JP2007066762A - Battery can and alkaline dry cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery can which ensures a good contact status with a cathode mixture. <P>SOLUTION: The cylindrical battery can with a bottom is provided with: a cylindrical side part consisting of a thin-walled part formed on a bottom part side; and a thick-walled part thicker than the thin-walled part formed on an opening part side. The thick-walled part is made thicker towards inside of the cylindrical side part, an outer diameter of the cylindrical side part has the same size from the opening part to the bottom part, and the thin-walled part is an oval shape with a roundness from 0.1 to 1.0 mm on a surface perpendicular to an axis direction of the cylindrical side part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery can, particularly a battery can for an alkaline dry battery.

  Conventionally, various studies have been made on battery cans of alkaline dry batteries. For example, in Patent Document 1, the thickness of the body portion that stores the positive electrode mixture in the cylindrical side portion of the bottomed cylindrical battery can is made thinner than 0.18 mm, and the thickness of the opening end portion in the cylindrical side portion is reduced. It has been proposed to make the opening end thicker toward the inside of the cylindrical side portion so that the thickness is 1.4 times or more the thickness of the body portion. Thereby, the internal volume of a battery can can be increased, ensuring the intensity | strength of the opening edge part of a battery can.

By the way, in an alkaline battery, a bottomed cylindrical battery can also serves as a positive electrode terminal, and a hollow cylindrical positive electrode mixture is in contact with the inside of the battery can.
However, as described above, the opening end in the cylindrical side portion of the battery can is thicker toward the inside of the cylindrical side portion than the body portion, and the positive electrode mixture is smaller than the inner diameter of the body portion. Since it is inserted from the opening, there is a problem that the clearance between the positive electrode mixture and the battery can is increased, the contact state between the two is deteriorated, the internal resistance of the battery is increased, and the heavy load discharge performance is liable to be lowered. .
JP 2002-151017 A

  Therefore, an object of the present invention is to provide a battery can capable of ensuring a good contact state with a positive electrode mixture in order to solve the above-described conventional problems.

  The battery can of the present invention is a bottomed cylindrical battery can having a cylindrical side portion, a bottom portion, and an opening portion, and the cylindrical side portion includes a thin portion formed on the bottom portion side and the opening portion. The thick part is thicker than the thin part formed on the side, and the thick part is thicker toward the inside of the cylindrical side part, and the outer diameter of the cylindrical side part is open. The thin-walled portion has an elliptical shape with a roundness of 0.1 to 1.0 mm on a surface perpendicular to the axial direction of the cylindrical side portion.

It is preferable that the thin portion has a thickness of 0.125 to 0.270 mm.
The inner surface of the battery can is preferably covered with a conductive film.
The present invention also relates to an alkaline dry battery using the battery can.

  According to the present invention, since the contact state between the battery can and the positive electrode mixture is good, an alkaline dry battery excellent in heavy load discharge performance can be obtained.

One embodiment of the battery can of the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view of a battery can according to the present invention. FIG. 2 is a cross-sectional view of the thin portion of the battery can according to the present invention.
The bottomed cylindrical battery can 1 includes a cylindrical side portion 2, a bottom portion 3, and an opening portion 4. The cylindrical side part 2 includes a thin part 2a formed on the bottom part 3 side, a thick part 2b thicker than the thin part 2a formed on the opening part 4 side, a thick part 2b, and a thin part 2a. The boundary portion 2c is formed between the thin-walled portion and the thick-walled portion. The thick part 2b is thick toward the inside of the cylindrical side part 2, the outer diameter of the cylindrical side part 2 is the same from the opening part 4 to the bottom part 3, and the thin part 2a is the cylindrical side. A plane perpendicular to the axial direction of the portion 2 (direction X in FIG. 1), that is, the cross section shown in FIG. 2, is elliptical.

The thin-walled portion 2a corresponds to a portion where the positive electrode mixture is inscribed, and the thick-walled portion 2b corresponds to a portion that seals by sealing the sealing body via a gasket.
By making the thin-walled portion 2a elliptical, the positive electrode mixture and the cylindrical side portion of the battery can can be reliably in contact with each other at a portion where the inner diameter of the elliptical shape is small. In a battery using this battery can, excellent heavy load discharge performance can be obtained.

The roundness of the thin part 2a that is elliptical in the plane perpendicular to the axial direction X of the cylindrical side part 2 is 0.1 to 1.0 mm.
Roundness refers to the magnitude of deviation from a geometrically correct circle (geometric circle) of a circular shape, as defined in JIS B 0621. Roundness is expressed as the difference between the radii of two circles when the distance between the two concentric circles is minimized when the circular shape is sandwiched between two concentric geometric circles.

  When the roundness is less than 0.1 mm, the clearance between the battery can and the positive electrode mixture increases, the internal resistance of the battery increases, and the heavy load discharge performance decreases. On the other hand, when the roundness exceeds 1.0 mm, the clearance between the battery can and the positive electrode mixture becomes small, so when the positive electrode mixture is stored in the battery can, the positive electrode mixture cracks, and the battery performance May adversely affect.

It is preferable that the thickness T1 of the thin portion 2a is 0.125 to 0.270 mm.
If the thickness T1 of the thin wall portion is less than 0.125 mm, the strength of the thin wall portion decreases, so that the ovalization process can be performed only to a roundness of 0.1 mm, and the clearance between the battery can and the positive electrode mixture is reduced. It becomes large and the internal resistance of the battery tends to increase. On the other hand, when the thickness of the thin portion exceeds 0.270 mm, the thin portion becomes thick, and the effect of increasing the internal volume of the battery can by reducing the thickness of the thin portion becomes small.

The thickness T2 of the thick part 2b is preferably 0.150 to 0.50 mm.
If the thickness T2 of the thick wall portion is less than 0.15 mm, the strength of the battery can sealing portion is insufficient, the battery can easily be deformed by a strong impact such as dropping, and liquid leakage may occur. On the other hand, when the thick portion exceeds 0.50 mm, it is difficult to perform caulking.
As for the length of the thick part 2b in the axial direction X of the cylindrical side part 2, 6-12 mm is preferable as length which covers the sealing part of a battery.

In order to further improve the electrical contact state between the battery can and the positive electrode mixture, it is preferable to cover the inner surface of the battery can with a conductive coating. For example, it is preferable to form a graphite coating as a conductive coating by applying a graphite coating to the inner surface of the battery can in a range of 1 to 5 g / cm ² . When the coating amount of the graphite paint is less than 1 g / cm ² , sufficient conductivity cannot be ensured. On the other hand, when the coating amount of the graphite paint exceeds 5 g / cm ² , it takes time to dry and the productivity is lowered.

  It is preferable to form a Ni layer on the inner surface of the battery can by performing Ni plating in order to suppress iron corrosion by the electrolytic solution. The thickness of the Ni layer is preferably 1 to 3 μm. If the thickness of the Ni layer is less than 1 μm, iron may corrode, generate gas, and the battery may leak. On the other hand, when the thickness of the Ni layer exceeds 3 μm, iron is completely covered with the Ni layer, so that the storage performance is deteriorated.

The battery can of the present invention can be obtained by the following method.
By DI method, it has a cylindrical side part, a bottom part, and an opening part, and the said cylindrical side part is a bottomed cylindrical shape consisting of a thin part formed on the bottom part side and a thick part formed on the opening part side. An intermediate of is prepared. The DI method will be described with reference to FIGS.
Using the molding die 7 and the molding punch 6, the cup-shaped can base material 5 is processed into a bottomed cylindrical intermediate body 8 shown in FIG. The forming die 7 has one drawing die 7a and ironing dies 7b to 7d arranged in three stages. While pressing with the forming punch 6, the can base material 5 is continuously passed through the hole of the die to perform one step of drawing and three steps of ironing at once.

  The intermediate body 8 includes a cylindrical side portion 2, a bottom portion 3, and an opening portion 4. The cylindrical side portion 2 includes a thin portion 2a formed on the bottom portion 3 side, a thick portion 2b that is formed on the opening 4 side, and is thicker than the thin portion 2a, and the thin portion 2a and the thick portion 2b. The boundary portion 2c is formed between the thin wall portion 2a and the thick wall portion 2b. The thick part 2b is thicker toward the inside of the cylindrical side part 2, the outer diameter of the cylindrical side part 2 is the same from the opening part 4 to the bottom part 3, and the cross section of the thin part 2a is As shown in FIG. 3, it is a perfect circle. The roundness of the thin portion 2a of the intermediate body 8 is 0.05 mm or less.

As the cup-shaped can base material 5, for example, a steel plate that is nickel-plated on one side or both sides is supplied to a press machine, punched into a predetermined shape, and obtained by a drawing method.
The forming punch 6 is provided in front of the can base material 5 and is inserted in the columnar can forming portion 6b for forming the thin portion 2a of the bottom portion 10 and the cylindrical side portion 2, and behind the can forming portion 6b. A cylindrical rear end portion 6a for forming the thick portion 2b, the diameter of which is smaller than that of the can forming portion 6b, and the rear end portion provided between the can forming portion 6b and the rear end portion 6a. The taper portion 6c for forming the boundary portion 2c has a diameter that gradually increases from 6a to the can forming portion 6b.

  The bottomed cylindrical intermediate body 8 whose cross section of the thin portion 2a obtained by the DI method is a perfect circle is passed between a pair of guides provided with a gap smaller than the outer diameter of the thick portion 2b. Thus, the battery can 1 is obtained by processing the cross section of the thin portion 2a into an ellipse as shown in FIG.

The positive electrode mixture inscribed in the battery can includes, for example, manganese dioxide as a positive electrode active material and graphite as a conductive agent. The weight ratio of manganese dioxide (M) to graphite (C) (hereinafter referred to as M / C) in the positive electrode mixture is preferably 9 to 15.7. When M / C is less than 9, the amount of manganese dioxide as the active material is decreased, and the battery capacity is decreased. On the other hand, when M / C exceeds 15.7, the conductivity of the positive electrode mixture decreases.
Examples of the present invention will be described in detail below, but the present invention is not limited to the following examples.

Example 1
(1) Production of Battery Can By applying Ni plating, a steel plate having a Ni layer with a thickness of 2 μm formed on both sides was punched out in a circular shape to obtain a cup-shaped can base material. This can base material is made up of an opening, a bottom, and a cylindrical side portion by a DI method using the same molding punch and molding die as in FIGS. 4 and 5, and the cylindrical side portion is formed on the bottom side. And the cylindrical intermediate body which consists of a thick part formed in the opening part side was obtained.

By passing the thin part of the intermediate body obtained above through a pair of guides having a gap smaller than the outer diameter of the thick part, the cross section of the thin part is made elliptical and a bottomed cylindrical shape The same battery can as in FIG. 1 was obtained.
Thereafter, a graphite coating was applied to the inner surface of the battery can at a rate of 3.5 g / cm ² to form a conductive film containing graphite.

(2) Preparation of positive electrode mixture Manganese dioxide and graphite were mixed so that the weight ratio of manganese dioxide to graphite was 12.3. And this mixture and 40 weight% potassium hydroxide aqueous solution as alkaline electrolyte were mixed by the weight ratio of 100: 3, and after fully stirring, it compression-molded to flake shape. Next, the flaky positive electrode mixture was pulverized into granules, classified by a sieve, and pressed into a hollow cylinder to obtain a pellet-shaped positive electrode mixture.

(3) Preparation of gelled negative electrode Sodium polyacrylate as a gelling agent, 40 wt% aqueous potassium hydroxide solution as an alkaline electrolyte, and zinc alloy powder as a negative electrode active material were mixed at a weight ratio of 1:33:66. Thus, a gelled negative electrode was obtained. The zinc alloy powder used was an Al content of 100 ppm, a Bi content of 500 ppm, and an In content of 500 ppm.

(4) Assembly of cylindrical alkaline battery A single alkaline battery (LR20) having the structure shown in FIG. 6 was produced according to the following procedure. FIG. 6 is a front view with a cross section of a part of a cylindrical alkaline battery. The size of the battery can 1 was 32 mm in outer diameter and 65 mm in height. Moreover, the length of the thick part 2b in the axial direction X of the cylindrical side part 2 was 10 mm, the length of the boundary part 2c was 4 mm, and the length of the thin part 2a was 51 mm.
The battery can 1 was filled with a plurality of short cylindrical positive electrode mixtures 13. The positive electrode mixture 13 is composed of manganese dioxide and graphite, which are main constituent materials, and contains an alkaline electrolyte. At this time, the positive electrode mixture 13 was brought into contact with the conductive coating 12 formed on the inner surface of the battery can 1.

  A separator 14 and a bottom paper 15 were disposed on the hollow inner surface of the positive electrode mixture 13 and the inner surface of the bottom of the battery can, respectively. A predetermined amount of 40% by weight potassium hydroxide aqueous solution was injected into the separator 14 as an alkaline electrolyte. After a predetermined time, the gelled negative electrode 16 obtained above was filled in the separator 14. In addition, the separator 14 used the nonwoven fabric which mixed and mixed mainly the polyvinyl alcohol fiber and the rayon fiber.

  Next, the negative electrode current collector 10 was inserted into the center of the gelled negative electrode 16. The negative electrode current collector 10 is assembled integrally with a resin sealing member 17, a bottom plate 18 that also serves as a negative electrode terminal, and an insulating washer 19. And the opening part was sealed by crimping the opening edge part of the battery can 1 to the peripheral part of the baseplate 18 via the peripheral edge part of the sealing body 17. FIG. Finally, the outer surface of the battery can 1 was covered with the exterior label 11. In this way, an alkaline battery was completed.

At the time of manufacturing the battery, the thickness of the thick portion of the cylindrical side portion of the battery can is 0.3 mm, and the roundness and thickness of the thin portion of the cylindrical side portion are variously shown in Table 1. It changed and produced battery AK, respectively.
In battery A, a conventional battery can having a constant cylindrical side thickness was used. A battery K having the same configuration as that of the battery D was produced except that a conductive coating film was not formed on the inner surface of the battery can. In batteries A, B, and G, the cylindrical side portion of the battery can was not ovalized.
The roundness of the thin wall portion of the cylindrical side portion was adjusted by changing the dimension of the guide gap. Moreover, the thickness of the thin part of the cylindrical side part was adjusted by changing the diameter of the can forming part of the forming punch.

  The roundness is measured in accordance with JIS B 7451 using a contact type roundness measuring machine (Round Com 20A, roundness measuring machine manufactured by Tokyo Seimitsu Co., Ltd.). The roundness of the thin portion 2a was measured. In the present embodiment, a location located at a distance of 20 mm from the opening downward (bottom side) was measured and measured at an enlargement factor of 200. However, the measurement location may be any portion of the thin portion 2a, or even at one location. Within the scope of the present invention, the effects of the present invention described above can be obtained.

[Evaluation]
(5) Measurement of internal resistance of battery Twenty batteries were prepared in an environment of 20 ° C., the internal resistance of the battery was measured by a four-terminal AC measurement method, and an average value and a standard deviation were obtained.
(6) Evaluation of battery discharge performance Under a 20 ° C environment, each battery is continuously discharged at a current value of 1000 mA (heavy load) or 10 mA (light load), and the discharge continues until the closed circuit voltage reaches 0.9V. I checked the time.
The measurement results are shown in Table 1. In addition, the discharge duration in Table 1 was expressed as an index with the discharge duration of the battery A as 100. The batteries C to E and H to K in Table 1 are the batteries of the examples of the present invention.

  In the batteries C to E in which the roundness of the cylindrical side portion in the battery can is 0.1 to 1.0 mm, the clearance between the positive electrode mixture and the battery can decreases as the roundness increases. The average value of the internal resistance of the battery was reduced, and excellent light load and heavy load discharge performance was obtained.

  In the battery B in which the roundness of the cylindrical side portion is 0.05 mm or less, the clearance between the positive electrode mixture and the battery can is large, so that the internal resistance of the battery increases and the heavy load discharge performance decreases. Further, in the battery F in which the roundness of the cylindrical side portion is 1.2 mm, the clearance between the battery can and the positive electrode mixture is reduced, and the positive electrode mixture is cracked when stored in the battery can. As a result, the heavy load discharge performance deteriorated. Comparing the batteries C to F with the roundness changed with the thickness of the battery can constant, the larger the roundness, the smaller the clearance between the battery can and the positive electrode mixture, and the average value of the internal resistance is Although it decreases, cracks are likely to occur in the positive electrode mixture, and the standard deviation value of the internal resistance increases.

In the batteries I and J in which the thickness of the thin portion of the cylindrical side portion is 0.125 to 0.27 mm, excellent light load and heavy load discharge performance was obtained. In the battery H in which the thickness of the thin portion was 0.1 mm, the clearance between the positive electrode mixture and the battery can increased, the battery internal resistance increased, and the heavy load discharge performance slightly decreased.
Battery D, which has a conductive coating on the inner surface of the battery can, has a reduced internal resistance of the battery and improved heavy load discharge performance as compared to battery K which does not have a conductive coating on the inner surface of the battery can.

Example 2
An alkaline dry battery was produced in the same manner as in Example 1 except that the battery size was AA (LR6). The size of the battery can was 13.5 mm in outer diameter and 55 mm in height. Moreover, the length of the thick part in the cylindrical side part was 10 mm, the length of the boundary part was 4 mm, and the length of the thin part was 41 mm.

The thickness of the thick part in the cylindrical side part of the battery can is 0.2 mm, and the roundness and thickness of the thin part in the cylindrical side part are variously changed as shown in Table 2 to change the batteries L to P. Produced. In the battery L, a conventional battery can having a constant cylindrical side portion thickness was used. In the battery cans of the batteries L and M, the cylindrical side portion was not ovalized.
These evaluation results are shown in Table 2. In addition, the discharge duration in Table 2 was expressed as an index with the discharge duration of the battery L as 100. The batteries N and O in Table 2 are the batteries of the examples of the present invention.

  Batteries N and O using battery cans having a roundness of 0.1 to 1.0 mm at the thin-walled portion obtained excellent light load and heavy load discharge performance.

  In the battery M in which the roundness of the cylindrical side portion is 0.05 mm or less, the clearance between the positive electrode mixture and the battery can is large, so that the internal resistance of the battery increases and the heavy load discharge performance decreases. In addition, in the battery P in which the roundness of the cylindrical side portion is 1.2 mm, the clearance between the battery can and the positive electrode mixture is reduced, and the positive electrode mixture is cracked when stored in the battery can. As a result, the heavy load discharge performance deteriorated.

Example 3
An alkaline dry battery was produced in the same manner as in Example 1 except that the battery size was single 2 (LR14). The size of the battery can was 24 mm in outer diameter and 50 mm in height. Moreover, the length of the thick part in a cylindrical side part was 10 mm, the length of the boundary part was 4 mm, and the length of the thin part was 36 mm.

The thickness of the thick wall portion in the cylindrical side portion of the battery can is set to 0.3 mm, and the roundness and thickness of the thin wall portion in the cylindrical side portion are variously changed as shown in Table 3 to change the batteries Q to U. Produced. For battery Q, a conventional battery can with a cylindrical side portion having a constant thickness was used. In the battery cans of the batteries Q and R, the cylindrical side portion was not ovalized.
These evaluation results are shown in Table 3. In addition, the discharge duration in Table 3 was expressed as an index with the discharge duration of the battery Q as 100. The batteries S and T in Table 3 are the batteries of the examples of the present invention.

  In the batteries S and T using the battery can having a roundness of 0.1 to 1.0 mm at the thin wall portion, excellent light load and heavy load discharge performance was obtained.

  In the battery R in which the roundness of the cylindrical side portion is 0.05 mm or less, the clearance between the positive electrode mixture and the battery can is large, so that the internal resistance of the battery is increased and the heavy load discharge performance is deteriorated. In addition, in the battery U in which the roundness of the cylindrical side portion is 1.2 mm, the clearance between the battery can and the positive electrode mixture is reduced, and the positive electrode mixture is cracked when stored in the battery can. As a result, the heavy load discharge performance deteriorated.

  The alkaline dry battery of the present invention is suitably used as a power source for electronic devices such as portable devices and information devices.

It is a longitudinal cross-sectional view of an example of the battery can of this invention. It is a cross-sectional view of the thin part in the cylindrical side part of the battery can of this invention. It is a cross-sectional view of the thin part in the cylindrical side part of an intermediate body. It is a longitudinal cross-sectional view which shows DI process for obtaining an intermediate body. It is a longitudinal cross-sectional view which shows the state by which the intermediate body was obtained by DI process. It is the front view which made a part of alkaline dry battery of the present invention a section.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery can 2 Cylindrical side part 2a Thin part 2b Thick part 2c Boundary part 3 Bottom part 4 Opening part 5 Can base material 6 Molding punch 6a Rear end part 6b Can formation part 6c Taper part 7 Molding die 7a Drawing die 7b, 7c 7d Ironing die 8 Intermediate 10 Negative electrode current collector 11 Exterior label 12 Conductive coating 13 Positive electrode mixture 14 Separator 15 Insulating cap 16 Gelled negative electrode 17 Sealing body 18 Bottom plate 19 Insulating washer

Claims (4)

A bottomed cylindrical battery can having a cylindrical side, a bottom, and an opening,
The cylindrical side portion is composed of a thin portion formed on the bottom side and a thick portion thicker than the thin portion formed on the opening side,
The thick part is thick toward the inside of the cylindrical side part, and the outer diameter of the cylindrical side part is the same dimension from the opening part to the bottom part,
The battery can according to claim 1, wherein the thin portion is an ellipse having a roundness of 0.1 to 1.0 mm on a surface perpendicular to the axial direction of the cylindrical side portion.   The battery can according to claim 1, wherein the thin portion has a thickness of 0.125 to 0.270 mm.   The battery can according to claim 1, wherein an inner surface of the battery can is covered with a conductive film. An alkaline dry battery using the battery can according to claim 1.

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