JPH09312150A - Cylindrical battery case and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery case with its superior pressure resistance at a sealing port and a manufacturing method thereof. SOLUTION: A base material 1 of a metal case is made of a steel plate applied with nickel plating or nickel alloy plating, a thickness A of an opening of the metal case exceeds the thickness of the base material and is within the range of 120% or less of the thickness of this base material, a thickness of a bellow part of the metal case is within the range of 60 to 10% of the thickness of the base material, and a Vickers hardness of the opening of the metal case is within the range of 100 to 200kg/m<2> . In manufacturing this metal case, the base material is drawn by using a first punch 3 forming a clearance of 1.2 to 1.5 of the plate thickness of the base material between a dice 2 and a punch 3, whereby the plate thickness of the opening of the base material is stressed and deformed to a plate thickness exceeding the thickness of the base material, and an intermediate case 1a is formed. Then, while an inner circumference face of the intermediate case is held by means of a blank holder 5 using a second dice 4 and a second punch 6 having a smaller clearance than the plate thickness, the intermediate case is made through drawing and ironing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal case for a cylindrical battery, which contains a power generating element composed of a positive electrode, a negative electrode and an electrolytic solution, and a method for manufacturing the same, more specifically, an opening and a body. The present invention relates to a metal case for a battery having different wall thicknesses and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a metal case for a battery in which the thickness of the opening and the thickness of the body are changed, that disclosed in Japanese Patent Publication No. 7-99686 is known. This known one was prepared by using a nickel-plated iron cup with a diameter larger than the desired outer diameter of the can as a raw material, successively squeezing it, and arranging coaxially in multiple stages so that the ironing outer diameter became smaller. The battery case is obtained by supplying the iron to a plurality of ironing dies and punching them into a die having a desired outer diameter of the squeezing iron with a punch to continuously pass the iron.

[0003]

However, in this known battery case, since the wall thickness of the body is gradually reduced from the bottom to the opening with respect to the thickness of the base material, this case is used. When a battery is formed by using the battery, there is a problem in that the pressure resistance of the sealing portion cannot be sufficiently secured when gas is generated inside the battery because the thickness of the opening is relatively thin.

Further, in the case of the battery case formed by the above-mentioned known method, the roughness of the inner surface of the body is mirror-finished to 1 μm to 2 μm, and the contact resistance between the inner surface of the body and the positive electrode mixture increases, There is a problem that it causes deterioration of battery characteristics.

Therefore, a first object of the present invention is to solve the above-mentioned conventional problems and to provide a battery case excellent in pressure resistance of a sealing portion and a manufacturing method thereof.

A second object of the present invention is to provide a battery case in which the inner surface of the body has a relatively large roughness and the contact resistance between the inner surface of the body and the positive electrode mixture can be reduced to improve the battery characteristics. There is in providing the manufacturing method.

[0007]

In order to achieve the above object, in the present invention, in a metal case for a tubular battery in which a power generating element consisting of a positive electrode, a negative electrode and an electrolytic solution is filled, the base material of the metal case is The thickness of the opening of the metal case exceeds the thickness of the base material and is within 120% or less of the thickness of the base material, and the thickness of the body of the metal case is the thickness of the base material. Sano 6
The Vickers hardness of the opening of the metal case is in the range of 0 to 100%, and the Vickers hardness of the opening of the metal case is in the range of 100 to 200 kg / m ² .

As a result, according to the present invention, a large sealing strength can be obtained even if the metal case for a battery is formed by using a relatively thin base material.

Further, in the present invention, preferably, a metal case base material is a nickel-plated or nickel alloy-plated steel plate, and the inner surface roughness (R ₁ ) of the opening of the metal case is the inner surface of the body. Roughness (R ₂ ) or less, and inner surface roughness (R ₁ ) of the opening is 2 μm or less in terms of maximum height (Rmax) according to JISB0601.

As a result, in the battery metal case of the present invention, sufficient liquid-tightness can be obtained in the opening portion, while the contact resistance with the positive electrode mixture in the body portion is reduced as compared with the conventional case, and the battery performance can be improved. it can.

Further, in the method of the present invention, a cold-rolled steel plate base material plated with nickel or nickel alloy is placed on the upper surface of the first die, and the plate of the base material is placed between the inner surface and the inner surface of the die. The thickness of the opening of the base material exceeds the thickness of the base material by drawing the base material with a first punch forming a clearance of 1.2 to 1.5 of the thickness. To form an intermediate case by stress deformation, and then the second intermediate case having a clearance smaller than the plate thickness.
Using the die and the second punch, the intermediate case is squeezed and ironed while the inner peripheral surface of the intermediate case is pressed by the blank holder.

By this method, according to the present invention, it is possible to obtain a metal case for a battery having excellent sealing property, liquid tightness and low contact resistance with the positive electrode mixture as described above.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION First, a method for manufacturing a cylindrical battery case according to the present invention will be described with reference to the attached FIG.

In FIG. 1A, reference numeral 1 indicates a steel plate base material for forming the metal case for a battery according to the present invention. This steel plate substrate has nickel plating or Ni on both sides.
It is plated with a nickel alloy such as —Co or Ni—Ag. In this example, the plated steel plate base material 1 has a thickness of 0.25 mm. The steel plate base material 1 is placed on the upper surface of the first die 2 as a flat circular blank having a diameter of about 60 mm, and the punch 3 is located above it. The dimensional relationship is such that a clearance of 1.2 to 1.5 times the wall thickness of the steel plate substrate 1 is formed between the outer diameter of the punch 3 and the inner diameter of the first die 2.

From the state shown in FIG. 1 (a), the first punch 3 is lowered and the steel sheet base material 1 is drawn by the first die 2 as shown in FIG. 1 (b) to form the intermediate drawing case 1a. obtain. At the time of this drawing, the outer edge portion A of the steel sheet base material 1 is subjected to compressive stress due to the upper inner peripheral edge of the first die and the wall thickness increases from 3% to 20%.

Next, as shown in FIG. 1C, the intermediate squeeze case 1a formed as described above is used as a second die 4.
Installed on the upper side, the inner peripheral surface of the intermediate diaphragm case is pressed by the blank holder 5, and the body of the case is squeezed by the second punch 6 so as to obtain the battery case 7. In this case, the second
The clearance between the inner diameter of the die 4 and the outer diameter of the second punch 6 is set to be smaller than the wall thickness of the base material 1, so that only the body portion of the battery case is drawn and squeezed. . At this time, the wall thickness of the body can be changed by adjusting the clearance, but when the wall thickness of the body is less than 60% of the base material, the positive electrode mixture is inserted or the sealing portion is caulked. Swelling and deformation occur in the process, causing problems in strength, so the thickness is 60% of the base material.
It is necessary to do above. On the other hand, considering the discharge performance of the battery, reducing the thickness of the can body has the advantage of increasing the amount of positive electrode active material. However, in actual discharge, a remarkable effect was obtained when the thickness of the can body portion was 85% or less of the thickness of the base material. Therefore, the thickness of the can body is preferably 60 to 85% of the thickness of the base material.

Next, as shown in FIG. 1D, the opening of the battery case 7 is set in the opening of the third die 9, and the opening of the battery case is expanded by the third punch 9. .

The metal case formed as described above finally has a top end opening A in FIG.
The inverted "H" -shaped end portion above the thick portion is horizontally cut from the inside to the outside and used as a battery case.

In FIG. 1 (c), the portion of the inner peripheral surface of the intermediate throttle case held by the blank holder 5 is shown as an enlarged step for convenience of explanation, but in reality, this step is expanded by about 1 mm in the radial direction. It is opened, and the upper part of this step becomes the opening of the battery case, and when sealed, it is squeezed inward in the radial direction to have the same diameter as the body below the step.

In the above method of the present invention, when the intermediate drawing case 1a is formed by drawing a steel plate base material, the opening end portion of the battery case is subjected to compressive stress and is larger than the wall thickness of the base material. 2 shows the relationship between the wall thickness of the opening end of the case and the withstand voltage of the battery. It should be noted that FIG. 2 shows an index with 100 as the sealing strength when the wall thickness of the open end of the battery case is equal to the wall thickness of the base material.

As is apparent from FIG. 2, in the battery case made according to the present invention, the wall thickness of the open end is less than the wall thickness of the base material.
Since it exceeds about 100% and is about 120%, the pressure resistance at the sealing portion is remarkably improved as compared with the conventional one in which the wall thickness of the opening end is 100% or less of the wall thickness of the base material. I understand. Here, when the wall thickness exceeds 110%, the sealing strength hardly changes, but it is considered that this is rather due to the deformation of the negative electrode terminal plate.

When measuring the sealing strength, the positive electrode battery case was emptied with the positive electrode mixture, the negative electrode active material, the separator and the electrolytic solution, and the open end of the positive electrode battery case was put through a gasket. A crimped negative electrode terminal plate was prepared, and a small hole was formed in the other end of the positive electrode battery case, and pressurized gas was supplied from the small hole to determine the pressure at which the battery opening breaks.

In the above method of the present invention, the step of forming the intermediate drawing case 1a by drawing the steel plate base material 1,
Since the metal case for the battery is formed separately from the process of squeezing and ironing the body of the intermediate drawing case, it is possible to continuously iron up to the metal case processed with multiple ironing dies arranged in multiple stages on the same axis. Work hardening can be reduced as compared with the method described above.

FIG. 3A shows the relationship between the increase in Vickers hardness due to work hardening of the case opening and the rate of change in the axial height dimension of the battery. The axial height of this battery is shown in Fig. 3.
It is the dimension L shown in (b). As is clear from FIG. 3 (a), the Vickers hardness is 2 due to work hardening.
If it exceeds 00 kg / m ² , the open end of the battery metal can tends to return to the state before processing due to springback, and the sealing strength of the battery is expected to decrease, which is not preferable.

In the present invention, since the battery metal case is formed in several steps as described above, the work hardening due to the drawing process of the battery case opening is suppressed, and the hardness of the opening is set to the base material. The Vickers hardness of about 100 kg / m ² to the Vickers hardness of 200 kg / m ² can be maintained.

Further, in the method of the present invention, in particular, FIG.
As shown in FIG. 5, in order to thin the case body by simultaneously performing drawing and ironing of the intermediate drawing case 1a while pulling using the blank holder 5, as compared with the known method described in the conventional example, Surface roughness (1 μm-2
It is possible to obtain a surface roughness (2 μm to 10 μm) greater than (less than μm). The surface roughness here is JIS B
0601-1982, the surface roughness was measured by a stylus measuring instrument, and the surface roughness was indicated by Rmax and Rz.

FIG. 4 shows the results of measurement of the effects of the inner surface roughness of the opening of the battery case and the inner surface of the body on the leakage rate of the electrolyte from the positive electrode side and the constant current discharge time. From FIG. 4, when the surface roughness of the body is large, the discharge time is long. It is considered that this is because the contact resistance between the inner surface of the battery case and the positive electrode mixture is reduced, and it is understood that the surface roughness of the body is preferably 4 μm or more. Also,
It is preferable that the opening have a surface roughness as small as possible because the adhesion to the gasket is good and the liquid leakage rate is low.
It is to be less than μm.

In the present invention, when the drawing and ironing of the intermediate drawing case 1a are simultaneously performed while pulling as described above, it is not possible to change the processing conditions so that the inner surface roughness of the body portion becomes, for example, 4 μm or more. It's easy. In addition, as shown in FIG. 1B, the opening of the battery case has the outer surface of the steel plate base material 1 narrowed down by the upper end of the inner circumference of the die 2 to increase its wall thickness, and the inner surface of the opening is shown in FIG. 1D. By expanding the opening with punch 8 and die 9 as shown,
It is easy to set the surface roughness to 2 μm or less.

[0029]

As described above, in the tubular battery metal case of the present invention, the base material of the metal case is made of a steel plate, and the thickness of the opening of the metal case exceeds the thickness of the base material. Since the thickness is within 120% or less of the thickness of the material, a large sealing strength can be obtained, or a sealing strength similar to the conventional one can be obtained by using a base material thinner than the conventional one. It is possible to go down. Further, the thickness of the body of the metal case is 60 to 10 of the thickness of the base material.
Since it is within the range of 0%, there is no risk of swelling or deformation at the time of inserting the positive electrode mixture or in the processing step of crimping the sealing portion. Further, since the Vickers hardness of the opening of the metal case is in the range of 100 to 200 kg / m ² , there is almost no springback at the opening end of the metal can for batteries, and it is possible to maintain a suitable battery sealing strength. .

In the present invention, the base material of the metal case is made of a steel plate plated with nickel or nickel alloy, and the inner surface roughness (R ₁ ) of the opening of the metal case is the inner surface roughness ( R ₂ ) or less, and the inner surface roughness (R ₁ ) of the opening is the maximum height (Rma) according to JIS B 0601.
When the value of x) is 2 μm or less, sufficient liquid-tightness can be obtained at the opening of the metal case for the battery, while the contact resistance with the positive electrode mixture at the body is lower than in the conventional case and battery performance is improved. Can be improved.

Further, the method of the present invention is a method suitable for obtaining a metal case for a battery, which has excellent sealing properties, liquid tightness, and low contact resistance with the positive electrode mixture as described above.

[Brief description of drawings]

FIG. 1 shows a method of manufacturing a tubular battery case according to the present invention in the order of steps, (a) shows a state before processing a steel plate base material with a first die and a punch, and (b) shows an intermediate drawing case. FIG. 3C is a diagram showing a process of forming a battery, FIG. 7C is a state in which a body of a battery case is drawn and ironed, and FIG. is there.

FIG. 2 is a diagram showing a relationship between a wall thickness of an opening end of a case and a withstand voltage of a battery.

FIG. 3 is a diagram showing the relationship between the increase in Vickers hardness and the rate of change in the axial height dimension of the battery.
(B) is a figure which shows the axial height dimension of a battery.

FIG. 4 is a diagram showing the results of measurement of the influence of the inner surface roughness of the opening of the battery case and the inner surface of the body on the leakage rate of the electrolytic solution from the positive electrode side and the constant current discharge time.

[Explanation of symbols]

 1 Steel plate base material 2 1st die 3 1st punch 4 2nd die 5 Blank holder 6 2nd punch 7 Battery case A Outer edge part of a thick steel plate base material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Hashino 41 Kamome-cho, Naka-ku, Yokohama, Kanagawa Daiichi Metal Industry Co., Ltd. (72) Naoki Miyasaka 41 Kamome-cho, Naka-ku, Yokohama, Kanagawa Daiichi Metal Industry Co., Ltd.

Claims (3)

[Claims] 1. A metal case for a tubular battery, which is filled with a power generating element composed of a positive electrode, a negative electrode and an electrolytic solution, wherein a base material (1) of the metal case is made of a steel plate, and an opening (A) of the metal case is used. The thickness of the substrate exceeds the thickness of the substrate by 1 of the thickness of the substrate.
20% or less, the thickness of the body of the metal case (7) is within the range of 60 to 100% of the thickness of the base material, and the Vickers hardness of the opening of the metal case is 100
A metal case for a cylindrical battery, which is in the range of up to 200 kg / m ² . 2. The substrate (1) of the metal case (7)
Is a steel plate plated with nickel or nickel alloy, and the inner surface roughness (R ₁ ) of the opening of the metal case (7) is not more than the inner surface roughness (R ₂ ) of the body, and the opening The metal case for a cylindrical battery according to claim 1, wherein the inner surface roughness (R ₁ ) of the portion is 2 μm or less in terms of the maximum height (Rmax) according to JIS B 0601. 3. A cold-rolled steel plate base material (1) plated with nickel or nickel alloy is first die (2).
The base material is drawn by using a first punch (3) which is installed on the upper surface of the die and forms a clearance of 1.2 to 1.5 times the plate thickness of the base material with the inner surface of the die. By doing so, the plate thickness of the opening of the base material is stress-deformed to a plate thickness exceeding the thickness of the base material to form the intermediate case (1a), and then the intermediate case has a clearance smaller than the plate thickness. A cylinder characterized in that the intermediate case is squeezed and ironed while pressing the inner peripheral surface of the intermediate case with a blank holder (5) using a second die (4) and a second punch (6). For manufacturing a battery case (7).