JPH01115052A - Squar-shaped sealed battery - Google Patents

Abstract

PURPOSE:To increase the fitting accuracy in a joint of a battery container to a cover and to prevent the generation of fine cracks in a welded part by using a steel plate having thin nickel layers on its both sides as the material plate of the battery container and the cover, and using the battery container manufactured by a forming method combining drawing with ironing. CONSTITUTION:A steel plate 1a having thin nickel layers, whose thickness is specified so as to have a specified thickness after formation, on both sides is formed in a squar-shaped battery container having a specified dimension by deep drawing. A cutout step 1c is formed in the battery container by drawing with ironing. A cover 2, having a plane periphery, manufactured by forming a steel plate having thin nickel layers 1b same as the battery container is put on the cutout step 1c of the battery container. The joint 7 of the outer periphery of the cover 2 and the opening edge of the battery container is sealed by laser welding. Since the cover is stably, accurately fitted to the opening of the battery container, laser welding is easily conducted and the joint 7 is locally, instantaneously melted by laser beams and a strain caused by the presence of the nickel layer during being cooled is retarded. The welded part 9 having no cracks is formed and a battery is surely sealed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rectangular sealed battery in which a joint between a battery container and a lid is sealed by laser welding.

[Prior art] - With the development of electronic devices, they have become smaller and thinner, and the sealed batteries used as their power sources are also required to be small, have high capacity density, and have excellent reliability. Improvements have also been made to sealing methods. In particular, for batteries that are built into devices and used for long periods of time, there is a strong demand for small, rectangular, internally thin batteries that are space efficient when stored, and their implementation is progressing. In the case of small prismatic sealed batteries, overcharging,
In order to withstand the internal gas pressure that occurs during overcharging, studies are underway to develop a structure in which a lid plate is fully fitted into a metal battery container and the joint is sealed by laser welding. In the case of a sealed battery using a laser welding sealing method, the following methods of fitting the battery container and the lid have been attempted in order to accommodate laser welding.

FIG. 6 shows a cross section of the main part of the side surface, and shows the battery container 31.
A method of inserting a flat plate-like lid 33 into the frontispiece, which has the same size as the inside dimension of the mouth rim and has a small arc or taper 33a on the lower surface of the periphery of the lid as necessary (FIG. 5A), or a special method. The battery container 31 is equipped with a lid 43 having a stepped portion 43a on the periphery, as seen in Japanese Patent Publication No. 143284/1984.
There is a method of placing the battery on the frontispiece (Fig. 6), but in the case of small square batteries, the method shown in Fig. 6 is a lid body 4 made by cutting etc.
3 has problems such as low productivity and large thickness.

As will be described later in the case of FIG. 5A, there are problems with the shape and accuracy when molding the battery container 31, especially when the lid is thin, it is difficult to insert it horizontally into the lip of the battery container. It was difficult and unproductive, so it was only used for certain things. Therefore, as disclosed in Japanese Unexamined Patent Publication No. 56-107470, for example, as shown in the sectional view of the main part in FIG.
In the above publication, stainless steel is used as the material for the battery container and the lid, and the battery is fitted so that a is in contact with the inner edge of the opening end of a cylindrical or thin plate-shaped battery container. A method has often been used in which a laser beam 63 is irradiated from above the joint between the container and the lid to weld and seal the joint.

In the case of a rectangular battery, a rising portion may be formed only on two opposing sides of the periphery of the lid toward the inside of the battery (not shown),
There is also a method in which the battery case is fitted and fixed at a predetermined position at the open end of the battery container using the rising portion as a guide, and then the fitted joint is welded and sealed.

Problems to be Solved by the Invention In such a conventional configuration, as disclosed in Japanese Patent Application Laid-Open No. 6-74964, when sealing the υ battery container by laser bath contact, localized Since welding can be done instantaneously, the thermal effect on the battery body is extremely low and high-precision welding is possible.On the other hand, the laser beam has good straightness and the focal area is extremely small. , the joint 9 formed by the open end of the battery container, which is the surface to be welded, and the periphery of the lid or the end face of the upright part, may result in incomplete welding due to the influence of the shape, precision, material, etc. There were cases where a sealed state could not be obtained.

The first problem is how to ensure the surface metal precision required for laser welding when the battery container and lid are fitted together. Conventionally, parts such as battery containers and lids of this type of battery have generally been made by cutting or trimming steel plates etc. from the viewpoint of productivity, as shown in Japanese Patent Laid-Open No. 67-145265. It is made using the drawing method used. As shown in the top view of FIG. 7, when a rectangular battery container is formed by the drawing method described above, the thickness is uneven at the corners, and the straight portion 31a becomes thinner and tends to curve outward. As a result, the lid body (straight line) creates a gap G1. In addition, in order to ensure moldability, it is necessary to provide relatively large circular arcs 31b at the corners as shown in the figure, but it is difficult to ensure the shape and size accuracy. When a rising portion is provided for the lid, the problem is similar to that of the battery container, although the problem is somewhat alleviated because the height of the rising portion is low. Therefore, when the battery container 51 and the lid body are fitted together, as shown in the cross section of the main part in FIG.
A gap G2 in the order of 0.1 to 0.3 is generated in most of the joints. As a result, the lid body is tilted and the joint portions are misaligned.

Alternatively, there is a problem in that the welding material falls below a predetermined position, making welding difficult.

When using the flat plate-shaped lid 33 shown in FIG. 5A, the circumference R of the lid
Although this is slightly improved by punching out with high precision, the same problem as above occurred. As stated in Japanese Patent Laid-Open No. 57-74964, etc., if the bonding surfaces of the battery container and the lid's upright portion become insufficiently adhered, and a gap is created in the bonded portion, the straightness may deteriorate. During this time, a good laser beam passes through pJt, damaging the internal battery elements or causing incomplete welding, making it difficult to obtain a sufficient seal.

When the above joint surfaces are welded and sealed with a laser beam,
As can be seen from the above description, it is required that the joint surfaces be flat without discrepancies, and that the gap between the joints be as small as possible. The weldable gap, for example, G2 in FIG.
Regulatory standards such as m+ or less are shown, but if you consider stability when fitting the lid and productivity during welding (processing speed, defect rate), the gap should be approximately 0°1-0.05 wsi or less. It is necessary to

Observing the above-mentioned welding state, as seen in the side cross section of the eighth fixed part, the joint between the inner edge of the open end of the battery container 31 and the peripheral edge of the lid body 33 is melted by the laser beam 34, and the welded part 3
4, if a gap G1 exists in the joint, the weld will sag as shown in the figure, and the penetration depth dl will tend to be shallow and the weld strength will tend to decrease. A slight improvement can be seen by increasing the power and slowing down the welding speed. However, when the gap G1 exceeds 0.01 mm, problems arise such as air bubbles being generated in the welded part and parts of the welded part hanging down and falling off when melted, resulting in poor sealing. As one of the countermeasures, as shown in Japanese Utility Model Application Publication No. 69-192261, the inner dimensions of the battery container are made slightly smaller than the outer dimensions of the lid, as shown in Fig. 6B or Fig. 12. (Outer diameter of the rising part of the lid φ2>Inner diameter of the battery container 61 φ1) shape.

Due to precision issues and the edges of the opening end of the container not being able to fit into the lid during press-fitting, the lid partially lifts up. Otherwise, it was easy to sink into the container. When molding the battery container 31 shown in FIG. 7, if a multi-stage correction process is added to correct the deformation and the combination with the lid is selected, some products with good fit can be obtained. However, both workability and productivity were low, making it difficult to apply to production. Also, as an application of the container shape for button-type alkaline batteries, etc., the first
3. As shown in the cross-sectional view of the fixing part, when the rectangular battery container 61 having a stepped portion 61a with corrugations near the mouth edge is drawn, the lid 62 can be stably inserted, but the battery container 61 The machining shape and accuracy could not be improved, the effect of reducing the gap G3 was low, and there was a problem that the outer shape of the rim of the container became large.

Therefore, as an improvement measure to completely improve the fit between the prismatic battery container and the lid, the cylindrical battery of Utility Model Publication No. 36-26438 or the square battery molded by the injection molding method of Utility Model Publication No. 37-14961, etc. A method of removing part of the wall thickness of a resin battery case to form a stepped part on which the lid is placed, such as a resin battery case. An attempt was made to form a stepped portion by cutting with a milling machine or the like while correcting the shape using a tool, but deformation during processing and irregularities in the shape of the corners easily occurred, resulting in poor productivity and difficulty in application.

The second problem relates to surface coating materials such as nickel plating when steel plates are used as the material for the battery container and lid. For rectangular battery containers, materials with good workability during molding are required, and depending on the application, materials are molded from steel and nickel plated on the surface for reasons such as lowering the contact resistance inside and outside the battery and preventing surface rust. It was often necessary to use what had been prepared. However, when the battery container and the lid are molded from a steel plate and then nickel plated by barrel plating, etc., the thickness of the plating near the open end of the battery container and the periphery of the lid becomes large. The thickness unevenness tends to be larger than that in other parts, which lowers the lacrimal precision required during laser welding as described above, and is a contributing factor to the occurrence of welding defects. Further, as shown in the side cross-sectional view of the ninth fixed part, a steel battery container 71 provided with a near-kel plating layer 71a is shown.
When a lid 72 similarly provided with a nickel plating layer 2a is fitted to the inner edge of the opening end of the lid 72 and welding is performed by irradiating a laser beam 76 from the upper surface of the joint surface, the welded portion 73 is heated as shown in the figure. There has been a problem in that minute racks 74 with a width of several tens of seventy-seven meters or less are likely to occur, which is thought to be due to such distortions.

As mentioned above, it is difficult to form a joint with a precision suitable for laser welding with the combination of a rectangular battery container and a lid using conventional technology, and when nickel-plated steel is used, the weld There is a problem that cracks tend to occur in the battery, resulting in insufficient sealing and reducing reliability as a sealed battery.

The present invention solves these problems, and uses steel plates with a thin nickel layer on the surface as the base plates for the battery container and lid, and provides a battery container formed by a molding method that combines ``shidoki'' processing. The purpose of this method is to improve the fitting accuracy of the joint between the battery container and the lid and to prevent the formation of fine cracks and racks in the welded portion.

Means for Solving the Problem In order to solve this problem, the present invention deep-draws a steel plate with a thin nickel layer on the surface of which the thickness is regulated to a predetermined thickness after forming. A notch step is formed on the inner edge of the opening end by ironing, and a steel plate with a thin nickel layer provided thereon, in the same way as the battery container, is molded onto the notch step of a rectangular battery container that is formed into a predetermined shape and size. A lid body with a planar peripheral edge is placed thereon, and the joint between the outer peripheral edge of the lid body and the opening edge of the battery container is sealed by laser welding.

Function: With this configuration, the lid body can be fitted to the opening edge of the battery container in a stable state with high precision, making laser welding easier, and the laser beam can locally and instantaneously weld the joint. By suppressing the strain caused by the presence of the nickel layer during melting and cooling, a crack-free weld is formed, resulting in a battery in a reliable sealed state.

Embodiment An embodiment of the prismatic sealed battery of the present invention will be explained with reference to the drawings.

FIG. 1 is a side cross-sectional view showing the main parts of the present invention of an example battery. FIG. 3 is a diagram showing a state in which the lid body 2 is being fitted and placed on the inner edge of the opening end of the battery container 1 of FIG. FIG. 2A shows the upper appearance of the example battery, and FIG. 2B shows a cross section of the main part of the side surface of A. The rectangular battery container 1 and lid body 2 and the thin nickel layer provided on their surfaces are the main components of the present invention, and the thin nickel layer is formed on the surface by matte electrolytic nickel plating or nickel cladding (described later). A rectangular battery container 1 is obtained by forming a rectangular container preformed using a deep drawing process using a provided steel plate, and shaping it into a predetermined size and shape by ironing, and forming a notch step 1e on the inner edge of the opening end; The battery container 1 has a shape that matches the inner edge of the stepped notch 1e as shown in the figure.
Lid body 2 with a flat peripheral edge formed by press punching (described later) from a steel plate provided with a thin nickel layer, similar to the battery container.
Use. The thickness of the thin nickel layers 1C and 2C on the inner edge of the raised portion of the notch step 1e of the molded battery container 1 and on the surface of the lid 2 (especially on the top side) is about 100%, as will be described later. It is preferable to regulate it to 2 to 10 ztm.

To describe an embodiment of a rectangular sealed alkaline storage battery to which the present invention is applied, as shown in FIG. A power generation element 3 injected and impregnated with a predetermined amount of alkaline electrolyte is inserted into a group of electrode plates in which a predetermined number of electrode plates and separators are stacked, and a negative electrode lead e is welded to the side wall. A positive terminal rivet 4a is fastened to the provided terminal hole 2a together with an insulating ring 4b and a metal washer 40 (if necessary, an explosion-proof function consisting of a cap and a rubber valve body can be added to the positive terminal rivet for use). (not shown>) The above-mentioned lid body 2 on which the positive electrode terminal 4 is formed,
(After connecting the positive electrode lead 5) Fit and place the battery container 1 on the cutout stepped portion 1e as shown in FIG. 7 is irradiated with a laser beam of 8 gold to form a weld 9 to seal the battery.

Next, the above-described battery container 1, lid 2, and the thin nickel layer provided on the surfaces thereof will be described.

As described above, a steel plate with a thin nickel layer provided on the surface is used as a molding material for the battery container 1 and the lid 2. The thin nickel layer can be provided as a low-hardness matte nickel plating layer by continuous electrolytic deposition on both sides of a coil material of a cold-rolled steel plate, for example, using a Watts bath with no brightening agent added, or
Alternatively, a nickel sheet formed by overlapping a nickel sheet on a steel plate coil similar to the above and forming a nickel cladding by cold roll bonding or explosion bonding is used.

FIGS. 3A, B, and C show the rectangular battery container 1 used in the present invention.
FIG. 3 is a schematic diagram showing a cross section of a main part of a side surface in a processing step.

4A, B, C, and D are schematic diagrams showing the dimensions and shape of the rectangular battery container 1 completed through the steps shown in FIG. 3. The thickness of the steel plate provided with the thin nickel layer used as a blank plate before molding is the same as or slightly thicker than the side wall thickness tl of the square container 1', and the side wall portion 1d of the completed battery container 1 in the fourth diagram is The thickness is approximately 1.16 to 1.6 times the thickness t, and the shape is sequentially formed into a cylindrical or elliptical shape using a commonly used deep drawing method, and expanded to the vicinity of the frontispiece as shown in Figure 3A. A square container 1' having a mouth portion 1ii is formed.

Next, the container 1' is adjusted to a predetermined size and shape using an ironing die shown in FIGS. 3B and 3C, and a notched stepped portion 1e is formed.

The ironing mold is a guide portion (nest) 22a.

It is mainly composed of an outer mold 22 having a die portion 22b, a punch 21 having a stepped portion 21a, and a receiving mold 23. The third guide portion 22a of the outer mold 22 fixed to the press machine
By placing the rectangular container 1' shown in Figure A and applying a pressing force in the direction of the arrow to the vertically movable punch 21, the rectangular container 1' is supported by the guide part 22a and die part 22b.
As shown in FIG. 3B, side wall portions 1c having predetermined dimensions and shapes are sequentially formed from the bottom as shown in FIG. 3B, and then as shown in FIG. By pushing it all the way down, a predetermined notch step 1 is formed, and the machining is completely completed. The rectangular battery container 1 thus formed was cut to a predetermined step height h to match the thickness of the lid shown in the fourth diagram (see Figure 1), and a thin nickel layer was applied to the surface. 1b, 1C,
A square (rectangular) battery container 1 is provided with a cutout stepped portion 1e.

In addition, in FIGS. 3B and 3C, the case where the ironing process is performed with one mold has been described, but a plurality of molds and a plurality of ironing processes may be provided depending on the ironing rate, the thickness type of the steel plate, etc. Further, the ironed battery container 1 is taken out from the outer mold 22 by a knockout bin 24 through the through hole of the receiving mold 23.

In the above, the inner dimensions Ld and W of the notch step portion 1e are
d, the notch width K shown in the fourth diagram is the side wall portion 1 of the battery container.
The thickness of d is set to about 20 to 50% of the thickness t. This ensures that the opening edge of the battery container 1 has the necessary thickness for laser welding.
It shows a range in which a normal-shaped cutout stepped portion 1e can be formed with high precision. The shape and dimensions of the lid body 2 are as follows:
The shape and dimensions match the internal dimensions Ld and Wd of the rising part of the die, and the press punching process applies precision drilling methods such as the fine blanking method and the new facing die method, resulting in good flatness of the punched periphery. If the external dimensions are 50w or less and the plate thickness is 1mm or less, an accuracy of 0.03wm can be obtained. When the lid body 2 is fitted and placed on the upper part of the stepped notch part 1e of the battery container 1 formed in this way as shown in FIG. 1, the gap 7a of the joint part 7 is o,oos~0.07m. However, we were able to improve the range to a point where it is well suited for laser welding.

As described above, the thin nickel layer provided on the surfaces of the battery container 1 and the lid 2 has at least the thickness 1C of the inner edge of the raised portion of the notch step 1e of the battery container 1 and the thickness of the lid 2.
The thickness of the portion of the upper surface periphery to be welded shall be 10 μm or less. In laser welding, this is melted by the spot of the laser beam and immediately cooled, so the welded part expands and contracts due to differences in physical properties such as the difference in thermal expansion coefficient between the steel material and the nickel layer, and due to strain in the nickel layer. This is to prevent fine cracks and racks from being easily generated in the welded part 73 as described in FIG. 9 as a conventional example due to tensile stress when the welded part is cooled and solidified. That is, it has been found that by suppressing the thickness of the nickel layer and not providing a nickel layer on the cut surface 1j of the battery container 1 and the cut surface 2d of the lid body 2, it is possible to significantly reduce the thermal strain caused during welding. It is. However, when the thickness of the nickel layer is 2 μm or more, there is no problem in weldability, but because the nickel concentration in the welded area 9 alloyed during melting is low, the welded area may This is undesirable because it causes rust and corrosion, which leads to a decrease in strength. Therefore, the guideline for setting the thickness of the thin nickel layer of the raw plate of the battery container 1 and lid body 2 before processing is as follows. If the periphery of the lid 2 shown in the figure is flat and the thickness does not change due to processing, the thickness (2C) of the thin nickel layer on at least the upper surface side of the lid 2 is 2 to 10 μm as described above. do. In areas where the thin nickel layer becomes proportionally thinner in areas that are expanded and become significantly thinner, such as the raised portions of the stepped notch 1e of the battery container 1, the thickness of the base plate is increased accordingly. A thin layer of nickel is provided. For example, if the thickness is 40% of the base plate, the thickness of the thin nickel layer should be set at 6 to 26 μm, so that the notch step 1e after molding can be
The thickness of the thin nickel layer 1C on the inner peripheral edge of the riser is 2 to 10
Regulate to ltm. Note that the thickness of the thin nickel layer on the outer surface of the battery container 1 should be increased to the extent that it does not affect the moldability when the thin nickel layer is outside the laser beam irradiation range, as in the case of the embodiment shown in FIG. You may. Furthermore, the thin nickel layer described above further reduces noise caused by thermal distortion during welding. Alternatively, in order to reduce the reflectance of the laser beam, it is desirable to use a matte material with low distortion, but in order to do so, care should be taken when nickel plating or when selecting a nickel sheet for the cladding material. ), weldability can be further stabilized by using a non-glossy material or applying annealing treatment before and after molding. In addition,
The above-mentioned cracks are likely to occur in the welded part during welding when a nickel layer is provided on the surface of the steel material. , alloy steel such as stainless steel, or single metal gold such as iron, when the same type of combination is used, the above-mentioned cracking phenomenon in the welded part will not be observed under normal laser welding conditions. .

With the above-described configuration, the shape of the battery container 1 is expressed as shown in FIG.
cm, kxo, 2m, hmo, 5+m, H=x4
rtm and matte electrolytic nickel plating (hardness Hv
1. A battery container molded from a blank plate with a thin nickel layer formed on a cold-rolled steel plate using the method (=-approximately 260). Using the lid 2, the rectangular sealed alkaline storage battery shown in FIG. 2 was welded and sealed using a YAG laser. In the above, a comparative product is one in which the thickness of each of the thin nickel layers 1C and 2C on the inner peripheral edge of the rising edge of the notch step 1e of the battery container 1 and the top surface of the lid body 2 is 12 to 1871 m. Conventional example A has the format shown in Figure 5B, with a nickel plating thickness of 3 to 1tm after molding.
A conventional example B with the same plating thickness of 10 to 191 trn was manufactured to the same size, and the number of defects was compared. The results are shown in Table 1.

Table 1 (Note) (Those with a → symbol indicate that the lid body is larger.

According to the present invention, as shown in Table 1, it can be seen that the failure rate during lid fitting and laser welding can be significantly reduced. In addition, due to the presence of the notched stepped portion 1e,
The laser output can be reduced without the laser beam penetrating into the battery, and the power generation element is not damaged.

Effects of the Invention As described above, according to the present invention, a battery container with a notch step formed using a steel plate with a thin nickel layer on the surface and ironing process is combined with a lid body with a flat peripheral edge. In particular, it is possible to improve the laminar precision of the joint, form a welded part that does not produce fine racks during laser welding, and improve long-term reliability and productivity.

[Brief explanation of the drawing]

1, 2, 3, and 4 show embodiments of the present invention, in which FIG. 1A is a cross-sectional view of the main part near the welding part of the rectangular sealed battery of the present invention, and FIG. FIG. 2A is a top external view of the rectangular sealed battery of the present invention, B is a side sectional view of A, and FIG. Processing process for the rectangular battery container of the present invention used in the batteries shown in Figures and Figure 2? A is a deep-drawn rectangular container, B is a state in the middle of ladder processing,
C is a diagram showing a state in which the laddering process has been completed and a notch stepped portion has been formed; FIG. 4 is a diagram showing a square battery container used in the present invention completed through the process of FIG. 3; A is a side view of one side; sectional view, B is a side sectional view of the other side, C is a top view, D is a sectional view showing the notch step at the upper side of the side, FIGS. 6, 6, 10, 11, 12, Fig. 13 is a cross-sectional side view showing the main parts of a conventional sealed battery, showing how the lid body and battery container fit together; Fig. 7 is a top view showing the molded shape of a conventional prismatic battery; Figs. 8 and 9. The figure is a sectional side view of a main part of a conventional battery showing a state during welding. 1... Square battery container, 1b, 1C...
・Nickel thin layer, 1e...Notch step, 2...
... Lid body, 2C ... Nickel thin layer, 3 ...
...Power generation element, 4...Positive terminal, 7...
...Joint part, 8...Laser beam, 9...
...Welded part, 1a, 2a... Steel material layer, 1
'...Square container, 1C...Side wall after ironing, 21...Punch, 21a...
... Stepped part of punch, 22 ... Outer mold, 22a ...
...Guide part, 22b...Dice part, 23
・・・・・・Reception mold. Name of agent: Patent attorney Toshi Nakao, and one other person [Q4 Nnochi1 OS F-I F-I
F”1 faction
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Claims (4)

[Claims] (1) A power generation element is placed in a rectangular battery container that is formed by deep drawing a steel plate with a thin nickel layer on its surface, forming a notch step on the inner edge of its open end by ironing, and molding it into a predetermined shape and size. stored on the notch step of the container,
A lid body with a flat peripheral edge made of a molded steel plate with a thin nickel layer similar to the battery container was placed, and the joint between the outer peripheral edge of the lid body and the opening edge of the battery container was sealed by laser welding. A prismatic sealed battery featuring: (2) The prismatic sealed battery according to claim 1, wherein the thin nickel layer of at least the welded portion of the molded battery container and lid has a thickness of about 2 to 10 μm. (3) A prismatic sealed battery according to claim 2, wherein the thin nickel layer is provided by electro-nickel plating. (4) The prismatic sealed battery according to claim 2, wherein the thin nickel layer is formed of nickel cladding.