JPH08315788A - Manufacture of square battery - Google Patents

Abstract

PURPOSE: To provide a welding method of a sealed vessel of a square battery by which a square case can be thinned without incurring reduction in welding strength and the deterioration of the welding finish. CONSTITUTION: A cover plate 2 composed of a metallic plate is fitted in a square opening formed on one end of a metallic case 1, and a fitting 3 is welded in order by a laser, and a sealed vessel of a square battery is formed. The spot center of a laser beam is offset inside the fitting part 3. By doing in this way, since the outer peripheral end of a melting-into area becomes hard to reach the outer peripheral end of the square case 1 by this offset quantity, failure of a shape such as the outer peripheral end of the square case 1 hangs down outside and a recess is generated in a welding area is not caused, and reduction in welding strength thereby can also be prevented.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a prismatic battery.

[0002]

2. Description of the Related Art In a closed prismatic battery disclosed in Japanese Patent Publication No. 6-54660, a lid plate made of a metal plate is fitted into an opening formed at one end of a prismatic case made of metal, and is fitted to a fitting portion. Laser welded to form a prismatic battery container.
It should be noted that such prismatic batteries have better space utilization efficiency than cylindrical batteries, and laser welding has less thermal influence on the electrolytic solution and electrically insulating parts compared to other welding methods, resulting in higher work efficiency. Has the advantage of being excellent.

[0003]

In batteries, it is always desired to improve the volumetric efficiency and the weight efficiency. For this reason, the thinness of the rectangular case can reduce the weight of the battery case and increase the internal volume. It is very effective. However, in the conventional laser welding method (see FIG. 7) in which the spot center of the laser beam is aligned with the fitting portion to match the deepest point of the penetration area with the fitting portion, such a rectangular case is made thinner. Then, as shown in FIG. 8, there is a possibility that the outer peripheral edge of the melted region reaches the outer peripheral edge of the rectangular case and solidifies in a state where the outer peripheral edge of the rectangular case hangs outward. In addition, the outer dimensions of the rectangular case may be larger than the standard dimensions, and the welded area (melted-in area) may be hollowed to cause a problem of weakened welding strength. In addition, FIG.
In FIG. 8, 1 is a rectangular case, 2 is a cover plate, 3 is a fitting portion, and b is the above-mentioned hanging portion.

As a matter of course, it is conceivable that the spot diameter of the laser beam is narrowed as the thickness of the rectangular case is reduced, thereby narrowing the width of the melted region. But,
Such narrowing of the width of the melted region causes a decrease in the depth of the melted region, resulting in a decrease in welding strength. The present invention has been made in view of the above problems, and an object thereof is to provide a method for manufacturing a prismatic battery capable of reducing the thickness of a prismatic case without lowering the welding strength or deteriorating the welding finish. .

[0005]

According to a first aspect of the present invention, a rectangular battery is formed by fitting a lid plate made of a metal plate into a rectangular opening formed at one end of a metal case and sequentially laser-welding the fitting portions. To form a container. Further, in this method, the spot center of the laser beam is offset inside the fitting portion. This makes it difficult for the outer peripheral edge of the melted region to reach the outer peripheral edge of the rectangular case by this offset, so that the outer peripheral edge of the rectangular case hangs outward, or there is a defect in the shape such as a depression in the welding area. It does not occur, and it is possible to prevent a decrease in the welding strength.

According to the second aspect of the present invention, the lid plate is fitted into the opening of the metal case having a rectangular cross section having the battery element therein, and the fitting portion is joined by laser welding. Further, in the present method, a line that is offset inward by a predetermined dimension range over the entire circumference of a linear fitting portion consisting of a linear side portion and a curved corner portion that joins a pair of adjacent side portions. Laser welding is performed by aligning the spot center of the laser beam with the (scanning path). With this configuration, the same effect as that of the first aspect can be achieved.

The method according to claim 3 is the method according to claim 1 or 2.
In the described method, further, the X and Y tables are used, and the plane scanning control of the laser spot is performed by making the mounting surface parallel to the plane including the fitting portion to be welded, which simplifies the apparatus configuration. Can be planned. In the method according to claim 4, in the method according to any one of claims 1 to 3, the cover plate is fitted into the opening of the case by press fitting, so that the cover plate is displaced before welding or temporary fixing. Can be prevented.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below based on Examples. (Example) An example of a method for manufacturing a prismatic battery of the present invention will be described with reference to FIGS. The pulse type laser welding machine is shown in FIG. This welding machine is provided with an X and Y table 6 on which a battery assembly 100 to be welded is placed and fixed and is displaced in horizontal X and Y directions, respectively, and above the X and Y table 6. It is composed of a laser oscillator 7 for vertically irradiating a laser pulse, and a controller 8 which is composed of a personal computer and controls the X and Y tables 6 and the laser oscillator 7. Reference numeral 70 denotes an objective lens for focusing (focusing) the laser beam emitted from the laser oscillator 7. The laser oscillator 7 is fixed above the X and Y table 6.

FIG. 2 shows a prismatic battery to which the welding method of this embodiment is applied. The container of this battery comprises a rectangular case (metal case in the present invention) 1 and a lid plate 2 which is fitted into an opening at the upper end of the rectangular case 1 and is laser-welded to seal the opening. A positive electrode terminal (not shown) fixed to the central portion of the cover plate 2 by being electrically insulated from the cover plate 2
Is provided.

The rectangular case 1 has a rectangular box shape and is formed by molding a nickel-plated steel plate. In the rectangular case 1, a battery element 9, that is, a positive electrode active material made of lithium cobalt oxide, a separator, a negative electrode active material made of carbon, and a non-aqueous electrolyte solution are housed. The lid plate 2 is made of a nickel-plated steel plate (the periphery of which is not plated) with a very small clearance between the lid plate 2 and the entire circumference of the opening by being press-fitted into the opening.
After being fitted in the opening of the cover plate 2, the outer peripheral edge of the lid plate 2 is kept in contact with the inner periphery (opening edge) of the opening of the rectangular case 1, while the fitting portion 3 is output over the entire periphery of the output 310 described above.
The rectangular case 1 is made into a container by welding with the pulse type YAG laser welding machine of (W). Therefore, the fitting portion 3 is composed of the opening edge of the rectangular case 1 (the inner peripheral edge of the opening) and the outer peripheral edge of the lid plate 2.

The state of laser welding is shown in FIG. The corners of the opening of the rectangular case 1 and the corners of the cover plate 2 fitted therein are made to have a constant curvature, and therefore the corners 32 of the fitting part 3 are formed.
Is also curved with a constant curvature. Reference numeral 31 is a side portion that forms a straight line portion of the fitting portion 3. Hereinafter, the welding process will be further described with reference to FIG. First, the rectangular case 1 has a width of 16 mm, a length of 7.5 mm, a height of 83.5 mm, and a thickness of 0.3.
It is formed by forming a nickel-plated steel sheet of mm. The cover plate 2 is
Horizontal 15.4 mm, vertical 6.9 mm, thickness 0.6 mm
It is formed by forming a nickel-plated steel sheet. The laser pulse is emitted at an interval of 100 pulses / second, and the scanning speed of the laser beam along the fitting portion 3 is 500 mm / minute. Bead width, which is the diameter of the pulse irradiation area (spot) (Fig. 2
W × 2) is about 0.7 mm (diameter of melting area by pulse). As a result, the laser welding of the fitting portion 3 is completed and sealing is performed. The material of the rectangular case may be a stainless steel plate or the like. C in FIG. 2 is the spot center of the laser beam, m is the end position of the bead,
w indicates the distance from the center of the laser beam to the bead end position.

Here, the spot center is offset from the fitting portion 3 to the lid plate 2 side, the offset amount (mm) is variously changed, and the sagging to the outside of the welding area, that is, the penetration area 5 and the penetration depth are examined. It was The evaluation of the sagging to the outside of the rectangular case 1 was measured using a digital caliper. Penetration depth a of the welded part in the fitting part 3 (see FIG. 2)
Was evaluated by cutting the cross-section and up to what percentage of the plate thickness of the lid was melted.

The results are shown in FIG. The thickness t1 of the side surface of the case was 0.3 mm, and the thickness t2 of the cover plate 2 was 0.6 mm. When the offset amount is 0, the melt-in ratio is sufficient as shown in FIG. 8, but the amount of sagging to the outside of the case is large and the outer dimensions of the case do not meet the standard. If the offset amount is increased to about 0.2 times the plate thickness difference (t2-t1) or more, the sagging amount hardly occurs. Further, if the offset amount is further increased, there will be no problem for who, but since the penetration depth a at the abutting portion will decrease, the welding strength will decrease.
When the offset amount is 0.8 times the plate thickness difference, the penetration rate becomes 50%. Here, the penetration rate means a / t2 in FIG. Therefore, in order to secure the penetration rate of 50% or more, the offset amount may be 0.8 times or less of the plate thickness difference.

(Control Example 1) Next, a control example of the present embodiment using the laser welding machine of FIG. 1 will be described with reference to the flowchart of FIG. This flow chart is for controller 8
It is carried out by. The controller 8 controls the center of the laser spot (objective lens 7
It is assumed that the X and Y tables 6 are controlled so that the focal point (0) moves sequentially along the fitting portion 3 of the battery assembly 100. Since such control itself is not the gist of the present invention, its detailed description is omitted.

First, it is checked whether or not the spot center of the laser beam (focal position of the objective lens 70) is currently running (scanning) (that is, whether the X, Y table 6 is driven by a predetermined program). (100), otherwise, wait, and if so, the current coordinate position of the spot center of the laser beam from the built-in program or the position sensor (not shown) of the X, Y table 6 (hereinafter referred to as the current position) Is input (102). Alternatively, instead of using the position sensor, the current position may be read from a traveling program stored in the ROM in advance. It should be noted that this traveling program is incorporated so that the spot center of the laser beam travels on the fitting portion 3.

Next, based on the detected current position and the built-in running program, the coordinates of the offset point which is separated from the current position by a predetermined small distance and is located inside the fitting portion 3 by a predetermined offset distance Lx. (X, Y coordinates) is calculated as the next position (106), the distance vector from the current position to this next position is calculated (107), and only the distance vector opposite to this distance vector, that is, the direction with the same magnitude, The X, Y table 6 is moved by the opposite distance vector (108).

In this way, the inside of the shape of the fitting portion 3 stored in the running program can be smoothly traveled by a constant offset distance, and good welding can be performed. It is needless to say that the controller 8 commands the laser oscillator 7 to emit at the set or constant firing interval with the set or constant laser output.

(Control Example 2) A modified example of the above control example will be described below. In the vicinity of the corner portion 32 of the fitting portion 3, the inner portions of the respective spots of the laser beam overlap each other, so even if the spot center of the laser beam is focused on the corner portion 32 under the condition that the scanning speed is constant and the irradiation interval is constant, it is the highest. The penetration depth point naturally offsets inward. This fact indicates that the best result should be obtained by adjusting the offset distance Lx in the control example 1 by the natural offset amount at the corner portion 32.

This control example is based on the above findings, and will be described below with reference to the flow chart shown in FIG. Since this flowchart is obtained by adding steps 103 to 105 to the flowchart shown in FIG. 5, only steps 103 to 105 will be described. First, it is checked whether or not the spot of the laser beam (focal point of the lens 70) is currently traveling in the vicinity of the corner 32, that is, whether or not the vehicle is turning (103). If not, the offset distance Lx is set to a constant value Lc. Set (104) otherwise R based on current position offset distance Lx
It is read from the table built in the OM (105).

The relationship between the current position and the offset amount near the corner 32 is stored in this table. That is, when the bending is started from the side portion 31 along the corner portion 32, the offset amount is set to a value obtained by gradually reducing the constant value Lc, and thereafter, the bending end approaching from the corner portion 32 to the next side portion 31 is finished. As L approaches, the above constant value L
If the offset amount is set to a value that gradually increases the constant value Lc as the corner portion 32 approaches the next side portion 31, the offset amount is continuously changed. Therefore, the jump of the traveling locus of the center of the spot of the laser beam does not occur, and the substantial offset amount at the corner portion 32 (the distance from the point where the penetration depth is maximum to the fitting portion 3) is fitted. It can be constant over the entire circumference of the part 3.

At the corner 32 of the fitting portion 3, the distance between the spot centers of adjacent laser beams is shortened (they come close to each other) due to the curvature, so that the maximum penetration depth increases. To do. Therefore, step 103
If it is found that the vehicle is turning around the corner 32,
In step 105, it is preferable to slightly reduce the power per spot of the laser beam.

Alternatively, instead of performing the control shown in the flow chart of FIG. 6, for example, when irradiating the corner portion 32 of the fitting portion 3 with a laser beam spot, compared to the case of irradiating the side portion 31, The penetration depth at the corner portion 32 may be reduced by weakening the laser irradiation energy or increasing the beam scanning speed. (Modification) In the above embodiment, the laser oscillator 7 is fixed and the X, Y table 6 is driven to scan the spot of the laser beam. However, in addition, the battery assembly 100 is fixed and the laser oscillator 7 is fixed. Obviously, it may be driven horizontally. An example of driving the laser oscillator 7 will be described below.

First, the rectangular case 1 has a width of 16 mm, a length of 7.5 mm, a height of 83.5 mm, and a thickness of 0.3.
It is formed by forming a nickel-plated steel sheet of mm. The cover plate 2 is
Horizontal 15.4 mm, vertical 6.9 mm, thickness 0.6 mm
It is formed by forming a nickel-plated steel sheet. The laser pulse is emitted at an interval of 100 pieces / sec, the scanning speed of the laser beam along the fitting portion 3 is 500 mm / min, and the bead width, which is the diameter of the pulse irradiation area (spot) (see FIG. 2).
W × 2) is about 0.7 mm (the diameter of the pulse irradiation area). The laser beam is scanned by a 6-axis robot (not shown). As a result, the laser welding of the fitting portion 3 is completed and sealing is performed. The material of the square case is
You may use a stainless steel plate etc.

[Brief description of drawings]

FIG. 1 is a schematic perspective view illustrating a method of welding a rectangular battery case using a laser welding machine.

FIG. 2 is a vertical cross-sectional view of a welded portion of a rectangular case using the method of this embodiment.

FIG. 3 is a perspective view showing an example of a closed container of a prismatic battery to which the method of this embodiment is applied.

FIG. 4 is a graph showing the relationship between the offset amount of the spot center of the laser beam with respect to the fitting portion of the plate, the sagging amount to the outside of the case, and the penetration rate.

FIG. 5 is a flowchart showing a welding control example 1 of the embodiment.

FIG. 6 is a flowchart showing a welding control example 2 of the embodiment.

FIG. 7 is a vertical cross-sectional view of a welded portion of a conventional rectangular case.

FIG. 8 is a vertical cross-sectional view of a welded portion of a conventional rectangular case.

[Explanation of symbols]

1 is a rectangular case (metal case), 2 is a cover plate, and 3 is a fitting part.

Claims (4)

[Claims] 1. A method of manufacturing a prismatic battery, wherein a lid plate made of a metal plate is fitted into a prismatic opening formed at one end of a metal case, and the fitting portions are sequentially laser-welded to form a prismatic battery container. A method for manufacturing a prismatic battery, wherein a spot center of a laser beam is offset inside the fitting portion. 2. A manufacturing method of a prismatic battery in which a fitting portion of a metal case having a rectangular cross section having a battery element inside and a metal lid plate which is fitted into an opening of the case and closes the case is joined by laser welding. In the method, a planar form of the fitting portion is formed into a linear shape composed of a linear side portion and a curved corner portion connecting a pair of adjacent side portions, and the fitting portion is formed over the entire circumference. A method for manufacturing a prismatic battery, wherein the laser welding is performed by aligning a spot center of a laser beam on a scanning path set at a position offset inward by a predetermined dimension range from the fitting portion. 3. A battery assembly including the case and the cover plate fitted in the opening of the case is mounted on a mounting surface of an X, Y table, and the irradiation position of the laser beam is in front. A laser oscillator is arranged above the table so as to be fixed at a predetermined position on the placing surface, and the laser is driven by driving the table in the X coordinate direction and the Y coordinate direction which are parallel to the placing surface and orthogonal to each other. 3. The method for welding a rectangular battery container according to claim 1, wherein the spot center of the beam is moved along a scanning path set at a position offset inward by a predetermined dimension range from the fitting portion. 4. The method for manufacturing a prismatic battery according to claim 1, wherein the lid plate is fitted into the opening of the case by press fitting.