JPH04341754A - Manufacture of battery case - Google Patents

Abstract

PURPOSE:To provide a case manufacturing method with which pinholes are not produced in inner and outer surfaces of a battery case, with a nickel plating thickness secured stably. CONSTITUTION:A plate iron material 1 having nickel plating 2 of 3-5mum is preliminarily moulded like a cup larger than a desired case outer diameter regardless of a thickness of a material, and it is sent through multi-stages of dies disposed to set a throttling diameters smaller in order continuously using a punch. Heat generation reaching 600-800 deg.C at that time is used to hot- roll the nickel plating to obtain a final plating thickness of about 1.5-2.5mum on the inner and outer surface of the case.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a case for a battery, and more particularly, a case for an alkaline storage battery.

0002

2. Description of the Related Art Cases for alkaline storage batteries are required to be resistant to alkaline electrolytes and to ensure long-term electrical conductivity due to direct contact with power generation elements. For this reason, in alkaline storage battery cases, the inner surface of the case has traditionally been plated with nickel, and this is generally done after the iron case has been molded into a desired shape.

0003

However, in the plating process after forming the iron case into a desired shape, it is not possible to ensure a sufficient plating thickness, especially on the inner surface of the case, due to insufficient flow of the plating solution within the case. Furthermore, when a case is transfer-drawn from a pre-plated steel plate, it is not possible to ensure a uniform thickness of plating due to the effects of heat, especially on the inner wall of the case, resulting in the plating peeling off and exposing the iron base. As a result, the electrical contact between the case surface and the cathode plate inside the battery deteriorates, resulting in an increase in internal resistance and self-discharge.

0004

[Means for Solving the Problems] In order to solve the above-mentioned conventional problems, the present invention provides a preliminary method using plate iron material which has been previously plated with nickel to a thickness of 3 to 5 micrometers, into a cup shape larger than the desired case outer diameter. After molding, a plurality of dies are arranged coaxially so that the drawing diameter becomes smaller, and the die is pressurized with a punch and passed through the die, which is set to the outer diameter of the case to obtain the inner diameter of the final die. The nickel plating is hot-rolled by keeping the heat generation temperature of the peripheral wall of the cup-shaped iron base at 600 to 800°C during drawing and ironing, which is adjusted by the processing pressure and the reduction ratio of the ironing diameter of the multi-stage die. The present invention provides a method for manufacturing an alkaline storage battery case that can ensure a nickel plating thickness of 1.5 to 2.5 micrometers.

[0005]

[Function] As described above, according to the present invention, it is possible to obtain a case for an alkaline storage battery that has no pinholes on the inner surface of the case and has a stable nickel plating thickness of 1.5 to 2.5 micrometers. This makes it possible to suppress increases in internal resistance and self-discharge caused by the iron base being exposed on the inner surface.

[0006]

EXAMPLES The present invention will be explained in detail below by way of examples. First, a thin iron plate 1 as a base material is prepared, and nickel plating 2 is applied to both sides thereof. In this case, it is desirable that the thickness of the nickel plating 2 be approximately twice the desired plating thickness to be finally obtained. For this reason, in this example, the final nickel thickness of case 4 was set to approximately 1.5 micrometers, and five samples were prepared in which this iron base was plated with a thickness of approximately 3 micrometers (Figure 1 A). This case 4 is manufactured by the method shown in FIGS. 2(A) and 2(B). That is, it is pre-processed into a shallow cup shape (as shown by 3 in FIG. 1B) with a diameter larger than the desired outer diameter of the case.
This is sequentially drawn and ironed, and dies (b1), (b2), (b3), (
bn) is pressurized with a punch (c) and passed in sequence, and the drawing diameter of the final stage die (bn) is set as the desired outer diameter of the case, and the punch (c) is passed continuously and instantaneously. It will be done.

By applying this continuous drawing and ironing pressure, the elongation of the nickel plating 2 can follow the elongation of the iron during drawing and ironing.In particular, by adjusting the rate at which the die diameter gradually decreases, the inner wall of the case can be The exothermic temperature of 600-8
By maintaining the temperature at 00° C., a case could be obtained in which the plating 2 did not peel off. The thickness of the nickel plating at the center of the outer side wall of the obtained case 1 was 1.4 to 1.7 micrometers, that of the center of the inner side wall was 1.2 to 1.6 micrometers, and that of the inner bottom was 2.4 to 2 micrometers. It was possible to make the film as thick and uniform as .7 micrometers (C in Figure 1).

[0008] Using the case manufactured as described above, the anode plate and the cathode plate wound into a cylindrical shape with a separator interposed therebetween are inserted into the case according to the usual method, and after injecting the electrolyte. A sealed AA size nickel cadmium storage battery (X) was manufactured, and the following battery tests were conducted. For comparison, a battery prototype was made using a case with nickel plating instead of glass plating, which is the conventional formulation (Y
) were prepared and tested. The nickel plating thickness of the case was 1.8 to 2.2 micrometers at the center of the outer side wall, and 0.03 to 0.08 micrometer at the center of the inner side wall. In the battery test, the standard capacity was measured by charging at 0.1C, and then the battery was stored in a charged state for 14 days at 45°C, and then the internal resistance and discharge capacity, ie, self-discharge, of the battery were measured. (Table 1) shows the results, and FIG. 3 shows the relationship between the nickel plating thickness on the inner surface of the case and the discharge capacity ratio after storage at 45° C. for 14 days.

[0009]

[Table 1]

[0010] This data shows that if the thickness of the nickel plating inside the battery case is too thin, it will adversely affect internal resistance and self-discharge.

By using the case obtained according to the present invention, these problems could be effectively prevented. By comprehensively judging the above results, the thickness of the nickel plating on the inner surface of the case must be at least 1.0 micrometers or more.

0012

[Effects of the Invention] As described above, by using the method of manufacturing a battery case of the present invention, a case without pinholes and with a stable nickel plating thickness can be provided, and the internal resistance of the battery after storage can be increased. , contributes to suppressing the increase in self-discharge.

[Brief explanation of the drawing]

[Fig. 1] Explanatory diagram of changes in nickel plating thickness until a disc-shaped iron material is processed into a desired case A Cross-sectional view of the iron material B Cross-sectional view of a pre-processed product C Cross-sectional view of the case

[Figure 2] (A) Explanatory diagram when drawing a desired case from a dish-shaped cup material

Claims (1)

[Claims] [Claim 1] Cup-shaped iron bases whose inner and outer surfaces are nickel-plated to a thickness of 3.0 to 5.0 micrometers are arranged coaxially in multiple stages, and the cup-shaped iron bases are successively shaped into a case. While drawing and ironing, a die is set to the outer diameter of the case to obtain the final die inner diameter, and a single punch passes through these multi-stage dies to determine the final inner diameter of the case. The cup-shaped iron base is continuously processed into a case while maintaining the heat generation temperature during drawing and ironing of the peripheral wall at 600 to 800°C,
A method for manufacturing a battery case in which the thickness of nickel plating on the inner and outer surfaces of the case is 1.5 to 2.5 micrometers.