JPH0855613A - Manufacture of battery can - Google Patents

Abstract

PURPOSE:To fill many power generating elements into an iron battery can so as to efficiently manufacture the can by decreasing the thickness of the can at its side portion over at its bottom one and at the same time decreasing the thickness of nickel plating given to the can at its side portion over at its bottom one. CONSTITUTION:An iron battery can 3 is manufactured by preparing a nickel-plated iron shallow cup material 3' of diameter larger than the desired outside diameter of the can 3, feeding the material 3' to plural drawing dies 13a, 13b and up to 13n arranged in a multistage fashion on a coaxial line in such order that their contracting and drawing diameters can be gradually decreased and pressurizing on a punch 14 the material 3' into being connectively passed through the final-stage die 13n having its contracting and drawing diameter predesigned to correspond with the desired outside diameter of the can 3. Also because iron as the material 3' is beforehand plated with nickel, the extension of the nickel plating can follow that of the iron followed by the contracting and drawing of the material 3', and the nickel-plated iron battery-can 3 can consequently be manufactured in no such condition that pressure and generated heat are exerted on the material 3' to peel the nickel plating off the material 3' and to rough the nickel plating. The thickness of the can 3 can thus be more decreased at its cylindrical portion than at its bottom one to increase the contents of the can 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a can in a battery using an iron can as a terminal and container for accommodating a power generating element such as an alkaline manganese battery, a nickel-cadmium battery, and a lithium battery.

[0002]

2. Description of the Related Art In a normal manganese dry battery, a zinc can is used as a negative electrode active material / terminal container containing an anode mixture, a separator and the like. The zinc can here can be easily manufactured by impact forming a billet piece (disc-like piece) due to the ease of processing of the material, and the thickness of the cylinder side is smaller than the thickness of the bottom of the can. It was possible to make it thinner.

On the other hand, in the alkaline manganese battery, the positive electrode,
Iron cans are usually used as terminals and containers for the power generation elements such as the negative electrode and electrolyte. In the case of an iron can, it is not necessary to increase the thickness of the cylindrical side portion rather than the pressure of the positive electrode mixture and the internal pressure resistance, and it is necessary to increase the thickness of the can bottom portion. However, in general, the method of manufacturing iron cans has been so-called transfer squeezing, in which the cans are transferred to a plurality of dies having different squeezing diameters.

[0004] Iron can 1 obtained by this transfer drawing
In FIG. 9, the thickness of the can bottom 1a is smaller than the thickness of the side 1b near the can bottom as shown in an enlarged cross section in FIG. For example, in a can of a C type battery, the thickness of the bottom part is 0.1.
295 mm, the thickness of the side near the bottom is 0.325 mm
Met. Therefore, in order to maintain the required thickness of the bottom portion 1a, it is necessary to use a can having an excessively large thickness of the side portion 1b.

[0005] This leads to a problem that the substantial inner diameter and the internal volume of the iron can are reduced and the weight of the can is increased, thereby lowering the battery capacity and the weight efficiency. In addition, the inner and outer surfaces of the iron can 1 due to transfer drawing are smooth with a surface roughness of about 2 to 5 μm, and the contact area cannot be sufficiently reduced due to a small substantial contact area with the positive electrode mixture. This was a cause of performance degradation. By the way, the battery was assembled using the above-mentioned C-size battery can, and the electrical characteristics after storage at 60 ° C. for one month were examined for 50 samples. The following results were obtained. Note that the 1Ω continuous discharge characteristic is represented by an average value with 0.9 V as a final voltage.

Surface roughness of inner surface of can 2-5 μm Open circuit voltage 1.569-1.571 V Internal resistance 0.100-0.122 Ω Short-circuit current 6.0-8.1 A 1 Ω Continuous discharge time 104 minutes 6.85 To prevent rust and reduce the contact resistance with the positive electrode mixture, nickel plating should be applied to the inner surface of the can. However, nickel plating after forming into the can is due to insufficient flow of the plating solution. Sufficient plating cannot be obtained. Incidentally, the plating thickness at the center of the outer side wall of the can was 2.5 to 3.0 μm, the plating thickness at the center of the inner side wall was 0.05 to 0.10 μm, and that at the bottom was almost the same as that of the inner side wall. . In addition, when a transfer drawing process is performed on a can made of an iron material that has been plated in advance, there is a problem that the plating is peeled or roughened as the process is performed.

There are some prior arts that can be used as a reference for solving such a problem. For example, JP-A-55-80.
Japanese Patent Publication No. 265/265 discloses a configuration in which the side portion is made thinner than the bottom of an iron can, and Japanese Patent Application Laid-Open No. 55-131959 discloses a technique in which the plating thickness of the can varies depending on the location. However, in order to improve the battery capacity and weight efficiency aimed at by the present invention, for a battery configured to make the thickness of the can bottom part and the can side part different for both the iron can and the nickel plating applied thereto. There is no idea of a can.

[0008] Further, although not in the field of batteries, a method of manufacturing a can is disclosed in Japanese Patent Publication No. 54-39234, which discloses a technique of cold ironing a cylindrical body. A method of drawing while sequentially reducing the diameter (Japanese Patent Publication No. 41-3366) or a method of sequentially arranging multi-stage dies on one axis and performing drawing in one operation stroke of the punch (Japanese Patent Publication No. Sho 41). However, none of these methods draws and irons a surface-treated material, that is, a nickel-plated iron plate.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, and secures the strength of a can, etc. in a necessary portion, and at the same time, the inner diameter and the inner volume of the iron can are large.
An object of the present invention is to provide a preferable method for manufacturing a battery can that can accommodate a large amount of power generation elements and is excellent in battery capacity and weight efficiency.

[0010]

The present invention is applied to an iron material by sequentially forming an iron can from an iron material by drawing and ironing a can side portion of a nickel-plated iron can. The nickel-plated part is made to follow the elongation of the iron material so that it can be stretched, thereby manufacturing a battery can in which both the iron can part and the nickel-plated part have a can side thickness that is smaller than the can bottom thickness. can do.

Further, as a manufacturing method capable of mass production, nickel-plated iron materials are arranged so as to be successively drawn so that the ironing diameter becomes smaller, and the ironing diameter of the final-stage ironing die is set to a desired can outer diameter. BACKGROUND ART A battery can is manufactured by pressing a plurality of ironing dies arranged in multiple stages with a punch, continuously passing the ironing dies, and squeezing and ironing.

[0012]

[Function] By ironing the can side of a nickel-plated iron can, the nickel-plated portion applied to the iron material is stretched to follow the elongation of the iron material. Both of the parts can be made thinner than the bottom of the can, and a good battery can can be efficiently obtained without peeling of plating or roughening.

Hereinafter, the present invention will be described in detail with reference to examples.

[0014]

EXAMPLE FIG. 1 shows a unit cell whose left half is a cross section of a cylindrical alkaline manganese battery in an example of the present invention.

In the figure, reference numeral 3 denotes an iron can serving as both a positive electrode terminal and a container, and the thickness of the cylindrical side portion 3b is formed smaller than the thickness of the bottom portion 3a. Reference numeral 4 is a positive electrode mixture which is pressurized and installed in the iron can 3 in a cylindrical shape, 5 is a bottomed tubular separator, 6 is a gelled zinc negative electrode, and 7 is a negative electrode current collector. Is located inside the negative electrode 6 by penetrating the central portion of the synthetic resin sealing body 8, and the nail-shaped top portion is spot-welded to the negative electrode terminal plate 9 arranged outside the sealing body 8. FIG. 2 is a half cross-sectional view of a cylindrical alkaline manganese battery completed by disposing the positive electrode terminal plate 10 on the bottom of the unit cell and covering the outer periphery with a heat-shrinkable resin tube 11 and a metal outer can 12. is there. When the cylindrical alkaline manganese battery of this embodiment is a single C type, the thickness 3a at the bottom of the can 3 needs to be about 0.3 mm, but the thickness at the side of the cylinder is 0.3 mm because of its high rigidity. In this case, the bottom thickness was 0.5 mm and the side thickness was 0.25 mm. FIG. 3 is a sectional view showing only the iron can 3. The can outer diameter φ is 24.6 mm and the height h is 41.4.
mm, the inner volume can be increased by 1.7% as compared with the conventional can with both bottom thickness and side thickness of 0.3 mm.

According to the study of the present inventors, the relationship between the thickness 3a of the bottom of the iron can and the thickness 3b of the side of the cylinder depends on the size of the can. 0.7mm, 3b is 0.
A range of 1 to 0.3 mm is preferred. By the way, the tensile strength of the can of this size is 60kg for the conventional transfer drawn can.
/ Mm ² and that of the can of this example was 85 kg / mm ² . Further, the load causing cracking in the can-expanding test was 240 kg on average in the conventional can, whereas it was 408 kg in the present example.

Further, the inner surface of the can 3 penetrates into the positive electrode mixture 4 which is formed under pressure, so as to increase the contact area with the mixture.
It is advisable to form a large number of thin vertical stripes 3c for roughening as shown in FIG. At this time, it is preferable that the edge portion 3d of the inner surface of the can be a mirror-like smooth surface in order to improve the close contact with the sealing body 8 and the liquid-tightness and airtightness.

The iron can 3 is manufactured by the method shown in FIGS. 5A and 5B. That is, a nickel-plated iron cup material 3 ′ having a diameter larger than the desired outer diameter of the can and shallow.
And squeeze them in order to reduce the iron diameter,
Multiple ironing dies 13 arranged in multiple stages on the coaxial line
a, 13b, 13c, 13n, and is obtained by continuously pressurizing with a punch 14 to a die having the desired outer diameter of the drawing and ironing in the final stage 13n.

If a small radius 14a is applied to the corner of the tip of the punch 14, the iron can 3 can be continuously drawn and pressed by a small amount, as shown in FIG. It does not cause extreme necking.

The inner and outer surfaces of the can 3 are usually finished to be smooth by applying the continuous drawing and ironing pressure, which is effective in eliminating the adhesion of dust and foreign matter. In particular, since the material iron is pre-plated with nickel, the nickel plating can follow the elongation of iron caused by drawing and ironing,
A nickel-plated iron can can be obtained in a state where peeling and roughness do not occur due to pressure and heat generation.

In this case, the plating thickness of the central portion of the outer side wall of the can is 1.4 to 1.7 μm, and that of the central portion of the inner side wall is 1.5 to 1.5 μm.
The thickness was 1.7 μm, and that of the inner bottom was 2.5 to 2.9 μm, which was thick and uniform. Therefore, it is effective in preventing rust and reducing the contact resistance with the positive electrode mixture.

As shown in FIG. 7, by tapering the peripheral surface of the tip of the punch, the bottom thickness 3a and the side thickness 3b are connected smoothly depending on the taper shape. The connecting portion 3f can be provided to enhance the corner strength or obtain a free corner shape.

Further, even if a large pressure is applied during the re-molding of the anode mixture in the can, the connecting portion 3f is not constricted in terms of thickness, so that there is no buckling deformation. Therefore, the manufacturing of batteries can be prevented.

As described above, it is preferable to form fine vertical stripes 3c on the inner surface of the can to improve the adhesion between the positive electrode mixture 4 and the inner surface of the iron can 3 and reduce the contact resistance. In processing, a thin vertical streak is formed on the peripheral surface of the tip portion of the punch 14 in parallel with the axis of the punch, and the inner surface of the can is strongly pressed against the peripheral surface of the punch by the pressing force from the die when the ironing die is passed. Can be easily formed by transferring.
It is difficult to transfer a vertical streak on the peripheral surface of the punch by simple drawing.

FIG. 8 shows a partially enlarged cross section of the iron can 3 whose inner surface is roughened by the vertical bar 3c. The vertical bar 3c has a protrusion height 15 of 0.002 in the case of a single 2 type alkaline manganese battery.
5 to 0.02 mm, pitch 16 between muscles is 0.002 to 0.4 m
A range of m is preferred. Within this range, the nickel plating applied will also elongate following the elongation received during drawing and ironing of the can, and plating will be secured in a state that covers the streaks formed by the combination of pressure and heat generation during processing Is done. If the height of the vertical streaks is low, contact with the positive electrode mixture cannot be expected sufficiently.On the contrary, if the height is too high, separation from the punch becomes difficult, and the life of the punch is shortened. It should be kept in an appropriate range. Also, the pitch between the stripes should be set within the above range in consideration of separation from the punch.

By the way, a battery was assembled using such a C-size battery can, and the electrical characteristics after storage at 60 ° C. for one month as described above were examined for 50 samples. The battery characteristics were superior to those of the conventional can having a smooth surface. The 1Ω continuous discharge characteristics are shown as average values.

Surface roughness of inner surface of can 9-11 μm Open circuit voltage 1.569-1.571 V Inner resistance 0.075-0.090 Ω Short-circuit current 7.7-9.0 A 1Ω Continuous discharge time 114 minutes Same standard deviation 4.67

[0028]

As described above, according to the present invention, the thickness of the side portion is made smaller than the thickness of the bottom portion of the battery can, and at the same time, the iron can and the nickel plating applied thereto are By making both sides thinner than the bottom thickness, both can strengths and electrical resistances can be reduced at the bottom of the can.
In addition, as a whole, a large amount of power generating elements can be included, and the battery capacity and weight efficiency which have not been achieved can be improved.

In particular, in the case of a battery in which the nickel-plated portion at the bottom of the battery can is directly exposed to the outside, it is necessary to ensure abrasion resistance, and the plating thickness at the side is reduced while maintaining the plating thickness at the bottom of the can. The effect that can be done is great.

Further, in this manufacturing method, iron cans are sequentially formed from the iron material by drawing, and the can side portion of the nickel-plated iron can is ironed to obtain nickel plating on the iron material. The part is stretched by following the elongation of the iron material, which makes it possible to make both the iron can part and the nickel-plated part the thickness of the can side part thinner than the thickness of the bottom part of the can, and also to prevent the plating from peeling or roughening. Therefore, it is possible to efficiently obtain a good battery can.

Further, the battery cans are sequentially drawn and arranged so that the ironing diameter becomes smaller, and the ironing diameter of the ironing die of the last stage is set to a desired outer diameter of the can. If it is formed by pressing and continuously passing and drawing and ironing, it can be manufactured more efficiently and can exhibit a remarkable effect corresponding to mass production.

[Brief description of drawings]

FIG. 1 is a side view of a left half of an alkaline manganese battery in a cross section according to an embodiment of the present invention.

FIG. 2 is a half cross-sectional view of the battery completed by applying an outer package.

FIG. 3 is a cross-sectional view of an iron can using the manufacturing method of the present invention.

FIG. 4 is a perspective view showing a vertical streak formed on the inner surface of the iron can.

FIG. 5 is an explanatory view of the production method of the present invention in which a desired iron can is squeezed and ironed from A and B cup materials.

FIG. 6 is an enlarged cross-sectional view of a main part of a battery can which is manufactured by the manufacturing method of the present invention.

FIG. 7 is an enlarged sectional view of a main part of the battery can in another example.

FIG. 8 is an enlarged sectional view showing a vertical streak portion formed on the inner surface of the can.

FIG. 9 is a partially enlarged cross-sectional view showing a main part of a conventional battery iron can.

[Explanation of symbols]

 3 Iron can 3'Cup material 3a Bottom part 3b Cylindrical side part 3c Rough surface (vertical streak) 3f Connecting part connecting the bottom part and side parts 13a, 13b, 13c, 13n Ironing die 14 Punch 14a R

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshimichi Ishii 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Satoshi Nishikawa 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Osamu Ikeda 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A nickel-plated iron material is drawn into a bottomed tubular shape, and the side portion of the bottomed tubular iron can is subjected to ironing so that the thickness of the bottom of the can is smaller than that of the can. The thickness of the part is made thin, and the nickel-plated portion applied to the iron material is extended by following the elongation of the iron material, and the side portion of the can is covered by the thickness of the nickel-plated portion that covers the bottom portion of the can. A method for manufacturing a battery can, wherein the nickel-plated portion is formed thin. 2. An iron material which is nickel-plated and preformed in a cup shape having a diameter larger than a desired outer diameter of the can is used. Non-ironing dies The ironing diameter of the can is determined by pressing the ironing diameter of the cans into a plurality of multi-tiered ironing dies with the desired ironing diameter. The nickel-plated portion of the iron material is made to follow the elongation of the iron material, and the nickel-coated portion that covers the bottom of the can is covered by the nickel-coated portion that covers the bottom of the can. A method for manufacturing a battery can, which is characterized in that the plated portion is formed thin. 3. The battery can according to claim 2, wherein a rounded portion that connects the inner surface of the bottom of the can and the inner surface of the side of the can is formed in the can by using a punch having a rounded corner. Manufacturing method. 4. A can is formed with a connecting portion for smoothly connecting the difference between the thickness of the bottom of the can and the thickness of the side of the can by using a punch having a taper on the tip peripheral surface. 2. The method for producing a battery can described in 2. 5. The manufacturing of a battery can according to claim 2, wherein a plurality of vertical stripes are formed on the inner surface of the can by using a punch having a vertical stripe parallel to the axis of the punch on the peripheral surface. Law. 6. The method of manufacturing a battery can according to claim 5, wherein a vertical streak of the punch is formed so that the vertical streak does not enter at the rim portion of the inner surface of the can.