. This state is the same at the scanning end position, and when viewed with the laser beam 3c shown in FIG. 5, a maximum distance difference β is generated in the focal length of the laser beam 3c from the position where the short side c is scanned. The decrease in the welding strength of the corner portion e due to the distance difference β is eliminated by the following welding method.
[0023]
First, in the first method, the laser output is changed in accordance with the distance difference between the sides a to d at the positions where the corners e are scanned by the laser beams 3a to 3d. That is, a decrease in welding ability at the corner e where the focal distance is long can be compensated by an increase in laser output, so that uniform welding is performed over the entire circumference of the contact line 4.
[0024]
In the second method, at the positions where the corners e are scanned by the laser beams 3a to 3d, the emission time intervals of the laser pulses are changed corresponding to the distance differences from the sides a to d. . That is, control is performed so that the laser pulse emission time interval is shortened as the distance difference increases. Due to the change in the laser pulse emission time interval, the distance difference is compensated by the irradiation amount of the laser beam 3 per unit time, so that uniform welding is performed over the entire circumference of the contact line 4.
[0025]
In the laser welding to the contact line 4 described above, as shown in FIG. 6, the irradiation angle in the horizontal direction of each of the laser beams 3a to 3d is changed from the direction orthogonal to the sides a, b, c, d to an angle θ. By tilting, the incident angle of the laser beams 3a to 3d with respect to the corner e becomes deep, so that the laser beams 3a to 3d are less reflected and welding can be performed without reducing the welding strength. Further, the reflected light of the laser beam 3 irradiated on the contact line 4 does not return to the laser beam launch port, and damage to the laser beam launch port due to the reflected light is prevented. Further, by inclining the irradiation angle of the laser beams 3a to 3d, even if the welding strength at the corner e is lowered as described above without being corrected by a method such as a change in laser output, the uniform welding strength is obtained. Can be obtained.
[0026]
The diameter of the nugget that is melted by irradiation with the laser beam 3 is such that when each corner e is welded, the radius of the corner e is R and the nugget diameter is d, and the relationship is 0.3 <( d / R), the occurrence of cracks due to laser welding can be suppressed by adjusting the spot diameter and output of the laser beam 3.
[0027]
Further, as shown in FIG. 7, the laser beam 3a to 3d with respect to the contact line 4 is irradiated with the irradiation angle from the horizontal direction upward at an angle α, so that the thermal influence by laser welding does not reach the inside of the battery. Can be. The direction of laser welding according to the present embodiment is such that the thermal effect of laser welding hardly reaches the inside of the battery because the welding is performed from the side with respect to the upper end of the rectangular case 1 containing the power generation element. Thus, this is effective when the penetration has reached the inside of the battery due to the material thickness error of the rectangular case 1.
[0028]
The square case 1 and the sealing plate 2 use a thin aluminum plate for weight reduction and thinning, and the processing accuracy is limited. In particular, the square case 1 is bottomed by drawing. Since it is formed in a cylindrical shape, the thickness of the material tends to vary.
[0029]
Therefore, even if the amount of penetration of the contact line 4 due to the irradiation of each of the laser beams 3a to 3d is set constant, the penetration may reach the inside of the battery due to slight variations in the material thickness. FIG. 8 illustrates a state of laser welding with respect to the contact line 4 in a cross-sectional state. As shown in FIG. 8A, when the laser beam 3 is incident on the contact line 4 from the horizontal direction, As described above, when the melting reaches the inside of the battery due to the variation in the thickness of the thin plate material, since the power generation element is accommodated inside the battery, the penetration reaches the inside of the battery. Then, the metal melt in which the rectangular case 1 and the sealing plate 2 are melted is scattered inside the battery, which causes a battery failure due to an internal short circuit. Therefore, as shown in FIG. 8 (b), when the irradiation direction of the laser beam 3 is changed from the horizontal direction to the upward direction so as to be incident on the contact line 4, the progress direction of the melting is directed to the sealing plate 2 side. Therefore, even when the penetration becomes deeper, as shown by the broken line, it does not reach the inside of the battery, and scattering of the metal melt into the battery due to variation in material thickness is prevented.
[0030]
The square case 1 and the sealing plate 2 inevitably generate burrs in the cutting process for manufacturing them. FIG. 9 schematically shows the burrs 1a generated in the square case 1 and the burrs 2a generated in the sealing plate 2 in an exaggerated manner. Since the burrs 1a and 2a are generated as protrusions in the cutting direction, FIG. ) As shown in (b), when the burr 1a of the square case 1 is directed outward in the contact line to be welded, spatter that is melted and scattered by the laser beam 3 irradiated with the burr 1a occurs. The appearance of welding is poor.
[0031]
Further, as shown in FIG. 9A, when the burr 1a of the square case 1 faces outward and the burr 2a of the sealing plate 2 is formed on the contact side with the square case 1, the protrusion of the burr 2a As a result, the sealing plate 2 does not adhere to the square case 1, and when laser welding is performed in this state, not only spatter is generated but also welding defects are generated due to the gap between the contact lines. Further, as shown in FIG. 9C, when the burr 1a of the square case 1 is inward and the burr 2a of the sealing plate 2 is upward, a recess is formed in the contact line 4 and the flatness is impaired. This causes poor welding.
[0032]
Accordingly, as shown in FIG. 9D, when the cutting direction is set so that the burr 1a of the rectangular case 1 is inward and the burr 2a of the sealing plate 2 is downward, the sealing plate 2 is placed on the rectangular case 1. As shown in the figure, the inward depression by the burr 1a of the square case 1 is covered by the downward burr 2 of the sealing plate 2 as shown in the figure, and there is no protrusion or depression at the welded portion, and the burr 1a, Occurrence of poor welding due to 2a is prevented.
[0033]
【The invention's effect】
As described above, according to the present invention, a laser beam is incident on the opening end of the rectangular case from the side of the rectangular case with respect to the contact line on which the sealing plate is placed, and a straight line parallel to the four sides of the straight line. By scanning regularly, the rectangular case and the sealing plate are laser-welded, and the open end of the rectangular case is sealed by the sealing plate. In this welding method, since welding is performed by a linear operation parallel to each side, the control is easy. Further, since the restricting direction of the burrs produced on the contact line, the open end of the prismatic case with constant welding strength is locked securely hermetic by sealing plate.
[Brief description of the drawings]
FIG. 1 is a perspective view of a prismatic battery according to an embodiment of the present invention.
FIG. 2 is a plan view of an open end of a rectangular case.
3A is a plan view showing the scanning direction of the laser beam with respect to the contact line, and FIG. 3B is a side view showing the incident direction of the laser beam with respect to the contact line.
FIGS. 4A and 4B show an example of a laser welding process in which welding of a plurality of rectangular batteries is simultaneously performed, wherein FIG. 4A is a plan view showing welding on the short side and FIG. 4B is welding on the long side.
FIG. 5 is an explanatory diagram for explaining generation of a focal length difference of a laser beam with respect to a corner portion.
FIG. 6 is a plan view showing a method for scanning by tilting the incident angle of the laser beam in the horizontal direction.
FIG. 7 is a side view showing a method for scanning by tilting the incident angle of the laser beam in the vertical direction.
FIG. 8 is an explanatory diagram for explaining the effect of tilting the incident direction in the vertical direction.
FIG. 9 is a schematic diagram showing, in cross section, states (a) to (c) where the burr direction of the rectangular case and the sealing plate is inappropriate and states (d) where the burr direction is appropriate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Square case 1a, 2a Burr 2 Sealing plate 3, 3a, 3b, 3c, 3d Laser beam 4 Contact line a, b, c, d Straight edge e Corner part

Claims (8)

A power generation element is accommodated in a rectangular case with a bottomed rectangular tube shape in which the four sides of the quadrangle are straight and each corner has a curve with a predetermined radius, and a sealing plate is lasered at the opening end of the rectangular case. In the method of manufacturing a rectangular battery that seals the open end of the rectangular case by a sealing plate by welding,
A sealing plate is brought into contact with the open end of the rectangular case, and a laser beam is incident from the lateral direction of the rectangular case to a contact line where the rectangular case and the sealing plate are in contact. A method of manufacturing a prismatic battery that linearly scans in a direction parallel to a straight line and performs laser welding between the prismatic case and the sealing plate ,
The direction of the burr generated at the contact line position at the time of processing each of the square case and the sealing plate is in the direction of the battery inside in the square case and the direction of the square case in the sealing plate. Production method.   2. The method of manufacturing a prismatic battery according to claim 1, wherein the four laser beams provided corresponding to each of the four sides are scanned in a direction parallel to the straight line of each side, and the respective contact lines are welded together. .   2. The method of manufacturing a prismatic battery according to claim 1, wherein each contact line is sequentially scanned and welded with two or a single laser beam in parallel with a straight line of four sides.   4. The prismatic battery according to claim 1, wherein the laser output is controlled so as to change the laser output in accordance with the curve radius of the corner when scanning by the laser beam moves between the straight portion and the corner of each side. Manufacturing method.   The scanning with the laser beam is controlled so as to change the pulse time interval of the laser beam in accordance with the curve radius of the corner when moving between the straight portion and the corner of each side. The manufacturing method of the square battery of description.   The manufacturing method of the square battery as described in any one of Claims 1-5 which inclined the irradiation angle of the laser beam to the predetermined angle with respect to the scanning line direction.   A plurality of rectangular cases with sealing plates placed on the open ends are arranged in a row, and a laser beam is irradiated from the direction intersecting the row direction, and each linear portion on the opposite side parallel to the row direction is irradiated with this laser beam. The manufacturing method of the square battery as described in any one of Claims 1-6 which scans in parallel and welds the contact line of each square case and each sealing board.   The prismatic battery according to any one of claims 1 to 7, wherein welding is performed so that a relationship between a welding nugget diameter d by the laser beam and a radius R of the corner portion is 0.3 <(d / R). Method.

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