JP5101906B2 - Battery case molding method and molding apparatus - Google Patents

Description

  The present invention relates to a molding method and a molding apparatus for a battery case such as a lithium ion secondary battery used as a power source for portable electronic devices such as notebook computers, video cameras, and mobile phones.

  In this specification and claims, the term “aluminum” is used to include aluminum and its alloys. Further, the term “film” is used to include a sheet.

  Battery cases (packages) such as lithium ion secondary batteries are manufactured by forming a film material for molding made of a laminate of an aluminum foil and a resin film into a predetermined square shape by deep drawing by press molding. .

  In such deep drawing by press molding, the film material for molding is sandwiched between a die which is a female die of a press molding die and a wrinkle holding member, and the die hole (concave cavity) of the die, The molding film material (molding material) with the pulling of the material into the die hole due to slippage at the sandwiching part by relatively intruding the male punch from the wrinkle holding member side with a certain clearance. Is generally formed three-dimensionally.

Therefore, the wrinkle pressing member suppresses deformation such as wrinkles on the outer periphery of the drawing due to compression / tensile stress applied to the molding material during molding, so that the surface pressure (to allow the molding material to slide on the die side) ( Conventionally, coil springs are elastically contacted at a plurality of locations of the wrinkle pressing member as the pressure applying means (Patent Documents 1 and 2).
Japanese Patent Application Laid-Open No. 11-151531 JP 2000-102824 A

  However, when the coil spring is used as the pressure applying means of the wrinkle holding member as in the above-described prior art, the degree of compression of the coil spring at the time of forming increases as the forming depth of the drawing process increases. Increases, the molding material is strongly clamped between the dies and is not easily drawn into the die hole, and the degree of stretch molding accompanied by the stretching of the material is increased.

  Therefore, in the deep drawing processing by the conventional press molding, especially when the molding film material made of the laminate material is a molding target, it becomes difficult to form deeply because the aluminum foil is easily broken by stretching the material. Since the coil springs are elastically contacted at a plurality of portions of the wrinkle pressing member of the press molding die, the wrinkle pressing pressure becomes uneven and may cause wrinkles. In addition, since coil springs that are standardized in terms of cost are used, it is difficult to obtain the optimum wrinkle holding pressure that matches the molding shape, and coil springs can be used according to the size and depth of the molding shape. There is a problem that it is necessary to replace the one with an appropriate strength, and that the replacement work takes a lot of time and effort.

  The present invention has been made in view of such a technical background, and in a deep drawing process by press molding using a molding film material having a specific laminated structure as a molding material, wrinkles by a wrinkle holding member of a press molding die. The pressing pressure can be adjusted appropriately according to the size, depth, etc. of the molded shape, deep processing can be easily performed, the application range of the molded shape can be expanded, and uniform pressure can be applied to the entire wrinkle pressing member, It is an object of the present invention to provide a battery case molding method and molding apparatus that can be molded with high dimensional accuracy without causing wrinkles.

  As a result of intensive studies to achieve the above object, the present inventor has found that the above-mentioned problems can be solved by using air pressure as the wrinkle holding pressure by the wrinkle holding member of the press mold. It came to. That is, the present invention provides the following means.

  [1] A molding film material including a resin film layer as an outer layer, a resin film layer as an inner layer, and an aluminum foil layer disposed between the two film layers is formed from a die, a punch, and a wrinkle holding member. A method for forming a battery case, wherein a wrinkle holding pressure of the wrinkle holding member is applied by air pressure when forming into a predetermined shape using a press molding die.

  [2] The method for forming a battery case according to item 1 above, wherein the wrinkle holding pressure is set in a range of 0.01 to 1.0 MPa.

  [3] The method for forming a battery case according to item 1 above, wherein the wrinkle holding pressure is set in a range of 0.2 to 0.5 MPa.

  [4] The molding film material includes a heat-resistant resin stretched film layer as an outer layer, a thermoplastic resin unstretched film layer as an inner layer, and an aluminum foil layer disposed between the two film layers. 4. The method for forming a battery case according to any one of items 1 to 3 above.

  [5] A molding film material including a resin film layer as an outer layer, a resin film layer as an inner layer, and an aluminum foil layer disposed between both film layers is formed from a die, a punch, and a wrinkle holding member. An apparatus for molding into a predetermined shape using a press molding die, wherein a pneumatic cylinder is used as a wrinkle holding pressure applying means for the wrinkle holding member, and a plurality of the wrinkle holding members are provided on the pneumatic cylinder. A battery case molding apparatus, which is supported through a support pin of a book.

  [6] The battery case forming apparatus according to [5], wherein the pressure receiving area of the pneumatic cylinder is 0.1 to 2.0 times the pressing area of the wrinkle pressing member.

  [7] The battery case forming apparatus according to [5] or [6], wherein the stroke of the pneumatic cylinder is 2 to 20 times the stroke of the wrinkle pressing member.

  In the battery case molding method according to the invention of [1], since air pressure is used for the wrinkle holding pressure of the wrinkle holding member of the press mold, the wrinkle holding pressure is easily adjusted to the optimum value according to the molding shape. This expands the range of application of the size and depth of the molded shape, and in particular enables deep molding and does not require replacement for changing the spring pressure like a coil spring, thus improving workability. Moreover, since uniform wrinkle holding pressure can be applied to the entire outer peripheral side of the narrowed portion, sharp molding can be performed with high dimensional accuracy without generating wrinkles. Moreover, since wrinkles do not occur, in addition to improving the material yield, when continuously forming using a wound long forming film material, a material saving effect by shortening the forming pitch can be expected.

  In the invention of [2], since the wrinkle pressing pressure of the wrinkle pressing member is set within a suitable specific range, deep molding can be performed without causing wrinkles or breakage.

  In the invention of [3], since the wrinkle pressing pressure is set in a more optimal specific range, deep molding without wrinkles can be performed more reliably.

  In the invention of [4], the outer layer of the molding film material is a heat-resistant resin stretched film layer, and the inner layer is a thermoplastic resin unstretched film layer. Excellent deep drawability can be obtained without particularly increasing the thickness.

  In the battery case molding apparatus according to the invention of [5], since the wrinkle pressing pressure of the wrinkle pressing member of the press mold is applied by the pneumatic cylinder, the wrinkle pressing pressure is easily adjusted to the optimum value according to the molding shape. In addition, since the wrinkle holding member is supported on the pneumatic cylinder via a plurality of support pins, the air pressure of the pneumatic cylinder can be evenly transmitted to a plurality of locations of the wrinkle holding member, and the holding posture of the wrinkle holding member is It is stable and good moldability is obtained.

  In the invention of [6], since the ratio between the pressing area of the wrinkle pressing member and the pressure receiving area of the pneumatic cylinder is in a specific range, the pneumatic cylinder ensures the operating capability as a pressure applying means of the wrinkle pressing member during molding. Demonstrate.

  In the invention of [7], since the ratio of the stroke of the wrinkle pressing member and the stroke of the pneumatic cylinder is within a specific range, stable moldability can be obtained.

  1 and 2 show a schematic configuration example of a battery case molding apparatus M according to the present invention. FIG. 1 is a longitudinal front view before the start of molding, and FIG. 2 is a longitudinal front view at the end of molding. FIG. 3 shows a cross-sectional view of a film material (battery material for battery case) S which is a molding material.

  In this molding apparatus M, a rectangular parallelepiped punch 1 is projected upward on a fixed mold 11 placed and fixed on a gantry 10, and disposed so as to be movable up and down just above the fixed mold 11. A pneumatic cylinder in which a movable die 12 holds a thick plate-like die 2 having a rectangular die hole 2a, and a piston rod 30 protrudes vertically upward at a position directly below the fixed die 11 under the frame 10. 3 is installed. A rectangular support plate 4 is fixed to the upper end of the piston rod 30 of the pneumatic cylinder 3 in a horizontal posture, and support pins 4 a erected vertically at the same height at four corners of the rectangular support plate 4. 10 and the fixed mold 11, and a thick plate-like wrinkle pressing member 5 disposed between the fixed mold 11 and the movable mold 12 is supported in a horizontal position at the top ends of the support pins 4 a. .

  The die hole 2a of the die 2 is set to a size larger than that of the punch 1 so as to generate a predetermined clearance required for drawing forming over the entire circumference between the die hole 2a and the punch 1 fitted inside during the forming. The wrinkle pressing member 5 constitutes a press mold together with the punch 1 and the die 2, and a rectangular hole 5a through which the punch 1 is inserted is formed at the center thereof. Thus, both the lower surface of the die 2 and the upper surface of the wrinkle holding member 5 form a smooth flat surface along the horizontal direction.

  The pneumatic cylinder 3 has upper and lower air supply / exhaust ports 31, 32. Air supply from the lower air supply / exhaust port 32 to the cylinder lower chamber 3 b side and an upper air supply / exhaust port 31 from the cylinder upper chamber 3 a side are provided. Due to the exhausted air, the internal piston 33 rises, and the wrinkle pressing member 5 rises integrally with this. Further, by blocking the air flow through both the air supply / exhaust ports 31, 32, an air cushion action based on the pressure receiving area of the piston 33 and the internal pressure on the cylinder lower chamber 3b side is exerted against the downward load applied to the piston rod 30. The

  When forming a battery case such as a lithium ion secondary battery, first, as shown in FIG. 1, a film material for forming (battery for battery case) is formed on the wrinkle holding member 5 with the die 2 in the raised position. ) Put S. At this time, the resin film layer 7 as an inner layer of the molding film material S is placed so as to contact the upper surface of the wrinkle pressing member 5. That is, the resin film layer 7 as the inner layer of the molding film material S is placed so as to face the top surface of the punch 1 (see FIGS. 1 and 3).

  Next, in a state in which the wrinkle pressing member 5 is pressurized by the operation of the pneumatic cylinder 3, the movable mold 12 is lowered to prevent the pressure between the die 2 and the wrinkle pressing member 5 while resisting the pressure of the pneumatic cylinder 3. The film material S for shaping | molding is clamped by.

  At this time, after the molding film material S comes into contact with the lower surface of the die 2, a predetermined amount of air is supplied from the lower air supply / exhaust port 32 of the pneumatic cylinder 3 to increase the internal pressure on the cylinder lower chamber 3b side. Since the wrinkle pressing pressure corresponding to the internal pressure is applied to the forming film material S via the wrinkle pressing member 5, the wrinkle pressing pressure can be arbitrarily set by adjusting the internal pressure.

  Next, the movable mold 12 is lowered to a predetermined position in a state where the air flow through both the air supply / exhaust ports 31 and 32 of the pneumatic cylinder 3 is shut off, and as shown in FIG. Is inserted into the die hole 2a of the die 2 while drawing the molding film material S in contact with the top surface, and the rectangular battery housing portion D is drawn into the molding film material S. Then, by returning the movable mold 12 to the raised position after the molding, a three-dimensional molded product as a battery case can be taken out.

  According to the battery case forming method using such a forming apparatus M, the wrinkle holding pressure by the wrinkle holding member 5 of the press mold can be easily adjusted to the optimum value according to the forming shape. The application range of the size and depth of the molded shape is expanded, and in particular, deep molding becomes possible. In addition, the air pressure by the single pneumatic cylinder 3 is applied to the entire outer peripheral side of the narrowed portion of the forming film material S through the four support pins 4 and the wrinkle holding member 5 as wrinkle holding pressure. Therefore, sharp molding can be performed with high dimensional accuracy without generating wrinkles. Further, in this molding apparatus M, it is not necessary to replace a member for changing the pressure as in the conventional configuration using a coil spring as a means for applying the wrinkle holding pressure, so that the workability is improved, and a highly efficient molding process is performed. It becomes possible.

  Furthermore, in this molding method, wrinkles of the molded product can be surely prevented by a moderate wrinkle holding pressure, so that the material yield is improved. In addition, when a long film wound as the forming film material S is used and continuous forming is performed by intermittent feeding, a material saving effect by shortening the forming pitch can be expected.

  Here, the wrinkle pressing pressure by the wrinkle pressing member 5 is preferably set in the range of 0.01 to 1.0 MPa. If the wrinkle holding pressure is less than 0.01 MPa, the molding film material S is squeezed into the die hole 2a by the punch 1 in a state where the pressing force is weak. There is a risk of wrinkling the part. Further, when the wrinkle holding pressure exceeds 1.0 MPa, the outer peripheral side of the narrowed portion of the forming film material S is substantially fixed between the die 2 and the wrinkle holding member 5, and the forming is performed by extending the material. It becomes difficult to perform deeper molding because the material tends to break in the form of bulging molding due to. Therefore, the most preferable wrinkle holding pressure is 0.2 to 0.5 MPa. In this pressure range, both drawing and stretch forming work appropriately, so that even when deeper forming is performed, forming without wrinkles Is possible.

  On the other hand, it is preferable to set the pressure receiving area to 0.1 to 2.0 times the pressing area of the wrinkle pressing member 5 in order to provide the pneumatic cylinder 3 with sufficient operating capability. If this pressure receiving area is smaller than 0.1 times the pressing area, the operating capability is weak, and therefore the pressing force of the wrinkle pressing member 5 is insufficient, which may cause wrinkles in the molded product. If the pressure receiving area exceeds 2.0 times the pressing area, there is no problem in molding, but the pneumatic cylinder 3 becomes large and uneconomical. The optimum pressure receiving area is about the same as the pressing area of the wrinkle pressing member 5.

  The stroke of the pneumatic cylinder 3 is preferably 2 to 20 times the stroke of the wrinkle holding member 5, that is, the molding drawing depth. If it is less than 2 times, stable moldability cannot be obtained. Conversely, if it exceeds 20 times, the effect is not changed, but a large installation space is required, which is uneconomical. The optimum stroke of the pneumatic cylinder 3 is 10 to 15 times the stroke of the wrinkle holding member 5.

  In addition, as a shaping | molding depth of a battery case, 4-10 mm is common.

  Although the illustrated forming apparatus M has a configuration in which the punch 1 side is fixed and the die 2 side is movable, conversely, a configuration in which the punch 1 side is movable and the die 2 side is fixed may be employed.

  As shown in FIG. 3, the molding film material S includes a resin film layer 6 as an outer layer, a resin film layer 7 as an inner layer, and an aluminum foil layer disposed between the two film layers 6 and 7. 8 and adhesive layers 9a and 9b interposed between these film layers.

  Therefore, the resin film layer 6 of the outer layer plays a role of ensuring good moldability, that is, a role of preventing breakage due to necking of the aluminum foil layer 8 at the time of molding, and has a thickness of 12 to 50 μm. In particular, it is recommended to use a stretched heat-resistant resin film.

  Specific examples of the heat resistant resin stretched film include a biaxially stretched polyamide film, a biaxially stretched polyethylene naphthalate (PEN) film, and a biaxially stretched polyethylene terephthalate (PET) film. If these biaxially stretched films are used, the moldability is further improved, and a sharper and deeper shape can be formed.

  The resin film layer 7 of the inner layer plays a role of imparting excellent chemical resistance and heat sealability to a highly corrosive electrolytic solution used in a lithium ion secondary battery or the like. It is recommended to use a stretched film.

  The thermoplastic resin unstretched film used for the resin film layer 7 is not particularly limited, but is selected from the group consisting of polyethylene, polypropylene, olefin copolymers, acid-modified products thereof, and ionomers. An unstretched film made of at least one kind of thermoplastic resin is preferred.

  Moreover, the thickness of the resin film layer 7 of such an inner layer is preferably in the range of 20 to 80 μm. When the thickness is 20 μm or more, pinholes can be sufficiently prevented from being generated, and by setting the thickness to 80 μm or less, the amount of resin used can be reduced, and the cost can be reduced. Especially, it is especially preferable that the thickness of the resin film layer 7 as the inner layer is set to 30 to 50 μm.

  The resin film layer 6 as the outer layer and the resin film layer 7 as the inner layer may both be a single layer or a multilayer.

  The aluminum foil layer 8 plays a role of imparting gas barrier properties to prevent the entry of oxygen and moisture into the battery case, and a foil having a thickness of 5 to 50 μm made of pure Al or an Al—Fe alloy is used. Preferably used.

  Although it does not specifically limit as the adhesive bond layer 9a interposed between the resin film layer 6 and the aluminum foil layer 8 of an outer layer, For example, a urethane type adhesive layer and an acrylic type adhesive layer are suitable, and especially sharp A urethane-based two-component reactive adhesive layer is recommended for molding.

  The adhesive layer 9b interposed between the resin film layer 7 as the inner layer and the aluminum foil layer 8 is not particularly limited. For example, other than acid-modified polyolefin such as maleic anhydride-modified polyethylene and maleic anhydride-modified polypropylene. And an adhesive layer formed of urethane resin, acrylic resin, thermoplastic elastomer-containing resin, or the like. Such an adhesive layer 9b is formed, for example, by laminating an adhesive resin film (for example, a heat-modified polyolefin film) on one side of the resin film layer 6 as an outer layer.

  The film material S for molding used as a molding material in the present invention is not necessarily provided with the adhesive layers 9a and 9b, and may be composed only of the inner and outer resin film layers 6 and 7 and the intermediate aluminum foil layer 8. It can be used.

  Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples. In addition, the structure of the film material S for shaping | molding and the press die used in the Example etc. is as follows.

[Film material for molding]
A maleic anhydride-modified polypropylene layer having a thickness of 3 μm and an unmodified polypropylene layer having a thickness of 12 μm are coextruded, and an aluminum foil (AA8079-) having a thickness of 40 μm is formed from one side of the coextruded product 9b. O material) 8 was supplied, and a polypropylene unstretched film 7 having a thickness of 30 μm was supplied from the other surface side, and these were sandwiched between a pair of heat and pressure rolls and heat laminated to obtain a laminated film. Next, after applying urethane resin adhesive 9a to the surface of aluminum foil 8 of the laminated film obtained with a gravure roll and drying it to some extent by heating, the adhesive surface is a biaxial shaft made of nylon having a thickness of 25 μm. The stretched film 6 was laminated to obtain a molding film material (battery material for battery case) S having the configuration shown in FIG.

[Press mold]
(Punch 1) ... 60 mm long side, 45 mm short side, corner R: 1.5 mm, punch shoulder R: 1.5 mm, surface roughness: mirror finish (Ra = 0.3 μm or less)
(Die 2)... Die hole 2a long side 60.5 mm, short side 45.5 mm, die shoulder R: 0.5 mm, surface roughness: mirror finish (Ra = 0.3 μm or less)
(Wrinkle holding member 5): 200 mm long, 150 mm wide, 20 mm thick, rectangular hole 5a: same dimensions as die hole 2a, surface roughness: mirror finish (Ra = 0.3 μm or less).

<Example 1>
In the molding apparatus M shown in FIGS. 1 and 2 equipped with a press molding die (molding height free) having the above-described configuration, the molding is made into a blank shape of 110 × 180 mm according to the apparatus specifications and molding conditions shown in Table 1. Using the film material S as a molding material, a battery case was prepared by performing a deep drawing one-step molding with a molding height of 5 mm and a deep drawing one-step molding with a molding height of 6 mm.

<Example 2>
A battery case was produced in the same manner as in Example 1 except that the wrinkle holding pressure was set to 0.5 MPa.

<Example 3>
A battery case was produced in the same manner as in Example 1 except that the wrinkle holding pressure was set to 0.1 MPa.

<Example 4>
A battery case was produced in the same manner as in Example 1 except that the wrinkle holding pressure was set to 1.0 MPa.

<Example 5>
A battery case was fabricated in the same manner as in Example 1 except that the ratio of the pressure receiving area of the pneumatic cylinder to the pressing area of the wrinkle pressing member was set to 0.08.

<Example 6>
A battery case was fabricated in the same manner as in Example 1, except that the ratio of the pressure receiving area of the pneumatic cylinder to the pressing area of the wrinkle pressing member was set to 2.5.

<Example 7>
A battery case was fabricated in the same manner as in Example 1 except that the ratio of the stroke of the pneumatic cylinder to the stroke of the wrinkle holding member was set to 1.5.

<Example 8>
A battery case was fabricated in the same manner as in Example 1 except that the ratio of the stroke of the pneumatic cylinder to the stroke of the wrinkle holding member was set to 22.

<Example 9>
A battery case was produced in the same manner as in Example 1 except that the wrinkle holding pressure was set to 1.5 MPa.

<Comparative Example 1>
A battery case was fabricated in the same manner as in Example 1 except that a conventional coil spring was used instead of the pneumatic cylinder as a means for applying pressure to the wrinkle holding member.

  The moldability of the molded product (battery case) obtained as described above and the presence or absence of wrinkles were evaluated based on the following evaluation methods.

<Formability evaluation method>
For each molding height (5 mm, 6 mm), the moldability in deep drawing was evaluated in four stages based on the following criteria. In other words, “◎” indicates that the molded product did not crack at all, including micro-cracks, and “○” indicates that the micro-crack may occur rarely but the molded product did not substantially crack. In addition, although a very small part of the cracks was generated, there was no problem in practical use. The evaluation results are shown in Table 1.

<Appearance evaluation method (evaluation of the presence or absence of wrinkles)>
For each molding height (5 mm, 6 mm), the appearance evaluation on the presence or absence of wrinkle generation in the molded product was evaluated based on the following criteria. That is, “◎” indicates that no wrinkle was observed, and “○” indicates that there was a slight minimum wrinkle that was difficult to visually confirm, but “○” indicates that it was not substantially visible. “△” indicates that a part of the wrinkles was recognized but had no practical problem, and “×” indicates that many wrinkles occurred. The evaluation results are shown in Table 1.

  As is apparent from Table 1, according to the molding methods and molding apparatuses of Examples 1 to 9 of the present invention, good moldability is obtained even in deep molding, and the obtained molded product has practical problems. It had a good appearance without.

  On the other hand, in the molding method and molding apparatus of Comparative Example 1 using the spring pressure of the coil spring as the wrinkle holding pressure, cracks occurred on almost the entire surface, and good moldability was not obtained.

It is a vertical front view before the shaping | molding start in one Embodiment of the shaping | molding apparatus of the battery case which concerns on this invention. It is a vertical front view at the time of completion | finish of shaping | molding of the shaping | molding apparatus. It is sectional drawing which shows one Embodiment of the film material for shaping | molding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Punch 2 ... Die 2a ... Die hole 3 ... Pneumatic cylinder 3a ... Cylinder upper chamber 3b ... Cylinder lower chamber 30 ... Piston rod 31 ... Upper air supply / exhaust port 32 ... Lower air supply / exhaust port 33 ... Piston 4 ... Rectangular support plate 4a ... Support pin 5 ... Wrinkle holding member 5a ... Rectangular hole 6 ... Resin film layer (outer layer)
7 ... Resin film layer (inner layer)
8 ... Aluminum foil layer D ... Battery housing part M ... Molding device S ... Film material for molding

Claims (5)

A molding film material comprising a resin film layer as an outer layer, a resin film layer as an inner layer, and an aluminum foil layer disposed between the two film layers, is formed by press molding comprising a die, a punch, and a wrinkle holding member. upon formed into a predetermined shape by using a mold, the blank holding pressure of the wrinkle pressing member by a pneumatic pneumatic cylinders set in the range of 0.01～1.0MPa, the air flow of the supply and exhaust port of a pneumatic cylinder A battery case forming method, wherein the battery case is formed in a closed state .   The method for forming a battery case according to claim 1, wherein the wrinkle holding pressure is set in a range of 0.2 to 0.5 MPa. The molding film material includes a heat-resistant resin stretched film layer as an outer layer, a thermoplastic resin unstretched film layer as an inner layer, and an aluminum foil layer disposed between the two film layers. 3. A method for forming a battery case according to 1 or 2 . A molding film material comprising a resin film layer as an outer layer, a resin film layer as an inner layer, and an aluminum foil layer disposed between the two film layers, is formed by press molding comprising a die, a punch, and a wrinkle holding member. An apparatus for forming a predetermined shape using a mold, wherein a pneumatic cylinder is used as a wrinkle holding pressure applying means for the wrinkle holding member, and the wrinkle holding member is supported by a plurality of the pneumatic cylinders. Ri Na is supported via a pin, shut off from the pressing area of the wrinkle pressing member, the pressure receiving area of the pneumatic cylinder is 0.1 to 2.0 times, the air flow of the supply and exhaust port of the pneumatic cylinder molding device of the battery case, characterized that you have been made shall be molded in a state. The battery case molding device according to claim 4 , wherein the stroke of the pneumatic cylinder is 2 to 20 times the stroke of the wrinkle holding member.

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