WO2016043017A1 - Quadrangular cell case for vehicle cell and method for manufacturing same - Google Patents

Abstract

　The present invention is a quadrangular cell case 1 for a vehicle cell, wherein a bottom part 6, lateral walls 2, 3, 4, 5, and an opening part 7 are integrally formed from one sheet of an aluminum alloy plate into a case that has each of these parts and is rectangular in transverse cross-section; and, before a lid is seal-welded to the opening 7, upper portions 2c, 3c, 4c, 5c of the lateral walls 2, 3, 4, 5 to be welded are locally increased in thickness so as to protrude into the cell case. The quadrangular cell case 1 for a vehicle cell is made of aluminum alloy, and it is possible to form a bead configuration that has stabilized during seal-welding, and to form sound weld portions.

Description

Rectangular battery case for in-vehicle battery and manufacturing method thereof

The present invention relates to a prismatic battery case for an in-vehicle battery that is used in a state in which a large number of battery cases are arranged in parallel and incorporated in a module, and a method for manufacturing the same.

Conventionally, Li-ion batteries have been mainly used in the mobile field such as mobile phones and notebook PCs. However, in recent years, Li-ion batteries have been used for HV cars, plug-in hybrid cars, and electric cars for automobiles (in-vehicle use). ing.

Since these Li-ion batteries for automobiles require a large amount of power, a large number of battery cases are arranged in parallel in a limited in-vehicle space, and are incorporated and stored in a module. For this reason, it is important to avoid the excessive temperature rise because it is easy to parallel to each other, has a high space effect, has high mounting efficiency, has excellent heat dissipation performance.

For this reason, the battery case has a flat (cross-sectional) rectangular shape (square shape) and a large ratio of the width of the wide side surface to the width of the narrow side surface (the short side is significantly smaller than the long side). It is a battery case. A prismatic battery using such a thin prismatic battery case is suitable for reducing the thickness and weight of the device, and has a high space effect. Hereinafter, the Li-ion battery case for automobiles is also referred to as a rectangular battery case for in-vehicle batteries, a battery case for in-vehicle batteries, or simply a rectangular battery case or a battery case.

In such a rectangular battery case for an in-vehicle battery, internal organs such as a battery foil, an electrolytic solution, and a current collector are housed in an internal space, and then the opening is closed with a battery lid (hereinafter simply referred to as a lid). It is widely performed that the opening of the battery case and the joint of the battery lid are sealed and welded using laser welding.

Conventionally, in order to enhance the functionality of such a rectangular battery case, various examples have been proposed in which the thickness distribution of each part of the rectangular battery case is devised.

For example, in Patent Document 1, an iron metal outer can such as a cold rolled steel sheet of carbon steel is mainly proposed as a rectangular battery case for portable equipment such as a mobile phone. In this document, since the battery is used as a single battery, strength and rigidity are required even in a thin rectangular battery case. For this reason, the wall upper part thickness (opening part periphery side thickness) of the opening peripheral part sealed by a lid | cover is about 25% or less than the thickness of an intermediate part (steady part) in order to improve sealing strength. The metal outer can is made to be partially thick.

Japanese Patent Laid-Open No. 11-54095

Here, when the lid and body (can) of the rectangular battery case for in-vehicle batteries is made of a molded product obtained by integrally pressing an aluminum alloy plate (cold rolled plate) material from steel to aluminum alloy, corrosion resistance In addition, it is advantageous in terms of weight reduction, workability and cost. Therefore, studies have been promoted in recent years.
In addition, in order to further reduce the cost of a rectangular battery case for an in-vehicle battery made of an aluminum alloy, studies are being made to reduce the thickness. Specifically, there is a movement to reduce the thickness of the side wall of the battery case from about 0.5 to 1.0 mm to about 0.2 to 0.6 mm.

However, when the prismatic battery case for in-vehicle batteries is made of an aluminum alloy, if pursuing the above-mentioned thinning, the welding at the time of the sealing welding by the laser is not stable. Challenges arise.

That is, when the side wall of the rectangular battery case is made thin, in an aluminum alloy that is inferior in weldability than steel, thermal distortion of the plate occurs during sealing welding with the laser described above. Therefore, the welding with the lid made of the same aluminum alloy is not stable, the joint portion becomes corrugated, a step is generated, or the bead shape is unstable and penetrates the side wall of the welded portion. The contents of are badly affected. For this reason, in order to obtain a sound bead shape and a welded portion, a great deal of labor is required to reduce the efficiency during sealing welding, such as positioning the laser irradiation transfer with high accuracy.

Aluminum alloys have a low melting point and are likely to melt, but the specific heat and latent heat of fusion of aluminum alloys are larger than that of steel and most other metals, combined with good heat conduction, 5 times that of steel. Even heat is easy to escape. For this reason, local heating is difficult, and it is necessary to supply a larger amount of heat than steel in order to melt it. This is a major factor in that the above-described sealing welding is not stable and an unstable bead shape is formed.

The present invention has been made in view of such a problem, and is capable of stably performing the sealing welding, and enables a sound welded portion to be formed. An object is to provide a manufacturing method.

In order to achieve the above object, the gist of the in-vehicle battery square battery case of the present invention is integrally formed from a single material aluminum alloy plate into a case having a rectangular cross section having a bottom, a side wall, and an opening. In addition to being molded, the thickness of the side wall is reduced to a range of 0.2 to 0.6 mm, and the thickness of the bottom is increased to a thickness of 0.6 to 1.0 mm. Further, the thickness of the upper part of the side wall is partially thickened in advance so as to protrude toward the inside of the case.

In order to achieve the above object, the gist of the method for manufacturing a rectangular battery case for an in-vehicle battery according to the present invention is that a cross-sectional shape having a bottom portion, a side wall, and an opening portion is rectangular from a single material aluminum alloy plate. When the case is integrally formed, the thickness of the side wall is reduced to a range of 0.2 to 0.6 mm, and the thickness of the bottom portion is set to a range of 0.6 to 1.0 mm from the side wall. In addition, the thickness of the upper portion of the side wall is partially thickened in advance so as to protrude toward the inside of the rectangular battery case.

In the present invention, prior to sealing and welding an upper part of a side wall of a rectangular battery case made of a molded body of an aluminum alloy plate with an aluminum alloy lid and a laser, the thickness of the upper part of the side wall is changed to a steady part of the side wall. The thickness is partially increased toward the inner side of the rectangular battery case by an amount corresponding to the bead formation amount rather than the thickness of the battery.

Thereby, the sealing welding can be carried out stably, and a bead that does not penetrate the upper part of the side wall can be formed while extending over the upper part of the side wall and the lid, and a sound weld can be obtained.

It is a perspective view which shows one aspect | mode of this invention square battery case. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. It is sectional drawing which shows the one aspect | mode of the welding of the lid | cover of this invention square battery case. It is sectional drawing which shows the other aspect of welding of the lid | cover of this invention square battery case. It is sectional drawing which shows the one aspect | mode of the process of thickening the side wall of this invention square battery case. It is sectional drawing which shows the one aspect | mode of the welding of the lid | cover of the conventional square battery case. It is sectional drawing which shows the other aspect of the welding of the lid | cover of the conventional square battery case. It is sectional drawing which shows the other preferable aspect of the process of thickening the side wall of this invention square battery case.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

Basic structure of prismatic battery case:
1 to 3 show one embodiment of the rectangular battery case of the present invention. The rectangular battery case referred to in the present invention refers to an aluminum alloy battery case having a rectangular cross-sectional shape each having a bottom, a side wall, and an opening.

1 to 3, the rectangular battery case 1 is used as a vehicle battery as a premise. That is, a large number of battery cases 1 are arranged in parallel and used in a module. For this reason, in view of space efficiency, the battery case is made of a flat and thin aluminum alloy having a rectangular cross-sectional shape each having a bottom, a side wall, and an opening.

The rectangular battery case 1 basically includes a rectangular (rectangular in plan view) bottom 6, four side walls 2, 3, 4, 5 rising from each peripheral edge of the rectangular bottom 6, and the side walls 2, 3. 4 and 5 has a rectangular tube shape integrally having a rectangular opening 7 on the side of the upper ends 2a, 3a, 4a and 5a.

The rectangular shape referred to in the present invention includes a rectangular shape or a square shape, including the following description, or a shape that approximates a rectangular shape or a square shape, even if these shapes are not themselves.

In the rectangular battery case 1 of FIGS. 1 to 3, the side walls 4 and 5 are two opposite side walls on the long side as large and wide walls, and the side walls 2 and 3 are on the short side as small and narrow walls. Two opposing side walls. These side walls are rectangular in shape and have a large ratio between the width of the wide wall and the width of the narrow wall (the short side is significantly smaller than the long side), and are rectangular, flat and thin batteries. Construct a case.

The thickness (plate thickness) t6 of the rectangular bottom portion 6 is in the range of 0.6 to 1.0 mm, and the thickness (plate thickness) t2, t3 of the stationary portions 2b, 3b, 4b, 5b of the side walls 2, 3, 4, 5 t4 and t5 are selected from a range of 0.2 to 0.6 mm, and are made different from each other by the above-described forming of a plate having a uniform thickness. That is, it has a differential thickness square tube shape in which the thicknesses of these parts are different.

The thickness of the rectangular bottom 6 is made thicker than the respective side walls because of the necessity of strength (rigidity) of the battery case that is erected after being thinned. In addition, since a large number of battery cases 1 are closely arranged and assembled in a module and are in contact with the side walls of adjacent battery cases, the two side walls 4b on the long side, which may have relatively low strength, The thicknesses t4 and t5 of 5b may be thinner than the thicknesses t2 and t3 of the two side walls 2b and 3b on the short side. That is, the rectangular bottom portion 6 and the side walls 2 to 5 may be used for an in-vehicle battery, and the thickness may be changed by changing each thickness within the above range.

These rectangular battery cases 1 are made of a single material aluminum alloy plate (cold-rolled plate) having a uniform thickness (t1: 0.5 to 1.2 mm) as a drawing, ironing, etc. Can be integrally molded by a known multi-stage molding process. Incidentally, these multi-stage forming processes themselves include, for example, Japanese Patent No. 4119612, Japanese Patent No. 4325515, Plastic Work Process 2, W. Johnson, P.B. This is specifically described in the co-authored by Meller, published on October 30, 1965, Baifukan, “11.10 Redrawing of bottomed containers” on pages 26-27. The aluminum alloy plate used as the material of the rectangular battery case 1 is selected from alloys described later.

Installing the lid:
As shown in FIGS. 4 and 5, a rectangular lid 8 formed from a material aluminum alloy plate different from the rectangular battery case 1 is attached to the rectangular opening 7 of the rectangular battery case 1 in a plan view. Incidentally, the lid 8 may be produced by another manufacturing method such as casting, forging, and extrusion without necessarily forming a plate.

4 and 5 show a state in which the lid 8 is attached to the rectangular battery case 1 of FIG. 1, and only the AA cross section side of the rectangular battery case 1 is partially shown using the AA sectional view of FIG. Show. In the following description, there is also a description common to the BB cross section side in FIG. 1. In such a case, the reference sign on the BB cross section side is written in parentheses after the reference sign on the AA cross section side. Add to

The lid 8 has a rectangular shape (in plan view) that is the same as or similar to the rectangular shape in plan view of the upper part of the battery case. Usually, an external positive electrode, an electrolyte inlet, Other necessary parts such as a cover and a safety valve are provided. For this reason, the required strength (rigidity) is high, and the side walls 2, 3, 4, 5, or further thicker than the rectangular bottom 6, and the thickness (plate thickness) t 8 is 1.0. It is in the range of ~ 2.0 mm. The aluminum alloy plate used as the material of the lid 8 is also selected from the alloys described later.

As a mounting method generally used for mounting the lid 8, a typical lid method as shown in FIG. 4 is used. Specifically, the lid 8 is accommodated in a space surrounded by the upper ends 2a, 3a (4a, 5a) of the side walls, and the lid 8 and the upper ends 2a, 3a (4a, 5a) of the side walls are the same. There is a method of mounting on the same level of the plane. In addition, there is a method in which the lid 8 is placed on the upper end portions 2a, 3a (4a, 5a) of the respective side walls to cover the upper end portions of the respective side walls by the mounting method as shown in FIG.

When the lid 8 is mounted, the peripheral edge portions 8a and 8b of the lid 8 and the upper end portions 2a and 3a of the side walls or the upper portions 2c and 3c of the side walls are mutually connected from the welding direction indicated by the arrows in FIGS. Seal welding is performed by laser welding over the longitudinal direction or the periphery in plan view. However, only the upper end portions 2a and 3a or the upper portions 2c and 3c of the short side walls 2 and 3 are illustrated in FIGS.

FIG. 4 shows a laser beam from the upper side to the lower side toward the boundary (welded part) between the peripheral edge portions 8a and 8b of the lid 8 and the upper end portions 2a and 3a of the side walls, as indicated by a laser incident line X indicated by an arrow. FIG. 2 shows incident top-sealed sealing welding.
FIG. 5 shows that the laser is directed horizontally from the lateral direction toward the boundary (welded portion) between the peripheral edge portions 8a and 8b of the lid 8 and the upper end portions 2a and 3a of the side walls or the upper portions 2c and 3c of the side walls. As shown by a laser incident line X shown in FIG.
Although not shown in FIGS. 4 and 5, the upper ends 4a and 5a of the side walls 4 and 5 and the upper portions 4c and 5c in FIG.

Laser welding in sealing welding can be performed by using a well-known laser welding machine, such as a semiconductor excitation pulse transmission type YAG laser, a disk laser, or a fiber laser. . For example, continuous under conditions of laser output: 200 to 500 W, fiber diameter = 0.1 to 0.4 mm, welding speed = 10 to 20 m / min, shield gas = Ar (0.1 to 0.5 L / s), etc. Perform by welding.

Bead formation:
In this sealing welding, as shown in FIGS. 4 and 5, the upper portions 2c and 3c (4c and 5c) of the side walls and the peripheral portions 8a and 8b of the lid 8, for example, and the tip end portions 9a thereof It is necessary that a stable and healthy bead 9 is formed and joined so as not to penetrate the upper portions 2c and 3c (4c and 5c) of the side walls toward the inside of the battery case. This bead 9 extends in the longitudinal direction of the lid and the upper end of the side wall or the upper side of the side wall over the peripheral welds of the peripheral parts 8a and 8b of the lid 8 and the upper portions 2c and 3c (4c and 5c) of the side walls. It is formed over the periphery in plan view.

However, in the conventional example in which the side wall is thinned to a uniform thickness in the range of 0.2 to 0.6 mm, the side wall is too thin and sealing welding by laser is not stable. As described above, the specific heat and the latent heat of fusion of aluminum alloys are larger than those of steel and most other metals, and combined with good heat conduction, heat is likely to escape five times as much as steel. For this reason, as the side wall 21 which is a welded portion becomes thinner, local heating becomes more difficult, and it is necessary to supply a larger amount of heat than steel for melting, and sealing welding by laser becomes unstable.

Of course, depending on the laser welding conditions, the penetration depth H of the beads shown in FIGS. The thickness of these side walls is 80% or more. Therefore, as the thickness of the side wall 21 is reduced to the range of 0.2 to 0.6 mm, there is no room for the thickness of the side wall 21 with respect to the penetration depth H of the bead. Due to the characteristics of the aluminum alloy, depending on the welding conditions such as increasing the laser output, fiber diameter, peak output, and welding speed, the shape of the unstable bead 22 such that the tip 22a penetrates the upper portion 21a of the side wall. It is easy to become.

7 and 8 show a conventional welded portion of the thinned side wall 21 in which the upper portion 21a of the side wall also has a uniform thickness with the steady portion. As shown in FIGS. 7 and 8, if sealing welding by laser welding is not stable, the shape of the bead 22 that is unstable such that the tip 22a penetrates the upper portion 21a of the side wall tends to be obtained. This is the same for both the top-up method as shown in FIG. 7 and the side-weld type seal welding as shown in FIG.
Thus, when it becomes the unstable bead shape which the front-end | tip 22a penetrates, while joining strength falls, a spatter flies inside a battery case and a big damage and damage to the contents of a battery case are carried out. give.
For this reason, in order to make it a healthy bead shape and a welding part, extra labor and cost are required at the time of sealing welding. More specifically, in the past, in order to obtain a sound bead shape and welded part, the welding process was subdivided into multiple stages by reducing the welding current and welding speed at the expense of welding efficiency. Or more expensive welders with high control accuracy were required.

Thickening the side wall:
On the other hand, in order to form the above-described stable and healthy bead 9, in the present invention, the upper portions of the side walls 2, 3, 4, and 5 that are sealed and welded to the lid 8 are shown in FIGS. As shown in 2c, 3c, 4c, and 5c, partially than the thickness of the steady portions 2b, 3b, 4b, and 5b of the side walls so as to be thicker than the penetration depth H of the beads formed by the sealing welding. The thickness is increased in advance prior to the sealing welding.
Each of the upper portions 2c, 3c, 4c, and 5c of each side wall is partially thickened in advance so as to protrude only toward the inside of the rectangular battery case 1 or to swell as shown in FIGS. ing. Therefore, the outer walls of the upper portions 2c, 3c, 4c, and 5c of the side walls are preferably made thicker as in the outer walls of the stationary portions 2b, 3b, 4b, and 5b of the side walls as shown in FIGS. It is a flat wall without bulges or irregularities. Furthermore, the outer wall of each upper part 2c, 3c, 4c, 5c of each side wall is connected in the same plane as the outer wall of each said stationary part, and comprises the flat outer wall surface of the square battery case 1, respectively.

Here, as shown in FIGS. 4 and 5, the penetration depth H of the bead is from the outer surface portion 9 b of the bead 9 on the extension line of the laser incident line X indicated by the arrow, regardless of the laser incident direction. The maximum bead depth (maximum penetration depth) up to the tip 9a.

The thickness (plate thickness) of the steady portions 2b, 3b, 4b, and 5b of each side wall: t2, t3, t4, and t5 are selected from the range of 0.2 to 0.6 mm as described above. On the other hand, the thickness (plate thickness) of the upper portions 2c, 3c, 4c, and 5c of the side walls: t2c, t3c, t4c, and t5c are made thicker than the thicknesses t2, t3, t4, and t5 of these stationary portions. As a guideline, the thickness should be partially increased by an amount corresponding to the amount of bead 9 formed so as to be thicker than the penetration depth H of each bead at the upper portions 2c, 3c, 4c and 5c of the side walls. Is preferred.
Moreover, this thickening is partially thickened so as to project only toward the inner side (inner space) of the rectangular battery case 1. The square battery case of the present invention of FIG. 1 has thickened portions 2c and 3c in the AA cross-sectional view of FIG. 2, and thickened portions 4c and 5c in the BB cross-sectional view of FIG.

Such a thickening enables stable laser welding. 4 and 5, as shown on the right side of the side walls, the upper portions 2c and 3c (4c and 5c) of the side wall and the peripheral edge portions 8a and 8b of the lid, and the front end portion 9a thereof are the upper portion 2c of the side wall, A stable and healthy bead 9 that does not penetrate 3c (4c, 5c) is formed.
Further, by increasing the thickness of the upper portions 2c, 3c (4c, 5c) of the side wall, the penetration depth H of the bead 9 (or the allowable size of the bead 9) allowed in a range not penetrating the upper portion of the side wall is The effect of greatly increasing from the reduced thickness of the original side wall to the increased thickness is also great.
Further, by selectively thickening the upper portions 2c, 3c, 4c, and 5c of the side walls 2, 3, 4, and 5 to a depth equal to or greater than the penetration depth H of the bead 9, the selection range and allowable range of welding conditions are increased. And the stable welding becomes possible, and there is an effect that a stable and healthy bead 9 is formed.
That is, the effect that the bead 9 does not penetrate the upper part of the side wall, relaxes the allowable range of the sealing welding condition, and stabilizes the welding condition is great. The present invention makes it possible to perform stable laser welding on the premise of the basic structure of the rectangular battery case (including the thickness range of the lid 8, the rectangular bottom 6 and the side wall).

Furthermore, each upper part 2c, 3c, 4c, 5c of each side wall is partially thickened in advance so as to protrude only toward the inside of the rectangular battery case 1 or to swell. For this reason, the outer wall surface of each of the side wall upper portions 2c, 3c, 4c, 5c is flat without the bulge and unevenness due to the thickening as the outer wall surfaces of the stationary portions 2b, 3b, 4b, 5b of the respective side walls. It is a wall surface. That is, the outer wall surfaces of these side walls are flattened on the same plane (the same plane) including the upper portions 2c, 3c, 4c, and 5c of the thickened side walls.
As a result, it is connected in the same plane as the outer wall surface of the stationary part of each side wall, and each flat outer wall surface of the rectangular battery case 1 can be configured. Therefore, as a Li-ion battery for automobiles, even in a limited on-vehicle space, a large number of battery cases (outer walls) can be easily placed in parallel with each other, and the space effect is high.
Although flattening in the same plane with the outer wall surfaces of the stationary portions 2b, 3b, 4b, and 5b of the side walls of the outer wall surfaces of the respective side wall upper portions 2c, 3c, 4c, and 5c is not essential, It has the excellent space effect described above.

Here, in order to withstand the sound use as a battery case, a sufficient joint strength is required for the sealed welded portion. The joint strength depends on the penetration depth H of the bead 9. Of course, depending on the laser welding conditions, the bead penetration depth H is within the range of the side walls 2, 3, 4, 5 in order to ensure sufficient joint strength within the range of sealing welding conditions by lasers that are generally used. It is preferable that the thickness is 60% or more, preferably 80% or more of the thickness of these side walls with respect to the thickness t2, t3, t4, t5 of the stationary part.
However, when the thicknesses t2, t3, t4, and t5 of the stationary portions of the side walls 2, 3, 4, and 5 are as thin as 0.2 to 0.6 mm, the above-described thermal strain occurs during welding. Therefore, the melting becomes unstable, and the bead penetrates through the side wall in part.
In order to solve these problems, it is necessary to partially increase the thickness of the laser-welded welded part to suppress thermal distortion. And the problem of such welding is a problem peculiar to the aluminum alloy plate which requires a larger amount of heat input than the case of the steel plate like the said patent document 1. FIG.

For this reason, the thickness (plate) of the upper portions 2c, 3c, 4c, and 5c of each side wall is used as a guide for thickening the upper thick portions 2c, 3c, 4c, and 5c of the side walls with respect to the penetration depth H of the beads. Thickness): t2c, t3c, t4c, and t5c are partially thickened by 30% or more, more preferably 40% or more of the thicknesses t2, t3, t4, and t5 of the steady portions of the side walls 2, 3, 4, and 5, respectively. It is preferable that
When the thicknesses of the steady portions 2b, 3b, 4b, and 5b of the side walls 2, 3, 4, and 5 are different from each other, the thicknesses of the steady portions of the side walls to be thickened (the side walls to be thickened) are used as references. And
The upper limit of this thickening is about 70% from the design limit of internal volume and the processing limit of thickening. That is, the preferable range for increasing the thickness is 130 to 170%, more preferably 140 to 170% of the thickness of the side wall steady portion.

When the thickness of the side wall upper portions 2c, 3c, 4c, and 5c is less than 30% of the thickness t2, t3, t4, and t5 of the stationary portions of the side walls 2, 3, 4, and 5, the side walls 2, 3, 4, 5 In the case of an aluminum alloy plate having a thickness of 0.2 to 0.6 mm, thermal distortion occurs under the laser welding conditions, and the penetration and bead depth become unstable. For this reason, even if the welding conditions such as increasing the laser output, fiber diameter, peak output, and welding speed are corrected, the instability shown in FIGS. 7 and 8 such that the tip 22a penetrates the upper portion 21a of the side wall. The shape of the large bead 22 is likely to be obtained.

Incidentally, in the said patent document 1, as an iron square battery case, in order to raise intensity | strength (rigidity) as above-mentioned, the side thickness (sealing part periphery side thickness) of the upper opening periphery part sealed by a lid | cover is mentioned. In addition, the thickness is about 25% or less than the side thickness of the intermediate portion.
As in Patent Document 1, when only the strength and rigidity of the rectangular battery case are increased without recognizing the problem of sealing welding according to the present invention, the rigidity increases in proportion to the cube of the plate thickness. Therefore, if the plate thickness is increased by 10%, the rigidity can be increased by 30% or more.
Therefore, for Patent Document 1, it is not necessary to increase the thickness of 30% or more as in the present invention, and the purpose is to reduce the thickness as much as possible, which is about 25% or less, which is also the description range thereof. However, it also leads to not obstructing a certain weight reduction.

However, as in the present invention, in order to form a sound bead 9 in which the tip end portion 9a does not penetrate the upper part of each side wall, it is necessary to prevent thermal strain during welding. Considering the original thinning of 3, 4, 5 as well, it is necessary to increase the thickness.

The extension length (region) of the upper portions 2c, 3c, 4c, and 5c of each side wall that is thickened is a range where at least a bead extends (forms) under the battery case and the preconditions for welding, It is preferable that the range of the heat affected zone of welding be covered.

Furthermore, the increase in thickness of the upper portions 2c, 3c, 4c, and 5c of the respective side walls leads to the unevenness of the wall surfaces, which hinders the smoothing and flattening of the wall surfaces. To avoid. That is, the outer wall surfaces (side walls) of the prismatic battery case 1 are not thickened partially toward the inner side (inner space) of the prismatic battery case 1 and thickened toward the outer side of the prismatic battery case 1. The outer surface) keeps smoothing and planarization.

The thickening may be performed over the entire length and the entire width of each of the upper portions 2c, 3c, 4c, and 5c of the side walls where the beads 9 are formed by sealing and welding. Only the upper part of the side wall where the bead 9 is formed by welding may be selectively performed. However, the upper part and the upper end part of each side wall that is not sealed and welded may be thickened in view of the ease of thickening processing described later.

Thickening the upper side wall:
Such thickening of the side wall can be achieved by, for example, compressing the side wall as shown in FIG. The compression process itself shown in FIG. 6 is known and shows an aspect in which the upper portion 3c of the side wall 3 is thickened toward the inside of the battery case.
In FIG. 6, the cam structure 10 is sandwiched between the mold 3 from the outside of the side wall 3 and the core 11 from the inside of the side wall 3 with the core 11 around the upper part 3 c of the original uniform thickness. Thus, the upper portion 3c of the side wall 3 is compressed from above and partially thickened toward the inner side (inner space) of the rectangular battery case 1. This compression processing is performed in a plurality of stages depending on the degree of thickening.
By such processing, as shown in FIGS. 1 to 3, the upper portions 2c, 3c, 4c, and 5c of the respective side walls are partially thickened in advance so as to expand only toward the inside of the rectangular battery case 1. . As a result, the outer wall surface of each of the side wall upper portions 2c, 3c, 4c, and 5c is the same plane (the same surface) as the outer wall surface of the stationary portions 2b, 3b, 4b, and 5b of each side wall. It is possible to make a flat wall surface with no unevenness.

Preferred processing method for thickening the upper side wall:
As a processing method for increasing the thickness of each of the side wall upper portions 2c, 3c, 4c, and 5c, a processing method that is preferable to the compression processing of FIG. 6 is shown in FIGS. Show.

The outline of this processing method is that each side wall upper portion 2c, 2c, 3c, 4c, 5c is thickened partially in advance toward the inside of the rectangular battery case 1 in advance. The thickness is reduced by applying ironing to the side wall portions other than the upper portions of 3c, 4c, and 5c. On the other hand, the ironing process is not applied to the upper part of each of the side walls, and the original side wall thickness is left as it is as a thick part projecting toward the outside of the rectangular battery case 1.
Then, further processing is performed on the thick part on the upper side of the side walls 2, 3, 4, and 5, and the protruding direction of the thick part is reversed so as to be directed toward the inside of the rectangular battery case 1. Furthermore, the outer wall surface of the thick portion at the upper part of the side walls 2, 3, 4, 5 is formed into a flat surface that is the same plane as the outer wall surface of the other side wall portion that has been ironed.

9 will be described below. FIG. 9 shows a battery case before thickening as shown in FIG. 9 (a), that is, an intermediate molding in which the cross-sectional shape is substantially rectangular. Only the long side walls 4 and 5, the rectangular bottom 6, and the rectangular opening 7 in the BB cross section of FIG. 1 are shown as products.
Therefore, although the following description of the processing method is performed only for the long side walls 4 and 5, the same processing is performed for the short side walls 2 and 3, and all the side walls of the square battery case 1 The side wall upper thick parts 2c, 3c, 4c and 5c are formed into the same shape and structure.

FIG. 9B shows the cooperation of the ironing dies 13 and 13 from the outside of the side walls 4 and 5 and the punch 14 inserted from the opening 7 into the internal space of the battery case 1a (hereinafter simply referred to as the case). Thus, a mode of the first step is shown in which ironing is sequentially performed on the side wall portions 4b and 5b other than the upper portions 4e and 5e of the side walls 4 and 5.
In this first step, the side walls 4b and 5b other than the side wall upper portions 4e and 5e are thinned by the ironing process. Therefore, only the portions of the side wall upper portions 4e and 5e are not subjected to the ironing process, and are left as the respective plate thicknesses (wall thicknesses) of the original side walls 4 and 5, and the portions of the other side walls 4b and 5b subjected to the ironing process. As compared with the case, it is partially thickened into a shape having a convex portion protruding toward the outside of the case.

9 (c), (d) and (e) show the outer side of the case so that the protruding direction of the thickening (thick part) of the side wall upper parts 4e and 5e is directed toward the inside of the case. The aspect of the 2nd process reversed from the overhang direction which faces is shown.
In FIG. 9C, first, the punch 15 is inserted into the case from the opening 7.

Next, as shown in FIG. 9 (d), the punch 15 inserted into the case is lowered, and the narrow space provided on the lowermost side of the inner space (inner wall surface) of the annular sleeve 16 disposed around the lower portion of the punch 15. The rod-shaped tip 15b is inserted into the hole 16c.
A funnel-shaped (downwardly decreasing) taper portion 16b formed on the inner wall surface of the annular sleeve 16 above the pore 16c is formed in a funnel-shaped (lower side) above the tip portion 15b of the punch 15. The tapered sleeve 15a is pressed to expand the diameter of the annular sleeve 16 (taper 16b) in the left-right direction.

At the same time, as shown in FIG. 9 (d), the ironing dies 18 and 18 are pressed from the outside against the wall surfaces of the thickened side wall upper portions 4e and 5e ( thick wall portions 4e and 5e at the upper side walls). And on the other hand, the flat surface extended in the perpendicular direction of the annular outer peripheral part 17 provided above the punch 15 is made to contact | abut to the upper part of the inner wall surface of thick part 4e, 5e of a side wall upper part. Further, a taper portion 16a that is provided on the outer periphery of the upper portion of the annular sleeve 16 and expands downward is brought into contact with the lower portion inside the thick portions 4e and 5e at the upper portion of the side wall.

Then, the pressing dies 18 and 18 are pressed against the wall surfaces of the thick wall portions 4e and 5e at the upper side of the side wall, and the resulting side wall of the flat surface of the annular outer peripheral portion 17 and the tapered portion 16a at the upper portion of the annular sleeve 16 are accompanied. The upper thick parts 4e and 5e are pressed.
By these actions, the direction of thickening the thick portions 4e and 5e on the upper side wall is reversed (recessed) so as to project from the outer side of the case toward the inner side of the case. It is formed into thick parts 4c and 5c at the upper part of the side wall, which is a shape having a convex part projecting outward.
At the same time, the outer wall surfaces of the thick wall portions 4e, 5e (4c, 5c) at the upper side of the side wall are also flush with the outer wall surfaces of the other side walls 4b, 5b that have been ironed in FIG. 9 (b). ) Which is a flat wall surface extending in the vertical direction.
At the same time, the upper side of the thick wall portions 4e, 5e (4c, 5c) at the upper side of the side wall is formed into a flat wall surface extending in the vertical direction by the flat surface of the annular outer peripheral portion 17, while The lower side of the thick wall portions 4e, 5e (4c, 5c) on the upper side wall is formed into an inner wall taper portion 4d that expands downward.
Here, as the ironing dies 18, 18, the ironing dies 13, 13 used for ironing in FIG. 9B may be used, or another ironing die may be used.

After the second ironing process, the thickened part inside the case is deformed by controlling with a cam mechanism so that the side surface of the punch 15 is flat (the outer diameter in the longitudinal direction is uniform). Without letting go, the punch can be removed.
FIG. 9 (e) shows a mode in which the punch 15 is taken out from the opening 7 by the cam mechanism after the formation of the thick portions 4e and 5e at the upper side wall described above.
That is, contrary to FIG. 9 (d), the punch 15 inserted into the case is raised, and the tip portion 15 b is extracted from the hole 16 c of the annular sleeve 16 disposed below the punch 15. Then, by pressing the funnel-shaped taper portion 15a of the punch 15, the taper portion 16b of the annular sleeve 16 is released, and the diameter of the annular sleeve 16 is reduced, so that the punch 15 can be easily removed from the case.
The above-described series of processing methods in FIG. 9 can be applied to the processing of the thick portions of the other side wall upper portions 2c and 3c as they are.

In the processing method of FIG. 9, the side wall portions 4b and 5b other than the upper portions 4e and 5e of the side walls 4 and 5 are subjected to ironing to reduce the plate thickness, and the side wall upper portions 4e and 5e ( thick portions 4c and 5c). ), The plate thickness (wall thickness) of the original side walls 4 and 5 is left as it is without adding the ironing process.
Such a process of thickening only the upper portion of the side wall partially outside the case can be easily performed, and unlike the compression process of FIG. 6, it is not necessary to apply a large compressive force to the side wall, so that the side wall can buckle. There is an advantage that partial thickness can be efficiently increased.
Moreover, since the strength of the side wall portion thinned by the ironing process is increased by work hardening, the strength of the side wall portion is hardly reduced due to the reduction of the plate thickness.
Alternatively, even if the side wall portion is thinned by controlling the degree of work hardening by selecting the aluminum alloy composition and the ironing amount, it is possible to increase the strength.
These advantages are the same in the processing of the thick portions of the other side wall upper portions 2c and 3c.

Next, the thickened portions 4e and 5e at the upper side of the side wall once formed are reversed (recessed) from the outer side of the case so as to be directed toward the inner side of the case. It is easy to process.
At the same time, the outer wall surfaces of the side wall upper thick portions 4e and 5e are flattened in the same plane as the outer wall surfaces of the other side walls 4b and 5b that have been ironed in FIG. 9B. Easy.
These advantages are the same in the processing of the thick portions of the other side wall upper portions 2c and 3c.

Furthermore, the series of processing steps shown in FIG. 9 can be performed by one-step or multi-step continuous processing consisting only of the vertical movement of each punch to be used and each die. For this reason, it can be easily incorporated into a transfer press used for normal battery case molding, and has an advantage of being highly efficient and inexpensive.

The battery case 1a obtained in the processing step of FIG. 9 also has a thickness of the upper portions 2c, 3c, 4c, and 5c of the side wall of the rectangular battery case made of an aluminum alloy plate formed body, which is larger than the thickness of the steady portion of the side wall. The thickness can be partially increased toward the inside of the rectangular battery case by an amount corresponding to the amount of beads formed.

Thus, when the aluminum alloy lid 8 (not shown in FIG. 9) is sealed and welded by a laser, this sealing welding can be stably performed, and the beads 9 shown in FIGS. 4 and 5 can be formed. Can be a sound weld.
That is, as shown in FIGS. 4 and 5, the bead 9 extends over the side walls 2c, 3c, 4c and 5c and the lid 8 and does not penetrate the side walls 2c, 3c, 4c and 5c. Can be formed.
These effects can be realized by reducing the thickness of the portions other than the thick portions of the upper portions 2c, 3c, 4c, and 5c of the side walls, saving the material to be used, and reducing the material cost.

Material aluminum alloy plate:
The material aluminum alloy plate is selected from required characteristics as a material for a rectangular battery case, such as required strength, formability, corrosion resistance, creep resistance (creep deformation resistance), and sealing weldability.
In this respect, 1000 series or 3000 series aluminum alloy sheets specified in JIS or AA, which have mechanical properties at room temperature, 0.2% proof stress of 30 to 200 MPa, and total elongation of 3 to 20%. It is preferable that Among them, A3003 aluminum alloy is preferable, 1000 series aluminum alloy standardized by JIS or AA, and when sealing by laser welding, A1050 alloy which is a pure aluminum alloy is preferable.

These aluminum alloy plates have the above-mentioned properties by subjecting cold-rolled plates of uniform thickness to solution treatment and quenching treatment, age hardening treatment or annealing treatment as necessary. However, depending on the use conditions and the molding conditions, an alloy in which the creep resistance (creep deformation resistance) of these alloys is further improved, or a 2000 series or higher strength 5000 series or 6000 series aluminum alloy may be used. .

As described above, the present invention can provide a prismatic battery case for an in-vehicle battery made of aluminum alloy that can form a stable bead shape during the sealing welding and can form a sound welded portion, and a method for manufacturing the same. For this reason, it can be used suitably for the vehicle-mounted square battery case and its manufacturing method.

1: Battery case 2, 3, 4, 5: Side wall, 2a, 3a, 4a, 5a: Side wall upper end part, 2b, 3b, 4b, 5b: Side wall steady part, 2c, 3c, 4c, 5c: Side wall upper part ( (Thick part), 6: rectangular bottom, 7: rectangular opening, 8: lid, 9: bead, 9a: bead tip, 9b: bead outer surface, 10: cam structure, 11: core, 12: mold, 14, 15: punch, 13, 18: ironing die, 16: annular sleeve, 17: annular outer periphery, H: bead penetration depth, X: laser incident line

Claims (8)

1. A rectangular battery case for an in-vehicle battery, in which a cross-sectional shape having a bottom, a side wall, and an opening is integrally formed from a single material aluminum alloy plate into a rectangular case, and the thickness of the side wall is 0 The thickness of the bottom portion is 0.6 to 1.0 mm and the wall thickness is larger than that of the side wall. A rectangular battery case for an in-vehicle battery, wherein the thickness is partially thickened in advance so as to protrude toward the inside of the case.
2. The rectangular battery case for in-vehicle batteries according to claim 1, wherein the thickness of the upper part of the side wall is partially thickened in advance by 30% or more of the thickness of the steady part of the side wall.
3. The rectangular battery case for in-vehicle battery according to claim 1 or 2, wherein the outer wall surface of the side wall is flattened on the same plane including the upper part of the thickened side wall.
4. A method for manufacturing a rectangular battery case for an in-vehicle battery, wherein when a case having a rectangular cross-sectional shape each having a bottom, a side wall, and an opening is integrally formed from a single material aluminum alloy plate, the side wall The thickness of the bottom portion is reduced to a range of 0.2 to 0.6 mm, the thickness of the bottom portion is increased to a range of 0.6 to 1.0 mm, and the thickness of the bottom portion is increased. A method for manufacturing a rectangular battery case for an in-vehicle battery, wherein the thickness is partially thickened in advance so as to protrude toward the inside of the case.
5. The method for manufacturing a rectangular battery case for an in-vehicle battery according to claim 4, wherein the thickness of the upper part of the side wall is partially thickened in advance by 30% or more of the thickness of the stationary part of the side wall.
6. When the thickness of the upper part of the side wall is partially thickened in advance toward the inside of the case, the thickness is reduced by applying a squeezing process to a part other than the upper part of the side wall, while the upper part of the side wall Does not apply the ironing process, has the original side wall thickness and leaves it as a thick wall part that projects toward the outside of the case, and further processes the thick wall part at the top of the side wall. In addition, the method of manufacturing a rectangular battery case for an in-vehicle battery according to claim 4 or 5, wherein the protruding direction of the thick part is reversed so as to be directed toward the inside of the case.
7. 6. The vehicle-mounted battery according to claim 4, wherein, during the ironing process, the outer wall surface of the thick portion at the upper part of the side wall is flattened in the same plane as the outer wall surface of the other side wall part subjected to the ironing process. Manufacturing method for prismatic battery case.
8. The square for an in-vehicle battery according to claim 6, wherein, during the ironing process, the outer wall surface of the thick portion at the upper part of the side wall is flattened in the same plane as the outer wall surface of the other side wall part subjected to the ironing process. A battery case manufacturing method.

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