JP2003208876A - Square battery can and manufacturing method thereof, and square battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a square battery can improved in productivity by reducing the number of process even in the case of using a DI method and having a high energy density and a required pressure proof strength, and to provide a manufacturing method thereof and a square battery using the same. <P>SOLUTION: This square battery can manufacturing method has a first process for impact-extruding a predetermined shape pellet 7 to form an intermediate cup body 8 having a nearly elliptic cross sectional shape, and a second process for forming square battery cans 9 and 21 having a nearly rectangular cross sectional shape by using the DI method for continuously and concurrently performing drawing and ironing. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectangular battery can used as an outer casing of various rectangular batteries such as a lithium ion secondary battery, which is continuously subjected to DI (drawing and ironing, that is, both drawing and ironing). The present invention relates to a manufacturing method that can be manufactured by using the manufacturing method and a rectangular battery that is configured by using a rectangular battery can obtained by the manufacturing method.

[0002]

2. Description of the Related Art In recent years, along with the progress of electronic technology, it has become possible to reduce the size and weight of the electronic equipment and reduce the power consumption as well as the functionality of the electronic equipment. As a result, various consumer portable devices have been developed and put into practical use, and the market size of them has been expanding rapidly. Typical examples thereof include camcorders, notebook computers, mobile phones, and the like. These devices are continuously required to be smaller and lighter and have a longer operating time.
From such a demand, as a built-in power source for driving these devices, a lithium secondary battery typified by a lithium ion secondary battery having a long life and a high energy density has been actively developed and adopted in large numbers.

The lithium ion secondary battery is a unit used as an index for reducing the weight of the battery, as well as the energy density per unit volume used as an index for reducing the size of the battery, among the battery systems currently in practical use. It has the advantage that the energy density per weight is extremely high. The energy density of the battery is mainly determined by the positive and negative battery active materials that constitute the power generation element, but downsizing and weight reduction of the battery can that houses the power generation element are also important factors. That is, if the battery can can be made thin, more battery active material can be accommodated in the battery can of the same outer shape to improve the volume energy density of the entire battery, and if the battery can can be made of a lightweight material, the entire battery can be And the weight energy density is improved.

Among the battery trends described above, in particular,
A prismatic battery using a thin prismatic battery can as an outer case is more important than a cylindrical battery because it is suitable for thinning a device and has high space efficiency. Conventionally, as a method of manufacturing a prismatic battery can, by repeating deep drawing using a transfer press machine for 10 or more steps,
A so-called transfer drawing method for manufacturing a battery can whose cross-sectional shape is substantially rectangular, or a method by impact molding using aluminum as a material has already been adopted.

[0005]

However, in the production of prismatic battery cans using the transfer drawing method, since deep drawing is repeated ten or more times, the productivity is very poor, for example, about 20 pieces / min. However, since the number of steps is large and the die for multistage drawing is complicated, there is a drawback that the cost becomes high. Furthermore, in the transfer drawing method, when the wall thickness of the battery can material is thinned for the purpose of increasing the volumetric energy density and increasing the capacity, the deep drawing is repeated to reduce the thickness. It is necessary to pull in and out the punch, and to reduce the punch diameter each time, and also to reduce the clearance with the die, it is necessary to make the thick part around the bottom as thin as the side. Is very difficult to draw. Further, the prismatic battery can thus obtained has a problem that the strength of the peripheral portion of the bottom is insufficient and the required pressure resistance strength cannot be secured when it functions as a battery.

Conventionally, a rectangular battery can (see Japanese Patent Laid-Open No. 2000-182573) in which the can thickness of the long side plate is set larger than that of the corner part, and the can thickness of the long side plate is short. There is proposed a prismatic battery can (see Japanese Patent Laid-Open No. 6-52842) in which the thickness of the can is set larger than that of the side plate portion. However, these prismatic battery cans can prevent bulging deformation of the long side plate when the internal pressure of the battery rises, but since the can thickness of the long side plate having the largest surface area is increased, Since the volume for accommodating is small, the volume energy density and the weight energy density cannot be improved.

Further, in the past, a battery can (a battery can whose internal resistance is reduced by forming a fine vertical line perpendicular to the bottom surface on the inner surface of the can to increase the contact area with the power generating element) JP-B-7-99686 and JP-A-9-2
(See each publication of 19180) is also known. But,
The vertical streaks of these battery cans hardly provide the function of preventing bulging and deformation when the battery internal pressure rises. Further, conventionally, there is also proposed a prismatic battery can in which the can thickness of the corner portion is set to be larger than the can thickness of the long side plate portion and the short side plate portion, which are straight portions (see Japanese Patent Laid-Open No. 7-326331). . Although this prismatic battery can can improve the storage rate of the power generation element, the bulging deformation of the thin long side plate cannot be prevented only by increasing the strength by the thickened corner.

On the other hand, in the production of a prismatic battery can by impact molding, the pellets, which are the material for the battery can, are crushed by the punch and the material is pushed into the gap between the punch and the die to extend along the outer peripheral surface of the punch. As a result, a prismatic battery can can be formed, so that the productivity is improved as compared with the transfer drawing step, but the dimensional accuracy is extremely poor, and when the wall thickness is reduced, the strength of the side surface portion becomes insufficient. In particular, in the case of a prismatic battery can, when it functions as a battery, the deformation when the internal pressure of the battery rises is larger than that of a cylindrical battery can, which has a stable shape, and a cylindrical shape with a more stable shape. Since the long side plate having a large area is deformed so as to bulge, the device may be damaged due to electrolyte leakage or short circuit of the power generation element. Therefore, in the production of prismatic battery cans by impact molding, in order to ensure strength that can reliably prevent deformation when the internal pressure of the battery rises, it is necessary to sacrifice the thinning and weight reduction without fail, and the volume energy It is not possible to improve the density and the weight energy density.

In addition to the above, as another method of manufacturing a prismatic battery can, it is also proposed to separately form a square tube and a bottom plate and to hermetically join the bottom plate to the bottom of the square tube by laser welding. (See JP-A-6-333541). However, in this manufacturing method, the number of steps is not so much reduced as compared with the transfer drawing step, and moreover, laborious work such as accurate positioning step between the rectangular tube and the bottom plate and laser welding step are involved, which results in a high productivity. Cannot improve. Moreover, with this manufacturing method, it is not possible to obtain a prismatic battery can that simultaneously satisfies the contradictory requirements of high energy density due to thinning and weight reduction and pressure resistance that does not deform when the battery internal pressure rises.

By the way, in the method of manufacturing a battery can of a cylindrical battery, it is possible to manufacture a battery can which is thin and has a required pressure strength while improving the volumetric energy density, and which can be manufactured with high productivity. A possible DI method is used. This DI method is a method of continuously performing drawing and ironing on a cup-shaped intermediate product manufactured by deep drawing using a press machine, thereby manufacturing a predetermined cylindrical battery can. Compared with the transfer drawing method, productivity is improved by reducing the number of processes, dimensional accuracy such as wall thickness is improved, weight reduction by reducing the wall thickness of the can side peripheral wall, and energy density improvement with capacity increase Its advantages include the reduction of stress corrosion, and its use is expanding.

Therefore, it can be considered to manufacture a prismatic battery can by the above-mentioned DI method. However, when a cylindrical battery can is manufactured by the DI method, it is a similar process from a cup-shaped intermediate product having a circular cross-sectional shape to a battery can having the same horizontal cross-sectional shape. Since the wall thickness of the entire peripheral wall is uniformly reduced in the process, the material flows uniformly during processing and is smoothly deformed. On the other hand, if a prismatic battery can is manufactured only by DI processing, a cup-shaped intermediate product with a circular cross-section will be transformed into a battery can with a substantially rectangular cross-section. Since the material flow is uneven, eccentricity tends to cause uneven thickness, shearing, cracks, etc., and the processing stress that acts during molding is not uniform, making it difficult to process due to stress concentration, and stable processing cannot be performed. Therefore, it is difficult to perform high-precision molding, and in particular, a short side plate portion having a small area in a square is likely to be cracked or fractured, and a problem such as a distorted portion is generated.

Therefore, after forming the first intermediate cup body by drawing, the side peripheral wall portion of the intermediate cup body is repeatedly drawn several times to form the second intermediate cup body, and finally the first intermediate cup body. A method of manufacturing a prismatic battery can in which the can thickness of the bottom plate portion and the corner portion is adjusted to a predetermined value by impact-extruding (impact molding) the intermediate cup body of No. 2 is proposed (see JP-A-10-5906). Has been done. However, in this manufacturing method, drawing and multi-stage D
Since I processing and impact molding are required, the number of processes increases, and since the bottom plate is adjusted to have a desired can thickness by impact molding in the last process, the bottom plate and the side peripheral wall can be formed. Adjustment of the can thickness becomes very difficult, and it is not possible to obtain a prismatic battery can with a required can thickness in each part with high accuracy.

On the other hand, the applicant of the present application has previously proposed a manufacturing method capable of manufacturing a prismatic battery can having a high energy density and a required pressure resistance strength by using the DI method (Japanese Patent Application No. Hei 10 (1999) -135242). 11-126873). In this manufacturing method, the hoop material is punched in the first step,
After forming the oval-shaped battery can material 1 as shown in (a), the battery can material 1 is deep-drawn, and then the battery can material 1 shown in FIG.
The first intermediate cup body 2 having a substantially elliptical cross-section as shown in FIG. Next, the first intermediate cup body 2 is subjected to a plurality of stages of continuous redrawing by the second step using a drawing press machine, and then, as shown in FIG. Shorter diameter than the cross-sectional shape of body 2 /
The second intermediate cup body 3 having a substantially elliptical cross-sectional shape with a small major axis ratio is formed. Finally, in the third step, the second intermediate cup body 3 is subjected to DI processing in which drawing and ironing are continuously performed, so that FIG.
As shown in FIG. 3, the rectangular battery can 4 having a substantially rectangular cross-section is formed, and the thickness of the short side plate 4a is larger than that of the long side plate 4b.

In this manufacturing method, since the rectangular battery can 4 having a desired shape can be manufactured in three steps, the productivity is remarkably improved as compared with the conventional transfer drawing method and the DI method is used. Thus, the rectangular battery can 4 having high dimensional accuracy such as wall thickness can be obtained. However, this manufacturing method still has a problem to be solved. That is, when an attempt is made to manufacture a prismatic battery can by suddenly subjecting the first intermediate cup body 2 to DI processing, the cross-sectional shape is changed from a substantially elliptical shape close to a circle to a substantially rectangular shape.
Since I processing is performed, breakage and cracks occur. Therefore, it is necessary to intervene in the second step. In the second step, the material is deformed due to the drawing while reducing the dimension in the minor axis direction by narrowing so that the minor axis gradually becomes shorter. Is flowed so as to escape in the major axis direction, and the major axis direction is shortened to a predetermined dimension for correction. Therefore, in the second step, redrawing is performed in a plurality of stages, so that the number of steps increases.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and it is possible to reduce the number of steps and improve the productivity while using the DI method, and it is possible to achieve high dimensional accuracy and high productivity. It is an object of the present invention to provide a prismatic battery can having an energy density and a required withstand pressure strength, a method of manufacturing the prismatic battery can that can easily obtain the prismatic battery can, and a prismatic battery using the prismatic battery can. is there.

[0016]

In order to achieve the above object, a method of manufacturing a prismatic battery can according to a first invention is a first method for forming an intermediate cup body by impact molding a pellet having a predetermined shape. And a second step of molding the intermediate cup body into a rectangular battery can having a substantially rectangular cross-sectional shape by DI processing in which drawing and ironing are continuously performed at once. It is characterized by being.

In this method of manufacturing a prismatic battery can, an intermediate cup body having a substantially rectangular transverse cross section is manufactured at once by impact molding capable of manufacturing an arbitrary shape in one step, and the intermediate cup body is formed into a rectangular shape by a DI method. Since it is processed into a battery can, both have only the first and second steps that can be formed only by moving the stroke of the punch, and the number of steps is significantly reduced, and the productivity is significantly improved. Further, since the intermediate cup body is processed by DI, a rectangular battery can having a desired shape can be easily and surely manufactured, and dimensional accuracy such as wall thickness is improved, so that the wall thickness can be made as thin as possible. It is possible to manufacture a prismatic battery can having excellent pressure resistance.

Regarding the shape of the cross section of the intermediate cup body, one having R at the four corners of the rectangle, one having long sides parallel and one having short sides R-shaped, and an elliptical shape having a substantially rectangular shape are provided. It can be used and preferably has a plan view shape corresponding to the outer shape of the cross-sectional shape of the prismatic battery can to be manufactured.

In the method for manufacturing a prismatic battery can according to the second aspect of the present invention, the first step of impact-molding pellets having a predetermined shape to form an intermediate cup body, and the intermediate cup body are crossed in a rectangular shape. Using a DI punch in which processing grooves are formed in a grid pattern on at least long side surfaces of a rectangular plate material having a surface shape, drawing and ironing are continuously performed at once.
By processing I, a plurality of ridge bulges having a rectangular cross-sectional shape and bulging at least on the inner surface of the can of the long-side side plate so that the thickness direction becomes thick and linearly extending. And a second step of forming a prismatic battery can whose parts are formed in a grid arrangement.

In this method for manufacturing a prismatic battery can, in addition to the same effects as the first invention, the second step D
In the I machining, since a part of the material on the inner surface side of the can of the intermediate cup body enters the processing groove of the DI punch while being plastically deformed, the material on the inner surface side of the can of the intermediate cup body creates a resistance between the material and the DI punch. As it is added, it moves integrally with the DI punch, and the material on the outer surface side of the can of the intermediate cup body is mainly squeezed by the die.
It is possible to suppress the phenomenon of material surplus with the I-punch and smooth the material flow. Further, by forming the ridge bulge portion only on the long side plate portion of the prismatic battery can, the processing speed at the long side plate portion can be suppressed, and the entire processing speed can be made constant. As a result, according to this manufacturing method, it is possible to manufacture a prismatic battery can having a uniform can thickness in which a wavy shape does not occur on both the inner surface and the outer surface of the can. Furthermore, the can-shaped prismatic battery can is made as thin as possible, and has a strength that can effectively suppress bulging deformation by virtue of the lattice-shaped convex bulging portion functioning as a reinforcing crosspiece. It has an extremely high pressure resistance.

In the second aspect of the invention, DI machining is performed using a DI punch engraved in a state in which a plurality of machining grooves forming a lattice are communicated with each other through intersections intersecting each other, and each intersection is formed. It is preferable to form a plurality of convex bulging portions on the inner surface of the can, which form a lattice shape and are connected to each other via. Thus, the prismatic battery can thus manufactured has an extremely high pressure resistance strength because the direction in which the strength increases due to the convex bulging portion is two or more directions.

A method of manufacturing a prismatic battery can according to a third aspect of the present invention comprises: a first step of impact molding a pellet having a predetermined shape to form an intermediate cup body;
A second step of forming a prismatic battery can body having a substantially rectangular cross-section by a DI process in which a drawing process and an ironing process are continuously performed all at once, and a square plate material is formed on the battery can body. A third step of press-fitting a machining core having machining grooves formed in a grid pattern on at least the long side plate portion, and pressing a pressing member over the entire outer surface of the long side plate portion on both sides of the battery can body. By applying and pressurizing, a part of the material on the inner surface of the can of the battery can body is plastically deformed so as to enter the working groove, and the inner surface of the can is projected in a lattice-shaped convex strip corresponding to the working groove. And a fourth step of transferring and forming the projecting portion.

In this method of manufacturing a prismatic battery can, in addition to the same effects as the first invention, the battery can equivalent to the battery can obtained by the second invention can be manufactured by simple steps. You can

In each of the above inventions, it is preferable that after the battery can material or pellets of the battery can material formed into a predetermined shape are annealed, the pellets are impact molded. As a result, the extensibility of the pellets during impact molding becomes good, and the intermediate cup body obtained by impact molding has a small variation in the wall thickness of its side surface portion.

Further, in each of the above inventions, it is preferable that the intermediate cup body obtained by impact molding is annealed and then the intermediate cup body is subjected to DI processing. As a result, the intermediate cup body has the advantage that the work hardening caused during impact molding is mitigated and the elongation of the material is improved, so that the DI processing is facilitated.

Further, in each of the above inventions, the pellets are subjected to impact molding so that the ratio of the thickness of the long side plate / the thickness of the bottom plate is 0.6 to 1.3, and the thickness of the short side plate / the bottom plate. It is preferable to mold an intermediate cup body having a shape having a thickness ratio of 1.0 to 1.8.

An intermediate cup body having a long side plate and a short side plate having a small thickness requires less processing load at the time of DI processing, but on the other hand, it is difficult to control to obtain a battery can having a required thickness. The intermediate cup body, which has a thick short side plate,
Control can be easily performed to obtain a battery can having a required can thickness, but the processing load during DI processing becomes large. Therefore, in the intermediate cup body, the ratio of the thickness of the long side plate / the thickness of the bottom plate is 0.6 to 1.3, and the thickness of the short side plate /
If the bottom plate portion is formed in a shape having a thickness ratio within the range of 1.0 to 1.8, the processing load for DI processing of this intermediate cup body is reduced, and a battery having a required thickness is obtained. The control for obtaining the can is facilitated, and in particular, the occurrence of tearing at the long side plate portion can be reliably prevented.

Further, in each of the above inventions, the pellets are impact-molded to form a bottomed rectangular tube having a substantially rectangular cross section, and the long side plate portion, the short side plate portion and the corner portion are formed in this order. It is preferable to form an intermediate cup body having a shape with a large plate thickness.

As a result, the intermediate cup body is D
I When machining, the long side plate, the short side plate and the corner except the bottom plate are squeezed at almost the same ratio, so that the occurrence of defects such as tearing and tearing can be reliably prevented, while the long side plate It is possible to reliably obtain a battery can having a required shape in which the plate portion, the short side plate portion, and the corner portion have a large plate thickness in this order.

Furthermore, in each of the above inventions, it is preferable that the pellets are made of aluminum or aluminum alloy. As a result, the impact molding in the first step can be smoothly performed with a material having good stretchability.

In each of the above inventions, the pellets are
It is preferable to form an oval shape or a substantially rectangular shape having a shape in plan view corresponding to the outer shape of the cross-sectional shape of the prismatic battery can to be manufactured. As a result, when the pellet has an oval shape, it is possible to prevent the shape from being crushed due to the stress generated at the time of impact molding, and to reliably form the intermediate cup body into a required shape. On the other hand, when the pellet is formed into a substantially rectangular shape, an intermediate cup body having an outer shape similar to that of the rectangular battery can to be formed can be formed.
The processing load when manufacturing a predetermined prismatic battery can by I processing is reduced.

The prismatic battery can of the present invention is manufactured by any one of the above-mentioned manufacturing methods and is a bottomed rectangular tube having a substantially rectangular cross section, and its long side plate and short side plate. It has a shape in which the thickness of each can increases in the order of the portion and the corner.

As a result, when the internal pressure of the battery rises, the force for bulging and deforming the long side plate portion and the force for indenting the short side plate portion act simultaneously. On the other hand, the short side plate part having a can thickness larger than that of the long side plate part effectively prevents outward expansion of the long side plate part. Also, the long side plate part tries to bulge and deform outward with the corner part as a fulcrum, so the corner part with a larger can thickness than the short side plate part bulges outward from the long side plate part. Effectively block. Therefore, while the long side plate portion is set to have the smallest can thickness, it is effectively prevented from expanding and deforming outward as the battery internal pressure rises, and sufficient pressure resistance can be secured. The volume of the power generating element can be increased by minimizing the can thickness of the long side plate having the largest surface area in the peripheral wall portion. In particular, in the case of forming a grid-shaped convex bulging portion on the long side plate portion, the convex bulging portion can effectively suppress bulging deformation, so that the can thickness of the long side plate portion can be minimized. Can be thin. Further, even if the can thickness of the corner portion is thickened in a shape in which it is swollen inward by the amount of the voids formed between the corner portion and the electrode group housed in the battery can, the capacity of the electrode group is not reduced.

It can be manufactured by any of the methods for manufacturing a prismatic battery in which the convex bulging portion is formed on the inner surface of the can in each of the above inventions, and the can thickness of the long side plate can be set to 0.25 mm or less. That is, since the long side plate portion is effectively restrained from bulging and deforming by the lattice-shaped convex bulging portion,
It is possible to form a can thickness as small as 0.25 mm or less. In other words, in this battery can, the problem that the bulging deformation is likely to occur when the can thickness of the long side plate is reduced to 0.25 mm or less has been solved by forming the grid-shaped ridge bulge. It is a thing.

The prismatic battery of the present invention uses a prismatic battery can manufactured by any one of the methods for manufacturing a prismatic battery of the above invention, and the power generating element is housed inside the prismatic battery can and the opening is provided. It is configured by liquid-tightly sealing with a sealing body.

This prismatic battery has improved productivity because the prismatic battery can can be manufactured in a small number of steps, and the prismatic battery can can be formed with a thin wall thickness as high as possible with high dimensional accuracy. By forming it, it becomes possible to have sufficient pressure resistance while improving the volume energy density.

In the method for manufacturing a prismatic battery can according to the above invention, it is preferable that the pellet is impact-molded by using a punch having an uneven surface to mold the intermediate cup body. As a result, when the tip surface of the punch comes into contact with the pellet at a predetermined relative position, the unevenness of the tip surface of the punch bites into the surface of the pellet, and the punch is displaced relative to the pellet in the subsequent impact molding process. The intermediate cup body is molded while being held at a predetermined relative position without performing. Therefore, since the material flows evenly and smoothly around the punch as the pellets are deformed, the intermediate cup body having no uneven thickness can be reliably formed.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will now be described in detail with reference to the drawings. First, the manufacturing process in the manufacturing method of the prismatic battery can of the first embodiment will be schematically described. In this method for manufacturing a prismatic battery can, in the first step shown in the schematic vertical sectional view of FIG. 1, as shown in FIG. 3, the pellet 7 as a battery can material has a cross-sectional shape of the prismatic battery can to be manufactured. It is formed in a plan view shape corresponding to the outer shape of FIG. By impact molding the pellets 7, an intermediate cup body 8 having a substantially elliptical cross-sectional shape with a small minor axis / major axis ratio shown in FIG. 2B or a substantially rectangular shape shown in FIG. Forming an intermediate cup body 8 having a cross-sectional shape of
In the second step shown in the schematic longitudinal sectional view of FIG.
By processing, the rectangular battery can 9 having a desired shape shown in the partially broken perspective view of FIG. Below, the first
The second step will be sequentially described in detail.

When the pellet 7 has an oval shape,
It is possible to prevent the shape of the intermediate cup body 8 from being crushed due to the stress generated at the time of impact molding, and to reliably form the intermediate cup body 8 into a desired shape. On the other hand, when the pellet 7 has a substantially rectangular shape, the intermediate cup body 8 having an outer shape close to that of the rectangular battery can 9 to be formed can be formed.
The processing load when the predetermined prismatic battery can 9 is manufactured by DI processing is reduced.

FIG. 1 shows a press machine for performing impact molding in the first step, in which the die 1 is attached to the die holder 10.
1 is fixed. Pellets 7 as a battery can material shown in FIG. 3A or FIG. 3C are supplied to the processed holes 11 a of the die 11. The pellet 7 is made of aluminum or an aluminum alloy because it can reduce the weight of the prismatic battery can 9 to be manufactured and has the extensibility required for impact molding in the first step. To use. In particular, the aluminum alloy preferably contains manganese. In particular,
An aluminum alloy having a chemical composition of JIS standard H4000 A1000 to A5000 is used. Such an aluminum alloy has a malleability which is extremely suitable for impact molding, and can obtain a preferable work hardening after molding. More preferably, an aluminum alloy having a chemical composition of A3000 is used, and in this case, the characteristics as a battery can are excellent.

Further, the pellet 7 is formed by punching out the battery can material made of the above-mentioned aluminum or aluminum alloy so as to have a plan view shape as shown in FIG. It is formed in an oval shape having an elliptical shape close to the surface shape or in a substantially rectangular shape shown in FIG. The pellet 7 having such a shape is annealed at a temperature of 250 ° C. to 400 ° C. for 0.5 hours to 3 hours (preferably about 1 hour). This annealing treatment may be performed on the battery can material before punching the pellet 7, but it is preferable to perform it on the pellet 7 obtained by punching.

The pellet 7 is the processing hole 11 of the die 11.
When inserted into a, as shown in FIG. 1B, the punch 13 held by the punch holder 12 is moved closer to the die 11 side and is driven into the processing hole 11a of the die 11. As a result, the pellets 7 are crushed by the punch 13 and expanded so as to be pushed into the gap between the punch 13 and the hole wall of the processing hole 11a, while being extended along the outer peripheral surface of the punch 13. Is cast into.

In the above impact molding, the uneven surface 13a formed on the tip surface of the punch 13 bites into the surface of the pellet 7 when it comes into contact with the pellet 7, so that the punch 13 can be used by the punch 13 in the subsequent impact molding process.
It is held at a predetermined relative position without being displaced. Therefore, the pellets 7 that deform as the processing progresses
Since the material of (3) flows evenly and smoothly around the punch 13, the highly accurate intermediate cup body 8 without uneven thickness can be surely molded. The uneven surface 13a is preferably formed in a mesh shape like a knurl. Further, the uneven surface 13a is not always necessary, and it is possible to obtain an intermediate cup body having a substantially required shape by impact molding with a punch having a flat tip surface. When the punch 13 has finished moving by a predetermined stroke,
The intermediate cup body 8 having the shape shown in FIG. 3 (b) or FIG. 3 (d) is molded. On the bottom surface of the intermediate cup body 8, an uneven surface 8d to which the uneven surface 13a of the punch 13 is transferred is formed. Since the intermediate cup body 8 is obtained by impact molding the pellet 7 which has been subjected to the above-mentioned annealing treatment and has a good elongation, the intermediate cup body 8 also has a side surface. The variation in the wall thickness of the portion is further reduced.

The intermediate cup body 8 has substantially the same shape as the second intermediate cup body 3 shown in FIG. 5 (c), and has a desired cross-sectional shape of a substantially elliptical shape or a substantially rectangular shape. There is. Therefore, this manufacturing method is equivalent to the second intermediate cup body 3 manufactured through the first step of deep drawing and the second step of redrawing in the manufacturing method of the above-mentioned prior application. The intermediate cup body 8 can be molded at once by performing the impact molding in the first step. However, since the intermediate cup body 8 is formed in one step by impact molding, there are some portions that are deformed into strain, but this is sufficiently corrected in the DI method in the second step described later. I can, so there is no problem.

Next, as shown in FIG. 1 (c), the punch 13 which has finished moving by a predetermined stroke has the die 11
Away from and move toward the original position. At this time, the molded intermediate cup body 8 is removed from the punch 13 by the stripper 14 after being pulled out from the processing hole 11 a by the punch 13 while being attached to the punch 13.

By the way, in the DI process of the second step, which will be described later, the stress that the material tends to collect in the central direction acts, and thus the obtained battery can tends to have a crushed shape. On the other hand, in this embodiment, pellets 7 which are previously formed in an oval shape or a rectangular shape are impact-molded to form an intermediate cup body 8 having a substantially elliptical shape or a substantially rectangular cross-sectional shape. Is subjected to DI processing, it is possible to mold a battery can having a required shape while preventing crushing due to stress or reducing the processing load.

The thickness of the intermediate cup body 8 is equal to that of the punch 13
And the hole wall of the processing hole 11a of the die 11 are arbitrarily set. Intermediate cup body 8 with thin side wall
Although the processing load at the time of DI processing in the post process is small, it is difficult to control to obtain a battery can having a required wall thickness, and conversely, the intermediate cup body 8 having a thick side wall is required. Although the control for obtaining the battery can 9 having the wall thickness can be easily performed, the processing load at the time of DI processing becomes large. Therefore, in the intermediate cup body 8, the ratio of the thickness of the long side plate portion / the thickness of the bottom plate portion is 0.6 to 1.3, and the ratio of the thickness of the short side plate portion / the thickness of the bottom plate portion is 1.0 to 1. If the intermediate cup body 8 is formed to have a shape within the range of 0.8
The processing load at the time of processing is reduced, and the control for obtaining the battery can 9 having a required wall thickness is facilitated, and in particular, the occurrence of troubles such as tearing of the long side plate portion can be reliably prevented.

Even when the intermediate cup body 8 is obtained by impact-molding the battery can material or the pellet 7 which has been subjected to the above-mentioned annealing treatment, it can be subjected to the annealing treatment again and then subjected to DI processing. preferable. This annealing treatment is performed at a temperature of 250 ° C. to 400 ° C. for 0.5 hours to 3 hours (preferably about 1 hour). As a result, the intermediate cup body 8 relaxes the work hardening that has occurred during impact molding, improves the extensibility of the material, and makes it easier to perform the DI process in the next step.

Then, the intermediate cup body 8 is processed by the drawing and ironing machine in the second step shown in FIG.
A rectangular battery can 9 having a desired shape is formed by DI processing in which a step drawing process and a three-step ironing process are continuously performed at once.
Becomes This drawing and ironing machine is equipped with
7, a die mechanism 18, a stripper 19 and the like. The die mechanism 18 includes a drawing die 18
A and the first to third ironing dies 18B to 18D
And the dies 18A to 18D are arranged in series so as to be concentric with the axis of the DI punch 20.

The intermediate product conveying section 17 sequentially conveys the intermediate cup body 8 to the molding location. The intermediate cup body 8 conveyed to the molding location and positioned is driven by a DI wheel 20 driven by a flywheel (not shown),
The drawing die 18A draws the shape so as to conform to the outer shape of the DI punch 20. The cup body that has finished passing through the drawing die 18A is the intermediate cup body 8
On the other hand, each dimension in the major axis direction and the minor axis direction is slightly smaller,
Moreover, it is deformed into a body length and molded into a substantially elliptical shape close to a substantially rectangular cross-sectional shape of the desired prismatic battery can 9, but there is no change in its wall thickness or the like.

Next, the cup body which has finished passing through the drawing die 18A is pushed by the DI punch 20, and
The first ironing die 18B performs the first step of ironing, the side peripheral portion is expanded and the thickness thereof is reduced, and the hardness is increased by work hardening. The cup body that has finished passing through the first ironing die 18B has a second ironing die 18C having an ironing hole smaller than that of the first ironing die 18B, and then the DI ironing die 20C. By the third ironing die 18D having an ironing hole smaller than the second ironing die 18C, the second and third steps of ironing are sequentially performed, and the peripheral wall portion is sequentially stretched to further increase the wall thickness. It becomes smaller and the hardness is increased by work hardening. After passing through the third ironing die 18D, the rectangular battery can 9 having a desired shape is completed. In this case, since the intermediate cup body 8 having a substantially elliptical shape having a small minor axis / major axis ratio, that is, an elliptical cross-sectional shape close to a rectangle is DI-processed, the DI battery is naturally processed by DI and the rectangular battery can 9 having a desired shape is formed. Can be manufactured stably.

Since the prismatic battery can 9 is removed from the drawing and ironing machine by the stripper 19, its upper side (ear) has a slightly distorted shape due to the above-mentioned processes. The ears are cut off to form the prismatic battery can 9 shown in FIG. On the bottom surface of the battery can 9, the uneven surface 8d formed during impact molding remains as it is.

In the method of manufacturing the prismatic battery can 9 of this embodiment, in the method of manufacturing the prismatic battery can of the above-mentioned prior application, the first step by deep drawing and the second step by redrawing at a plurality of stages are carried out.
The first step of producing the intermediate cup body 8 equivalent to the second intermediate cup body 3 produced by the above step in one step by impact molding, and the DI excellent in the production speed.
Since the rectangular battery can 9 having a desired shape can be manufactured by the second process by processing, the number of processes is greatly reduced as compared with the manufacturing method of the prior application, the productivity is remarkably improved, and an ellipse close to a rectangle is formed. Since the intermediate cup body 8 having a cross-sectional shape of the shape is subjected to DI processing, the rectangular battery can 9 having a desired shape can be easily manufactured, and at the same time, the DI processing is performed by one stroke of the DI punch 20 to perform meat processing. There is an advantage that dimensional accuracy such as thickness is improved.

FIG. 3 obtained by this embodiment.
The prismatic battery can 9 of (e) has an even wall thickness as a whole, but the impact molding of the first step of this embodiment is performed by forming the punch 13 and the hole wall of the processing hole 11 a of the die 11. Since it has a good shape selectivity that it can be easily formed into an arbitrary shape by setting the gap, the cross sectional shape like the rectangular battery can 4 of FIG. 5 (d) obtained by the manufacturing method of the prior application. Is substantially rectangular, and it is easy to form the short-side plate portion 4a in a shape having a larger thickness than the long-side plate portion 4b.

Further, according to this manufacturing method, the prismatic battery can 21 having the shape shown in the vertical sectional view of FIG. 3 (f) can be easily manufactured. This prismatic battery can 21 has a thin wall portion 21c having a wall thickness that is about 10% thinner than other portions around the openings in the short side plate portion 21a and the long side plate portion 21b, that is, around the sealing portion when the prismatic battery is formed. Are formed. The thin portion 21c can be formed by swelling a predetermined portion of the DI punch 13 of the drawing / ironing machine in the second step to a slightly larger diameter.

Next, a specific example of the method for manufacturing the prismatic battery cans 9 and 21 according to the above-described embodiment will be described.
First, the measured values when the first step was carried out are shown. The pellet 7 is an oval shape made of aluminum and has a thickness of 3.6 mm, a major axis of 30.9 mm, and a minor axis of 9.8 mm.
mm. The intermediate cup body 8 has a thickness of 0.4 mm, a major axis of 31.1 mm, and a minor axis of 10.0 mm. Subsequently, the prismatic battery can 9 shown in FIG. 3C manufactured through the second step has a short side plate 9a and a long side plate 9b each having a thickness of 0.2 mm or less and a bottom plate having a thickness of 0.4 mm. 29.5 mm long side, short side
It is 5.3 mm. By undergoing such shape conversion, the prismatic battery can 9 having high dimensional accuracy with almost no distorted deformation could be smoothly manufactured.

A specific example of a manufacturing method for manufacturing the same prismatic battery can in another pellet shape will be described. First, when the measured value when the first step was carried out is shown, the pellet is an oval shape having a rectangular cross section made of aluminum and having R at four corners, and its thickness is 3.6 mm. , Long side 29.5 mm, short side 5.0
mm. The intermediate cup has a thickness of 0.4 mm and a long side
30.0 mm, short side 5.5 mm.

Then, after the second step, the process shown in FIG.
A battery can similar to the prismatic battery can 9 shown in FIG. 2, the short side plate 9a and the long side plate 9b have a thickness of 0.2 mm, and the bottom plate has a thickness of 0.2 mm.
0.4 mm, the major axis was 29.5 mm, and the short side was 5 mm.
By undergoing such shape conversion, the prismatic battery can 9 having high dimensional accuracy with almost no distorted deformation could be smoothly manufactured. In particular, by making the cross-section into a substantially rectangular shape having R at the four corners of the rectangle, it is possible to suppress swelling of the bottom surface in the DI process, and the bending and drawing ratios are small, which facilitates the drawing process in the DI process. It has advantages such as

FIG. 4 shows the prismatic battery can 21 shown in FIG.
FIG. 3 is a vertical cross-sectional view showing a prismatic lithium-ion secondary battery configured using. In this prismatic battery, a sealing plate 22 is fitted to the inner peripheral edge of the opening of the prismatic battery can 21, and the prismatic battery can 21 and the mating part 23 of the sealing plate 22 are integrated by laser welding to be liquid-tight and air-tight. It is sealed by. Seal plate 22
Has a through hole 24 formed in the central portion of which is indented inward, and the through hole 24 is coated with a sealant composed of a mixture of blown asphalt and mineral oil. A synthetic resin gasket 27 which is liquid and electrically insulating is integrally attached.

A rivet 28 made of nickel or nickel-plated steel also serving as a negative electrode terminal is fixed to the gasket 27. This rivet 28 is a gasket 27
Is inserted into the central part of the base plate, and the front end part is fixed by caulking in a state where the washer 29 is fitted to the lower part of the base plate, and is fixed in a liquid-tight and air-tight manner to the gasket 27. Incidentally, the gasket 27 of this embodiment
Is integrally formed with the sealing plate 22 by injection molding. A substantially elliptical exhaust hole 30 is provided between the rivet 28 also serving as the negative electrode terminal and the outer edge of the sealing plate 22 on the long side.
The exhaust hole 30 is closed by an aluminum foil 31 which is pressure-bonded to and integrated with the inner surface of the sealing plate 22 to form an explosion-proof safety valve.

An electrode group 32 is accommodated in the accommodating portion of the power generating element of the prismatic battery can 21. This electrode group 32 is
Separator 33 made of microporous polyethylene film
Each of the positive electrode plate (not shown) and the negative electrode plate (not shown) is wound through the via, and the outermost periphery is wrapped with the separator 33 to form an oval cross section. The positive electrode lead 34 of the electrode group 32 is connected to the inner surface of the sealing plate 22 by spot welding with a laser beam, and the negative electrode lead plate 37.
Are connected to the washer 29 by resistance welding.

The sealing plate 22 is provided with a liquid injection hole 38, from which a predetermined amount of organic electrolyte is injected. After that, the liquid injection hole 38 is covered by fitting a lid plate 39, and the lid plate 39 and the sealing plate 22 are laser-welded to complete a prismatic battery. The electrode group 32 has been described as being wound in such a manner that its cross section has an oval shape. However, this prismatic battery can 21 has a plurality of separators 33 with a separator 33 interposed therebetween like a general prismatic cell. The present invention can also be applied to a case where a prismatic battery is formed by accommodating an electrode group formed by stacking a positive electrode plate and a negative electrode plate.

Since this prismatic battery is constructed by using the prismatic battery can 21 manufactured by the manufacturing method of the above-mentioned embodiment, the productivity is improved by the amount of manufacturing the prismatic battery can 21 with a small number of steps. Further, since the rectangular battery can 21 can be formed with a high dimensional accuracy in wall thickness and the like by the DI method, if the prismatic battery can 21 is formed as thin as possible, this prismatic battery can improve the volume energy density. It will have sufficient pressure resistance while working. Such an effect is shown in FIG.
Although the same can be obtained when the rectangular battery can 9 of (e) is used, when the rectangular battery can 21 is used, the fitting portion 23 between the sealing plate 22 and the rectangular battery can 21 is laser-welded. At this time, since the sealing plate 22 is supported by the step portion between the thin portion 21c of the prismatic battery can 21 and the other portion, there is no need for a means for supporting the sealing plate 22 and laser welding can be easily performed. There is.

Next, a method of manufacturing the prismatic battery can according to the second embodiment of the present invention will be described. In this manufacturing method, the intermediate cup body 8 similar to that of the first embodiment is molded by impact molding in the first step shown in FIG. 1, and this intermediate cup body 8 is shown in FIG. In the second step, DI processing is performed by a drawing and ironing machine. In FIG. 6, the same or equivalent parts as those in FIG. 2 are designated by the same reference numerals, and duplicated description will be omitted. This drawing / ironing machine differs from that shown in FIG. 2 only in the configuration of the DI punch 40. That is, the DI punch 40 is, as shown in the perspective view of FIG. 7A and the enlarged view of the portion A of FIG.
The rectangular cross-section corresponding to the prismatic battery can to be manufactured has a rectangular plate-like outer shape with a substantially rectangular cross-section, and grid-like processed grooves 41 are formed at positions from the lower ends to the predetermined positions on both long side surfaces thereof. . The lattice-shaped processed grooves 41 are communicated with each other through intersections 42 that intersect each other.

The DI process in the second step is basically the same as the second step in the first embodiment, but only the different points will be described. As shown in FIG. 8, the intermediate cup body 8 passes through the drawing die 18A and the first and second ironing dies 18B to 18C, and the cup body 36 that has been drawn and ironed is the third ironing die 1.
When passing 8D, this third ironing die 18
The inner surface of the can of the cup body 36 is strongly pressed against the outer surface of the DI punch 40 by the pressing force of the ironing hole having the smallest D. As a result, a part of the material on the inner surface side of the can of the cup body 36 is plastically deformed while the machining groove 4 of the DI punch 40 is formed.
1, the processed groove 41 is transferred to the inner surface of the can of the cup body 36, and the lattice-shaped convex bulging portion 43 corresponding to the processed groove 41 is formed.

When the protruding bulging portion 43 is formed on the inner surface of the can of the cup body 36, the material on the inner surface of the can of the cup body 36 is in a state in which resistance is added between the material and the DI punch 40. As a result, the material on the outer surface side of the can of the cup body 36 is mainly squeezed by the third squeezing die 18D without being processed, so that the third squeezing die 18D and the DI punch 40 are moved. It is possible to suppress the phenomenon of material surplus with 40 and smooth the material flow. Moreover, since the protruding bulging portion 43 is formed only on the long side plate portion of the cup body 36, the processing speed at the long side plate portion can be suppressed and the overall processing speed can be made constant. it can.

As a result, according to this manufacturing method, it is possible to manufacture a prismatic battery can having a uniform can thickness in which no wavy shape is formed on the inner surface and the outer surface of the can. In other words,
If DI processing is performed using a rectangular plate-shaped DI punch having a long side surface as a flat surface, the materials on the inner surface side and the outer surface side of the can of the cup body 36 are not processed along the DI punch and the ironing die. The phenomenon of material surplus occurs and DI
The waviness is caused by a partial thickness of the can that is smaller than the clearance between the punch and the ironing die. Also,
When processing a rectangular battery can with DI, the processing speed of the long side plate is faster than that of the short side plate, and the long side plate is stretched and thinned. By adopting the manufacturing method of this embodiment, it is possible to solve them all at once.

FIG. 9 is a perspective view showing a vertical cross-sectional shape of a prismatic battery can 44 obtained by the manufacturing method of the second embodiment, and FIG. 9 (b) is an enlarged view of a part of the battery can 44. The shown perspective view and (c) are some enlarged sectional views. This prismatic battery can 44 has a bottomed rectangular tubular outer shape with a rectangular transverse cross section, and has a DI on the inner surface of the long side plate portion 44a.
A large number of convex bulging portions 43 having a lattice shape similar to the lattice shape of the processing grooves 41 of the punch 40 are formed, and these convex bulging portions 43 are connected to each other via intersection points 47. There is.

The prismatic battery can 44 has a thickness that is as thin as possible, but the grid-shaped convex bulging portion 43 has a strength that can function as a reinforcing bar and effectively suppress bulging deformation. In addition, it has extremely high pressure resistance, and the outer surface and the inner surface of the can are both highly precise flat surfaces without waviness. Further, in this prismatic battery can 44, since the ridge bulging portions 43 are connected to each other through the intersections 47, the direction in which the ridge bulging portion 43 increases the strength is 2 directions.
More than the direction, the pressure resistance is higher.

More specifically, referring to FIG. 9C, the convex bulging portion 43 has the bulging height H, width W and interval K set to values within the following ranges. If formed on the inner surface of the battery can, it is possible to obtain the required effect of effectively suppressing bulging and deformation in response to an increase in battery internal pressure while ensuring a sufficient energy density.

That is, the bulging height H of the convex bulging portion 43
Is the thickness of the battery can (for rectangular battery cans, the long side plate 44a
It is preferable to set it in the range of 5 to 50% of the can thickness D). If it is less than 5%, the effect of suppressing the bulging deformation is small, and if it is 50% or more, not only the volume of the battery can decreases and the volume energy density is lowered, but also the manufacturing of the battery can itself becomes difficult. A more preferable bulge height H is set to a value within the range of 5 to 20% of the can thickness D, and the most preferable bulge height H is within the range of 5 to 10% of the can thickness D. It is to set, and the concrete numerical value is 0.01 mm ~
It is 0.02 mm.

The width W of the convex bulging portion 43 is preferably set within the range of 1 to 30 times the bulging height H. If it is 1 time or less, it is not possible to form the ridge bulging portion 43 having the bulge height H that can effectively suppress the bulging deformation, and if it is 30 times or more, the internal volume of the battery can becomes small and the volume energy density Cause decline. A more preferable width W is set to a value within a range of 5 to 20 times the bulging height H, and a most preferable width W is set to a value within a range of 10 to 15 times the bulging height H. is there.

Furthermore, it is preferable that the interval K between the convex bulging portions 43 is set within the range of 2 to 20 times the width W.
If it is 2 times or less, the inner volume of the battery can becomes small and the volume energy density is lowered, and if it is 20 times or more, the effect of suppressing bulging deformation becomes insufficient. More preferable interval K is width W
It is to be set within the range of 5 to 15 times.

Further, FIG. 10A is a view seen from the opening of the intermediate cup body 8 manufactured through the first step in the manufacturing method of the second embodiment, and FIG. It is the figure seen from the opening part of the prismatic battery can 44 manufactured by going through a process. Intermediate cup-shaped 8 (a), the thickness T ₁ of the long side side plate portions 8a, the thickness T ₂ of the short side plate portion 8b, the thickness T ₃ of the corner portion 8c, T ₁ <relative relationship of T ₂ <T ₃ It has the shape Specifically, the thickness T ₁ of the long side plate 8a is 0.40 mm, the thickness T ₂ of the short side plate 8b is 0.55 mm, and the thickness T ₃ of the corner 8c is 0.75 m.
m. The bottom plate has a thickness of 0.40 mm.
The first impact molding is performed by the punch 13 as described above.
Since it has a good shape selectivity that can be easily formed into an arbitrary shape by setting a gap between the hole wall of the machined hole 11a of the die 11 and the hole wall of the die 11, the thicknesses T _{1 to} T _{3 of the} respective parts described above have different shapes. The intermediate cup body 8 can be manufactured easily and quickly in one step.

The intermediate cup body 8 having the above-described shape has the long side plate portion 8 excluding the bottom plate portion when DI processing is performed in the next step.
Since the a, the short side plate portion 8b and the corner portion 8c are squeezed at substantially the same ratio, it is possible to surely obtain the battery can 44 having a desired can thickness while surely preventing the occurrence of defects such as tearing and tearing. be able to.

The prismatic battery can 44 shown in (b) has a long side plate 4
Cans thickness t ₁ of 4a, the can thickness t ₂ of the short side plate portions 44b, cans thickness t ₃ of the corner portion 44c, like the intermediate cup-shaped 8, the shape of the relative relationship of t ₁ <t ₂ <t ₃ keeping. Specifically, the can thickness t ₁ of the long side plate portion 44a is 0.
20 mm, can thickness t ₂ of the short side plate portion 44b is 0.30 m
m, the can thickness t ₃ of the corner portion 44c is 0.50 mm. This is a result of molding the entire peripheral side surface of the intermediate cup body 8 to be substantially evenly thin by DI processing. The thickness of the bottom plate is 0.4, which is the same as that of the intermediate cup body 8.
It remains 0 mm.

Therefore, the thickness T having a ratio corresponding to the ratio of the can thicknesses t _{1 to} t ₃ of the respective parts of the rectangular battery can 44 having a desired shape.
_{If the} intermediate cup body 8 having _{1 to} T ₃ is manufactured in advance by impact molding, the DI process facilitates the control for obtaining the rectangular battery can 44 having the required can thickness t _{1 to} t ₃ , and The processing load is reduced. Further, the bottom plate portion is formed into a predetermined can thickness at the time of impact molding in the first step, and the can thickness does not change even after DI processing, so that the predetermined can can be surely formed in as few steps as possible. It can be formed to a thickness.

In the battery can 44 having the above-described shape, when the internal pressure of the battery rises, the force to bulge and deform the long side plate portion 44a outward and the short side plate portion 44b to inwardly dent. Since the force acts at the same time, the short side plate portion 44b having a can thickness t ₂ larger than that of the long side plate portion 44a effectively prevents outward expansion of the long side plate portion 44a. Further, since the long side plate portion 44a tries to bulge outward and deform while using the corner portion 44c as a fulcrum, the short side plate portion 4a.
Corner part 4 in which the can thickness t ₃ is made larger than that of 4b
4c effectively prevents outward expansion of the long-side plate portion 44a.

Therefore, the long side plate portion 44a effectively prevents the long side plate portion 44a from outwardly bulging and deforming as the internal pressure of the battery rises, even though the can thickness t ₁ is set to the minimum value. The can thickness t of the long side plate portion 44a which can secure the strength and has the largest surface area in the peripheral wall portion.
By minimizing ₁ , the volume for accommodating the power generation element can be increased. In addition, the can thickness t of the corner portion 44c
₃ does not cause a reduction in the capacity of the electrode group even if the wall thickness is formed by bulging inward by the amount of the void generated between the electrode group housed in the battery can 44.

The long side plate 4 of the prismatic battery can 44 is also used.
The can thickness t _{1 of} 4a can be made as thin as possible at 0,20 mm as described above. Because the long side plate 44a is
Since the bulging deformation is effectively suppressed by the grid-shaped convex bulging portion 43, it is possible to form the can thickness t ₁ as small as possible of 0.25 mm or less. In other words, this prismatic battery can 44 has a can thickness t ₁ of the long side plate portion 44a of 0.
The problem that the bulging deformation is likely to occur when the thickness is reduced to 25 mm or less is solved by forming the lattice-shaped convex ridge bulging portion 43.

FIGS. 11A and 11B are schematic perspective views showing the manufacturing process of the method for manufacturing a prismatic battery can according to the third embodiment of the present invention in the order of steps. In this manufacturing method, through the steps similar to the first step and the second step in the first embodiment, as shown in FIG. 3E, the rectangular battery can 9 of the first embodiment is obtained. A corresponding battery can body 48 is manufactured.

Then, as shown in FIG. 11A, a processing core 49 is press-fitted into the battery can body 48. The processing core 49 is a rectangular plate material having a substantially rectangular cross-sectional shape that can be fitted in the battery can body 48, and has grid-shaped processing grooves 50 on the long side surfaces on both sides thereof. Has been formed. That is, the processing core 49 has substantially the same shape as the DI punch 40 used in the second step of the second embodiment.

As shown in FIG. 11 (b), a pair of pressure rollers 51 are pressed against the outer surface of the open ends of the long side plate portions on both sides of the battery can body 48 having the processing core 49 fitted therein. It is pressed in the state of adding. And the battery can body 48
Is moved so as to pass through between the pair of pressing rollers 51 which are pressed from both sides, as indicated by the arrow in (b). At this time, the both long side plates of the battery can body 48 are strongly pressed against the processing core 49 by the pressure applied by the pressing roller 51, so that part of the material on the can inner surface is plastically deformed. Meanwhile, the machining groove 50 of the machining core 49 enters into the machining groove 50 and the machining groove 50 is transferred to the inner surface of the can, and the same battery can as shown in the second embodiment is completed. Therefore, according to this manufacturing method, the prismatic battery can similar to that of the second embodiment can be manufactured with high accuracy by a smooth material flow.

[0084]

As described above, according to the method for manufacturing a prismatic battery can of the present invention, an intermediate cup body having a substantially elliptical cross section can be manufactured all at once by impact molding which can be manufactured in an arbitrary shape in one step. Since this intermediate cup body is made into a prismatic battery can by the DI method, both have only the first and second steps of forming only by one stroke movement of the punch, and the number of steps is remarkably small. And productivity is significantly improved. Further, since the intermediate cup body is processed by DI, a rectangular battery can having a desired shape can be easily and surely manufactured, and dimensional accuracy such as wall thickness is improved, so that the wall thickness can be made as thin as possible. It is possible to manufacture a prismatic battery can having excellent pressure resistance.

As described above, according to the prismatic battery can of the present invention, when the internal pressure of the battery rises, the short side plate having a can thickness larger than that of the long side plate bulges outward toward the long side plate. Effectively prevent. Also, since the long side plate part tries to deform outward with the corner part as a fulcrum, the corner part with a larger can thickness than the short side plate part is effective for outward bulging deformation of the long side plate part. To prevent it. Therefore, while the long side plate portion is set to have the smallest can thickness, it is effectively prevented from expanding and deforming outward as the battery internal pressure rises, and sufficient pressure resistance can be secured. The volume of the power generating element can be increased by minimizing the can thickness of the long side plate having the largest surface area in the peripheral wall portion.

Further, according to the prismatic battery of the present invention, the productivity can be improved by manufacturing the prismatic battery can with a small number of steps, and the wall thickness of the prismatic battery can can be formed with high dimensional accuracy. By forming as thin as possible, it is possible to obtain sufficient pressure resistance while improving the volume energy density.

[Brief description of drawings]

1A to 1C are schematic vertical cross-sectional views showing a first step of a method for manufacturing a prismatic battery can according to a first embodiment of the present invention in the order of steps.

FIG. 2 is a schematic vertical sectional view of a second step in the same embodiment.

3 (a) and 3 (c) are perspective views showing pellets which are the battery can material in the above embodiment, and FIGS. 3 (b) and 3 (d) are perspective views showing the intermediate cup body manufactured in the first step. Figure,
(E) is a partially broken perspective view showing a prismatic battery can manufactured through the second step, and (f) is a longitudinal sectional view showing another prismatic battery can manufactured through the second step.

FIG. 4 is a vertical sectional view showing a prismatic battery configured using the prismatic battery can of FIG. 3 (c).

5A is a plan view showing a battery can material in a conventional method for manufacturing a prismatic battery can, FIG. 5B is a perspective view showing a first intermediate cup body manufactured in the first step, and FIG. ) Is a perspective view showing a second intermediate cup body manufactured in the second step,
(D) The partially broken perspective view which shows the prismatic battery can manufactured through the 3rd process.

FIG. 6 is a schematic transverse sectional view of a second step in the method for manufacturing a prismatic battery can according to the second embodiment of the present invention.

7A is a perspective view showing a DI punch used in a second step in the above manufacturing method, and FIG. 7B is an enlarged view of a portion A of FIG. 7A.

FIG. 8 is a partial cross-sectional view showing a can-making process in a second step of the above manufacturing method.

9A is a perspective view showing a vertical cross-sectional shape of a prismatic battery can manufactured by the above manufacturing method, and FIG. 9B is an enlarged perspective view of a part of the inner surface of the battery can. , (C)
Is an enlarged sectional view of a part of the battery can.

FIG. 10 (a) is a view seen from the opening of the intermediate cup body manufactured by the first step in the above manufacturing method,
(B) is the top view seen from the opening part of the prismatic battery can manufactured through the 2nd process.

11 (a) and 11 (b) are schematic perspective views showing the manufacturing process of the method for manufacturing the prismatic battery can according to the third embodiment of the present invention in process order.

[Explanation of symbols]

7 Pellet 8 Intermediate Cup Body 9, 21, 44, 48 Rectangular Battery Can 22 Sealing Plate (Sealing Body) 32 Electrode Group (Power Generation Element) 40 DI Punch 41 Machining Groove 43 Convex Lines 44a Long Side Plate 44b Short Side side plate portion 44c corners 47 intersection 48 cell Kanmototai 49 working core t ₁ long side plate of the can thickness t ₂ cans thickness of the can thickness t ₃ corners of the short side plate portion

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuhiko Mori             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Shoji Yamashita             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Kazuyuki Higashi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Tadahiro Tokumoto             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Masatoshi Hano             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5H011 AA09 BB04 CC06 DD01 DD03                       DD05 DD06 KK01 KK02                 5H029 AJ14 BJ02 CJ02 CJ03 CJ06                       DJ02 EJ01 HJ04

Claims (14)

[Claims] 1. A first step of impact-molding pellets of a predetermined shape to form an intermediate cup body, and the intermediate cup body being subjected to DI processing for continuously performing drawing and ironing at once. And a second step of forming a prismatic battery can having a substantially rectangular cross section. 2. A first step of impact-molding pellets having a predetermined shape to form an intermediate cup body, and the intermediate cup body having at least a long side surface of a rectangular plate material having a rectangular cross-sectional shape. Using a DI punch formed in a lattice shape to perform DI processing in which drawing and ironing are continuously performed at once, the cross section is a rectangular shape having a substantially rectangular shape, and at least the long side plate portion thereof is formed. A second step of forming a prismatic battery can in which a plurality of ridge-shaped bulging portions that bulge and extend linearly on the inner surface of the can in a thickness direction are arranged in a grid pattern. A method for manufacturing a prismatic battery can, characterized in that 3. DI machining is performed using a DI punch engraved in a state where a plurality of machining grooves forming a lattice are communicated with each other through intersections intersecting each other, and the DI machining is performed mutually through each intersection. The method for manufacturing a prismatic battery can according to claim 2, wherein a plurality of convex bulging portions forming a connected grid shape are formed on the inner surface of the can. 4. A first step of impact-molding pellets of a predetermined shape to form an intermediate cup body, and a DI process of continuously performing the drawing process and the ironing process on the intermediate cup body at one time. The second step of forming a prismatic battery can body having a substantially rectangular cross-section, and a process in which machining grooves are formed in a grid pattern on at least the long side plate portion of the square plate material in the battery can body. Third press-fitting core
And the step of pressing the pressing member onto the entire outer surface of the long side plate portions on both sides of the battery can body while plastically deforming a part of the material on the can inner surface of the battery can body. A fourth step of causing the lattice-shaped convex bulge portions corresponding to the processed grooves to be transferred and formed on the inner surface of the can by being inserted into the processed grooves. Production method. 5. A battery can material or pellets of the battery can material formed into a predetermined shape are annealed,
The pellets are subjected to impact molding.
5. The method for manufacturing a prismatic battery can according to any one of to 4. 6. The method for manufacturing a prismatic battery can according to claim 1, wherein the intermediate cup body obtained by impact molding is annealed and then the intermediate cup body is subjected to DI processing. . 7. A ratio of the thickness of the long side plate / the thickness of the bottom plate is 0.6 to 6 by impact molding the pellets.
1.3, the ratio of the thickness of the short side plate / the thickness of the bottom plate is 1.
The method for manufacturing a prismatic battery can according to claim 1, wherein an intermediate cup body having a shape of 0 to 1.8 is formed. 8. The pellet is impact-molded so that it has a rectangular cross-section with a substantially rectangular cross section, and the long side plate portion, the short side plate portion, and the corner portion have a large plate thickness in this order. The method for manufacturing a prismatic battery can according to claim 1, wherein an intermediate cup body having such a shape is formed. 9. The method for manufacturing a prismatic battery can according to claim 1, wherein the pellets are made of aluminum or an aluminum alloy. 10. The prismatic battery can according to claim 1, wherein the pellet is formed into an oval shape or a substantially rectangular shape having a plan view shape corresponding to the outer shape of the cross-sectional shape of the prismatic battery can to be manufactured. Manufacturing method. 11. A manufacturing method according to any one of claims 1 to 10, which is a bottomed rectangular tube having a substantially rectangular cross section, and has long side plate portions, short side plate portions and A prismatic battery can having a shape in which the thickness of each can increases in the order of the corners. 12. The can according to claim 1, wherein the long side plate has a can thickness of 0.25.
A prismatic battery can having a shape of not more than mm. 13. A prismatic battery can manufactured by the manufacturing method according to claim 1, wherein a power generating element is housed inside the prismatic battery can, and an opening is sealed with a liquid. A prismatic battery that is tightly sealed. 14. The method for manufacturing a prismatic battery can according to claim 1, wherein the intermediate cup body is molded by impact molding of a pellet using a punch having an uneven surface.