Square can manufacturing method and square can manufacturing device

Abstract

To provide a square can manufacturing method and a square can manufacturing device that suppress occurence of ununiformity in thickness of a long side wall without increasing cost of manufacture.SOLUTION: A square can manufacturing method includes a drawing and ironing process in which drawing and ironing are performed for a planned cylindrical part of an intermediate molded product. A die and a punch are formed so that in the state that the punch is inserted in a die processing open hole 41a in an unloaded condition, a short side direction interval W1 between a long side direction center part of a punch long side wall processing part 42b and a die long side wall processing part 41c becomes narrower than a short side direction interval W2 between long side direction both end parts of the punch long side wall processing part 42b and the die long side wall processing part 41c.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for manufacturing prismatic cans, and more particularly to a method and apparatus for manufacturing prismatic cans used as cases for lithium-ion batteries. [Background technology]

[0002] Conventionally, a known method for manufacturing a metal rectangular can having a bottom wall and a rectangular tubular portion involves performing multiple drawing or drawing and ironing processes on a blank to produce the rectangular can (see, for example, Patent Document 1). It is also known that in the drawing and ironing process, which is carried out as the final step of such drawing or drawing and ironing processes, a punch having a punched outer peripheral surface formed with a substantially rectangular cross-sectional shape and a die having a die-machined through-hole similarly formed with a substantially rectangular cross-sectional shape are used, taking into consideration the outer and inner dimensions of the rectangular tubular portion of the final formed product. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-51575 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the applicant has confirmed that in the case of rectangular cans formed in this manner, when the flattening ratio (the ratio of the long side dimension to the short side dimension) of the rectangular tubular portion of the rectangular can being manufactured is high, uneven thickness occurs in the long side wall of the rectangular tubular portion.

[0005] Depending on the application of the rectangular can, such as when it is used as a case for a lithium ion battery, which requires high shape precision, such unevenness in the wall thickness of the rectangular cylindrical portion may not be acceptable.

[0006] The present invention aims to solve these problems and provide a method and apparatus for manufacturing rectangular cans that has a simple configuration, prevents unevenness in the thickness of the long side walls, and does not increase manufacturing costs. [Means for solving the problem]

[0007] The method for manufacturing a prismatic can of the present invention is a method for manufacturing a prismatic can having a prismatic tubular portion having a bottom wall, a pair of long side walls, and a pair of short side walls, and the method includes a drawing and ironing step of drawing and ironing a portion to be a tubular portion of an intermediate formed product in a gap between a die-processed inner peripheral surface of a die-processed through hole formed in a die and a punch-processed outer peripheral surface formed on a punch inserted into the die-processed through hole, and the die-processed inner peripheral surface is a die long side wall processing portion that processes the portion to be the long side wall of the intermediate formed product. and a die short side wall processing section for processing a planned short side wall portion of the intermediate molded product. The punched outer peripheral surface has a punch long side wall processing portion for processing the intended long side wall portion. a punch short-side wall processing portion for processing the short-side wall planned portion; and a curved corner portion for smoothly connecting the punch long-side wall processing portion and the punch short-side wall processing portion. The die and punch are formed so that when the punch is inserted into the die machining through-hole in an unloaded state, the short-side distance between the long-side center of the punch long-side wall machining portion and the die long-side wall machining portion is narrower than the short-side distance between both long-side ends of the punch long-side wall machining portion and the die long-side wall machining portion, thereby solving the above problem. The present invention provides a prismatic can manufacturing apparatus for manufacturing a prismatic can having a prismatic tubular portion having a bottom wall, a pair of long side walls, and a pair of short side walls, the prismatic can manufacturing apparatus including a drawing and ironing unit that applies drawing and ironing to a portion to be the tubular portion of an intermediate formed product in a gap between a die-processed inner peripheral surface of a die-processed through hole formed in a die and a punch-processed outer peripheral surface formed on a punch inserted into the die-processed through hole, and the die-processed inner peripheral surface is provided with a die long side wall processing unit that processes the portion to be the long side wall of the intermediate formed product. and a die short side wall processing section for processing a planned short side wall portion of the intermediate molded product. The punched outer peripheral surface has a punch long side wall processing portion for processing the intended long side wall portion. a punch short-side wall processing portion for processing the short-side wall planned portion; and a curved corner portion for smoothly connecting the punch long-side wall processing portion and the punch short-side wall processing portion.The die and punch are formed so that when the punch is inserted into the die machining through-hole in an unloaded state, the short-side distance between the long-side center of the punch long-side wall machining portion and the die long-side wall machining portion is narrower than the short-side distance between both long-side ends of the punch long-side wall machining portion and the die long-side wall machining portion, thereby solving the above problem. [Effects of the Invention]

[0008] According to the present invention, by forming the die and punch so that, when the punch is inserted into the die-machined through-hole under no load, the short-side distance between the long-side center of the punch long-side wall processing portion and the die long-side wall processing portion is narrower than the short-side distance between both long-side ends of the punch long-side wall processing portion and the die long-side wall processing portion, it is possible to suppress unevenness (bias) in the thickness of the long-side wall of the molded rectangular can with a simple configuration and without increasing manufacturing costs. In other words, if the flattening ratio (the ratio of the long-side dimension to the short-side dimension) of the die-machined through hole is high, the molding reaction force may cause the die long-side wall processing portion to bend during the drawing and ironing process, such that the center of the long-side wall processing portion moves outward in the short-side direction.However, in the present invention, the short-side distance between the die long-side wall processing portion and the punch long-side wall processing portion is set in consideration of the bending of the die long-side wall processing portion.This makes it possible to reduce the dimensional difference between the short-side distance between the die long-side wall processing portion and the punch long-side wall processing portion at both long-side ends and the short-side distance between the die long-side wall processing portion and the punch long-side wall processing portion at the center in the long-side direction during the drawing and ironing process, when the die long-side wall processing portion is bent due to the molding reaction force.This makes it possible to make the thickness distribution of the long-side wall of the formed rectangular can more uniform. Furthermore, with the present invention, there is no need to take measures to suppress the deflection of the die long side wall processing portion itself, such as changing the die mold material to a material with a high Young's modulus, such as cemented carbide, which would increase manufacturing costs, and therefore increases in manufacturing costs can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is an explanatory diagram showing a rectangular can that is a final formed product of the rectangular can manufacturing method according to one embodiment of the present invention. [Figure 2] 1A to 1C are explanatory diagrams showing the steps of a method for manufacturing a rectangular can. [Figure 3] 1A to 1C are explanatory diagrams showing the steps of a method for manufacturing a rectangular can. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] 10A and 10B are explanatory views showing a state in which a punch is inserted into a die-machined through-hole of the drawing and ironing unit under no load, and a modified example. [Figure 7] FIG. 4 is an explanatory diagram showing the state of a die and a punch during drawing and ironing. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] FIG. 1 is an explanatory diagram illustrating the canning phenomenon. DETAILED DESCRIPTION OF THE INVENTION

[0010] A method for manufacturing a prismatic can and an apparatus 10 for manufacturing a prismatic can according to one embodiment of the present invention will be described below with reference to the drawings. [Square can 60 (final molded product)]

[0011] First, a square can 60, which is the final molded product produced by the square can manufacturing method and square can manufacturing apparatus 10, is made of a metal such as aluminum, and in this embodiment is used as a case for a lithium-ion battery.As shown in FIG. 1, the square can 60 has a flat (or approximately flat) bottom wall 61 and a square tubular portion 65.

[0012] As shown in FIG. 1, the bottom wall 61 is formed in a substantially quadrangular (or rectangular) shape having a pair of bottom long sides 62 and a pair of bottom short sides 63 at its outer edge. The bottom long side portion 62 is a portion that extends linearly (or approximately linearly) along the long side direction. The bottom short side portion 63 is a portion that extends linearly (or approximately linearly) along the short side direction so as to form an angle of 90° with the bottom long side portion 62. Between the bottom long side portion 62 and the bottom short side portion 63, a bottom curved corner portion 64 is formed, which is curved convexly toward the outer periphery and smoothly connects the bottom long side portion 62 and the bottom short side portion 63. In this embodiment, each bottom curved corner portion 64 is curved with the same single R (single radius of curvature).

[0013] As shown in FIG. 1, the rectangular cylindrical portion 65 has a pair of long side walls 66 arranged opposite to each other in the short side direction, and a pair of short side walls 67 arranged opposite to each other in the long side direction. As shown in FIG. 1, each long side wall 66 is a flat (or approximately flat) portion formed to rise upward from the bottom long side portion 62, and the pair of long side walls 66 are formed parallel to each other. As shown in FIG. 1, each short side wall 67 is a flat (or approximately flat) portion formed to rise upward from the bottom short side portion 63 so as to form a 90° angle with the long side wall 66, and the pair of short side walls 67 are formed parallel to each other. Between the long side wall 66 and the short side wall 67, there is formed a corner wall 68 that is curved convexly on the outer periphery and that rises upward from the bottom curved corner portion 64 and smoothly connects the long side wall 66 and the short side wall 67. In this embodiment, each corner wall 68 is curved with the same single R (single radius of curvature). [Square can manufacturing method]

[0014] The method for manufacturing a rectangular can is for producing a rectangular can 60, and as shown in FIGS. 2 and 3 , includes a blank preparation step for preparing a blank 60A, a coining step for coining predetermined locations of the blank 60A, a first drawing step for applying a first drawing process to the blank 60A that has undergone the coining step, a second drawing step for applying a second drawing process to a cup-shaped first intermediate product 60B that has undergone the first drawing step, a drawing and ironing step for drawing and ironing a second intermediate product 60C obtained by the second drawing step, and a shape correction step for correcting the shape of a third intermediate product 60D obtained by the drawing and ironing step.

[0015] Each step of the method for manufacturing a rectangular can will be specifically described below.

[0016] First, in the blank preparation step, as shown in FIG. 2(a), a blank 60A as a metal plate is formed by punching a strip of metal such as aluminum.

[0017] In the coining step, as shown in FIG. 2(b), predetermined locations of the blank 60A are pressed in the thickness direction to perform coining to reduce the thickness. In this embodiment, the bottom wall portion of the blank 60A (the portion that will become the bottom wall 61 in the final molded product, the rectangular can 60) is subjected to coining processing to reduce the thickness by pressing in the thickness direction.

[0018] As shown in FIG. 2(c), the first drawing step is a step of forming a cup-shaped first intermediate product 60B by drawing the blank 60A that has been subjected to the coining step. Specifically, in the first drawing process, the blank 60A is held down from above by a blank holder 23, which functions as a wrinkle suppressor to prevent wrinkles from forming in the blank 60A, and the blank 60A is pushed (pulled in) from above by a punch 22 into a die-machined through-hole 21a formed in the die 21, thereby plastically deforming the blank 60A to form a cup-shaped first intermediate molded product 60B.

[0019] As shown in FIG. 3(d), the second drawing step is a step of forming a second intermediate product 60C by performing a second drawing process on the first intermediate product 60B obtained in the first drawing step. Specifically, in the second drawing process, the first intermediate molded product 60B is pressed from above (inside) by a blank holder 33 which functions as a wrinkle suppressor to prevent wrinkles from forming in the second intermediate molded product 60C, and the first intermediate molded product 60B is pushed (pulled) into a die machining through hole 31a formed in the die 31 by a punch 32, thereby plastically deforming the first intermediate molded product 60B to form the second intermediate molded product 60C. During this drawing, only the punch 32 and (a part of) the first intermediate formed product 60B are inserted into the die machining through-hole 31a, and the blank holder 33 is not inserted.

[0020] As shown in Figure 3(e), the drawing and ironing process involves drawing and ironing mainly the tubular portion 65C of the second intermediate molded product 60C (the portion that will become the square tubular portion 65 in the final molded product) in the gap between the die-machined through hole 41a formed in the die 41 and the punch 42 inserted into the die-machined through hole 41a to form the third intermediate molded product 60D. In the drawing and ironing step, a part of the bottom wall portion 61C of the second intermediate product 60C (a portion that will become the bottom wall 61 in the final product) is also subjected to drawing and ironing.

[0021] Specifically, in the drawing and ironing process, as shown in Figure 5, the second intermediate molded product 60C is pressed from above (inside) by a blank holder 43 which functions as a wrinkle suppressor to prevent wrinkles from forming in the third intermediate molded product 60D, and the punch 42 is moved relative to the die 41 (in this embodiment, the punch 42 and blank holder 43 are moved relative to the die 41 which is installed in a fixed state), so that the punch 42 pushes (pulls in) the second intermediate molded product 60C into the die-machined through hole 41a, and the second intermediate molded product 60C is plastically deformed in the gap between the die-machined inner surface 41b of the die-machined through hole 41a and the punch-machined outer surface 42a of the punch 42 to form the third intermediate molded product 60D. During the drawing and ironing process, only the punch 42 and (a part of) the second intermediate formed product 60C are inserted into the die processing through-hole 41a, and the blank holder 43 is not inserted.

[0022] As shown in FIGS. 4 and 5, the die 41 used in the drawing and ironing process has a die processing through-hole 41a formed so as to penetrate in the punch movement direction (vertical direction in this embodiment) during drawing and ironing. As shown in Figures 4 and 5, the die-machined through hole 41a has a die-machined inner surface 41b formed as a surface parallel to the punch movement direction (vertical direction), and a tapered machined surface 41f formed on the front side (upper side) of the die-machined inner surface 41b in the punch movement direction (vertical direction). As shown in Figures 4 to 6, the die processing inner surface 41b has a pair of die long side wall processing portions 41c that process the long side wall planned portion 66C of the second intermediate molded product 60C (the portion that will become the long side wall 66 in the final molded product), and a pair of die short side wall processing portions 41d that process the short side wall planned portion 67C of the second intermediate molded product 60C (the portion that will become the short side wall 67 in the final molded product). As shown in Figures 4 and 6(a), each die long side wall processing portion 41c is formed so as to extend linearly along the long side direction when viewed in the punch movement direction (up and down direction) (when the die 41 is cut in cross section along a plane perpendicular to the punch movement direction). As shown in Figures 4 and 6(a), each die short side wall processing portion 41d is formed so as to extend linearly along the short side direction when viewed in the punch movement direction (up and down direction) (when the die 41 is cut in cross section along a plane perpendicular to the punch movement direction). 4 and 6(a), a curved corner 41e is formed between the die long-side wall processing portion 41c and the die short-side wall processing portion 41d, and is curved convexly toward the outer periphery to smoothly connect the die long-side wall processing portion 41c and the die short-side wall processing portion 41d. This curved corner 41e functions as a portion for processing the vicinity of the corner wall prospective portion 68C of the second intermediate molded product 60C (the portion that will become the corner wall 68 of the rectangular tubular portion 65 in the final molded product state). In this embodiment, each curved corner 41e is curved with the same single radius of curvature (R). As shown in Figures 4 and 5, the tapered machining surface 41f is formed with an inclination so that the diameter decreases (the width in the long side direction and short side direction becomes narrower) as it goes toward the back (downward side) in the punch movement direction (up and down direction).

[0023] As shown in Figures 4 to 6, the punch 42 used in the drawing and ironing process has a punch processing outer peripheral surface 42a formed as a surface parallel to the punch movement direction (up and down direction) as an outer peripheral surface that faces the inner surface of the die processing through hole 41a during drawing and ironing. As shown in Figures 4 and 6(a), the punch processing outer surface 42a has a pair of punch long side wall processing portions 42b that work in cooperation with the die long side wall processing portion 41c to process the long side wall planned portion 66C of the second intermediate molded product 60C, and a pair of punch short side wall processing portions 42c that work in cooperation with the die short side wall processing portion 41d to process the short side wall planned portion 67C of the second intermediate molded product 60C.

[0024] As shown in Figure 6(a), each punch long side wall processing portion 42b has a processing top 42b-1 that is located at the outermost position in the short side direction among the punch long side wall processing portions 42b, and inclined portions 42b-2 that are formed on both sides of the long side direction of the processing top 42b-1 and are inclined so as to move inward in the short side direction as they move outward in the long side direction, and has an overall shape in which the center part in the long side direction bulges outward in the short side direction more than both ends in the long side direction. As shown in Figure 6(a), the processing top 42b-1 is formed at the center of the long side of the punch long side wall processing portion 42b (or near the center of the long side), and in this embodiment, it is formed as a part that extends linearly along the long side when viewed in the punch movement direction (up and down direction) (when the punch 42 is cut in cross section along a plane perpendicular to the punch movement direction). Furthermore, when the processed top portion 42b-1 is formed as a portion that extends linearly when viewed in cross section, the amount of deflection that occurs in the die long side wall processed portion 41c due to the forming reaction force during drawing and ironing can be reduced compared to when the processed top portion 42b-1 is formed as a point when viewed in cross section, as in the modified example shown in Figure 6(b). As shown in Figure 1, the inclined portion 42b-2 is formed as a portion that extends linearly when viewed in the punch movement direction (up and down direction) (when the punch 42 is viewed in cross section along a plane perpendicular to the punch movement direction).

[0025] As shown in Figure 6(a), each punch short side wall processing portion 42c is formed so as to extend linearly along the short side direction when viewed in the punch movement direction (up and down direction) (when the punch 42 is cut in cross section along a plane perpendicular to the punch movement direction).

[0026] Furthermore, a curved corner 42d is formed between the punch long-side wall processing portion 42b and the punch short-side wall processing portion 42c, and is curved convexly toward the outer periphery to smoothly connect the punch long-side wall processing portion 42b and the punch short-side wall processing portion 42c. The curved corner 42d functions as a portion for processing the vicinity of the corner wall prospective portion 68C of the second intermediate molded product 60C in cooperation with the curved corner 41e of the die 41. In this embodiment, each curved corner 42d is curved with the same single radius of curvature (R).

[0027] During the drawing and ironing process, the second intermediate molded product 60C is pushed (pulled) into the gap between the die long side wall processing portion 41c and the punch long side wall processing portion 42b, thereby performing an ironing process to reduce the plate thickness mainly on the long side wall intended portion 66C of the second intermediate molded product 60C, and the second intermediate molded product 60C is pushed (pulled) into the gap between the die short side wall processing portion 41d and the punch short side wall processing portion 42c, thereby performing a drawing process mainly on the vicinity of the corner wall intended portion 68C (and the short side wall intended portion 67C) of the second intermediate molded product 60C.

[0028] Here, when the flattening ratio (the ratio of the long side dimension to the short side dimension) of the die machining through hole 41a is high, as in this embodiment, as shown in Figure 7(a), during the drawing and ironing process, the molding reaction force causes the die long side wall processing portion 41c to bend so that the center of the long side of the die long side wall processing portion 41c moves outward in the short side direction.As a result, as shown in Figure 6(a), the short side direction spacing W1 between the die long side wall processing portion 41c and the punch long side wall processing portion 42b at the center of the long side of the die long side wall processing portion 41c becomes wider compared to the state when the punch 42 is inserted into the die machining through hole 41a under no load. Therefore, as shown in Figure 7(b), when the die long side wall processing portion 41c and the punch long side wall processing portion 42b are formed to extend linearly along the long side direction, and the short side direction spacings W1 and W2 between the die long side wall processing portion 41c and the punch long side wall processing portion 42b are set to be constant, the thickness of the long side wall planned portion 66C that has been subjected to the drawing and ironing process will be thick in the center in the long side direction and will become thinner toward both ends in the long side direction, making it impossible to achieve a uniform thickness distribution of the long side wall planned portion 66C. In contrast, in this embodiment, as shown in Figure 6(a), when the punch 42 is inserted into the die processing through hole 41a in an unloaded state (in other words, when the second intermediate molded product 60C is not interposed between the die long side wall processing portion 41c and the punch long side wall processing portion 42b and no molding reaction force is applied to the die 41 and punch 42), the short side direction spacing W1 between the long side center of the punch long side wall processing portion 42b and the die long side wall processing portion 41c is narrower than the short side direction spacing W2 between both long side direction ends of the punch long side wall processing portion 42b and the die long side wall processing portion 41c. As a result, during the drawing and ironing process, when the die long side wall processing portion 41c bends due to the molding reaction force, it is possible to reduce the dimensional difference between the short side direction spacing W2 between the die long side wall processing portion 41c at both ends of the long side direction and the punch long side wall processing portion 42b, and the short side direction spacing W1 between the die long side wall processing portion 41c at the center of the long side direction and the punch long side wall processing portion 42b, thereby making the thickness distribution of the molded long side wall planned portion 66C more uniform.

[0029] Furthermore, as shown in Figure 6(a), the die 41 and punch 42 are formed so that when the punch 42 is inserted into the die processing through hole 41a in an unloaded state, the short side direction spacing W1 between the long side center of the punch long side wall processing portion 42b and the die long side wall processing portion 41c is narrower than the long side direction spacing W3 between the punch short side wall processing portion 42c and the die short side wall processing portion 41d.

[0030] As shown in Figure 6(a), the die-machined inner surface 41b and the punch-machined outer surface 42a are each formed to be line-symmetrical in the long side direction and line-symmetrical in the short side direction when viewed in the punch movement direction (up and down direction). Furthermore, during the drawing and ironing process, the punch 42 is inserted into the die processing through hole 41a so that the long-side distances W1 and W2 between the die long-side wall processing portion 41c and the punch long-side wall processing portion 42b on both sides of the punch 42 in the long-side direction are the same, and the distance W3 between the die short-side wall processing portion 41d and the punch short-side wall processing portion 42c on both sides of the punch 42 in the short-side direction is the same.

[0031] As shown in Figure 3(f), the shape correction process involves widening (performing a widening process) the short-side distance between a pair of long-side wall planned portions 66D (portions that will become long-side walls 66 in the final molded product) of the third intermediate molded product 60D obtained by the drawing and ironing process, and flattening (bringing closer to a flat state, performing a flattening process) the bottom wall planned portion 61D (portion that will become the bottom wall 61 in the final molded product) of the third intermediate molded product 60D, to form a fourth intermediate molded product 60E.

[0032] In the shape correction process, as shown in FIG. 9, the shape correcting punch 52 is inserted into the third intermediate molded product 60D and then moved relative to the die 51 (in this embodiment, the shape correcting punch 52 is moved relative to the die 51, which is installed in a fixed state), and the third intermediate molded product 60D is pushed (pulled) into the die processing through hole 51a by the shape correcting punch 52, and the bottom wall planned portion 61D of the third intermediate molded product 60D is sandwiched between the shape correcting punch 52 and the bottom wall pressing member 53, in one process, to perform the above-mentioned widening processing and flattening processing.

[0033] Each step in the shape correction process will be specifically described below.

[0034] First, as shown in Figures 8 and 9, the widening process involves inserting a shape correcting punch 52 into the third intermediate molded product 60D, which is supported by an outer support member 54, and preventing a pair of short side wall planned portions 67D from approaching each other with the short side wall side pressing portion 52b of the shape correcting punch 52 inserted into the third intermediate molded product 60D, while pressing each long side wall planned portion 66D (particularly near the longitudinal center portion) outward in the short side direction with the long side wall pressing portion 52c of the shape correcting punch 52 inserted into the third intermediate molded product 60D, thereby widening the short side direction spacing between the pair of long side wall planned portions 66D (particularly between the long side direction center portions of the long side wall planned portions 66D) in a wedge shape. This widening process can correct the shape even if the so-called canning phenomenon occurs, in which the central portion of each long side wall 166 in the long side direction is recessed inward in the short side direction, as shown in FIG.

[0035] As shown in Figure 9, when the shape correcting punch 52 is inserted into the third intermediate molded product 60D, the short side wall side pressing portion 52b is positioned on the opening side of the third intermediate molded product 60D so as to press both side portions in the long side direction of each long side wall planned portion 66D and each short side wall planned portion 67D (portions that will become short side walls 67 in the final molded product) from the inside. As a result, when the shape correcting punch 52 is inserted into the third intermediate molded product 60D, the short side wall side pressing portion 52b functions to prevent (restrict) both side portions in the long side direction of the pair of long side wall planned portions 66D from approaching each other, and also to prevent (restrict) the pair of short side wall planned portions 67D from approaching each other. In addition, when the shape correcting punch 52 is inserted into the third intermediate molded product 60D, the short side wall side pressing portion 52b may be designed so as to expand the gap between both side portions in the long side direction of a pair of long side wall planned portions 66D in a wedge shape in the short side direction, or the short side wall side pressing portion 52b may be designed so as to expand the gap between a pair of short side wall planned portions 67D in a wedge shape in the long side direction. As shown in Figure 9, the short side wall side pressing portion 52b has a tapered portion at the rear (lower) side in the punch movement direction (up and down direction) that is inclined inward in the long side direction as it approaches the rear, making it easier to insert the shape correcting punch 52 into the third intermediate molded product 60D. In this embodiment, the short-side wall pressing portion 52b is formed as a separate member that is formed separately from the punch body 52a and fixedly attached to the punch body 52a, which makes it possible to easily adjust the degree of pressure applied by the short-side wall pressing portion 52b to the intended long-side wall portions 66D and the intended short-side wall portions 67D. However, the short-side wall pressing portion 52b may also be formed integrally with the punch body 52a.

[0036] As shown in Figure 9, when the shape correcting punch 52 is inserted into the third intermediate molded product 60D, the long side wall pressing portion 52c is positioned on the opening side of the third intermediate molded product 60D so as to press the central portion in the long side direction of each long side wall planned portion 66D from the inside. As a result, the long-side wall pressing portions 52c exert a function of widening the gap in the short-side direction between the pair of pre-long-side wall portions 66D. As shown in FIG. 9, the long side wall pressing portion 52c has a pressing surface whose central portion in the long side direction is positioned so as to bulge outward in the short side direction relative to both ends in the long side direction. Furthermore, as shown in Figure 9, the long side wall pressing portion 52c has a tapered portion at the rear (lower) side in the punch movement direction (up and down direction) that is inclined inward in the short side direction as it approaches the rear, making it easier to insert the shape correcting punch 52 into the third intermediate molded product 60D. In this embodiment, the long-side wall pressing portion 52c is formed as a separate member that is formed separately from the punch body 52a and fixedly attached to the punch body 52a, which makes it possible to easily adjust the degree of pressing of the long-side wall pressing portion 52c against the intended long-side wall portion 66D. However, the long-side wall pressing portion 52c may also be formed integrally with the punch body 52a.

[0037] In this embodiment, as shown in Figure 9, when the shape correcting punch 52 is inserted into the third intermediate molded product 60D, the short side wall side pressing portion 52b and the long side wall pressing portion 52c are described as being positioned at a position corresponding to the opening side (near the opening) of the third intermediate molded product 60D.However, the positioning of the short side wall side pressing portion 52b and the long side wall pressing portion 52c relative to the third intermediate molded product 60D when the shape correcting punch 52 is inserted into the third intermediate molded product 60D is not limited to the above, and for example, when the shape correcting punch 52 is inserted, the short side wall side pressing portion 52b and the long side wall pressing portion 52c may be positioned at a position corresponding to near the center of the third intermediate molded product 60D in the punch movement direction (up and down direction). Furthermore, the number of short side wall side pressing portions 52b and long side wall pressing portions 52c is not limited to those shown in Figures 8 and 9. For example, in addition to those shown in Figures 8 and 9, additional short side wall side pressing portions 52b and long side wall pressing portions 52c may be provided so as to be positioned at a position corresponding to the center of the third intermediate molded product 60D in the punch movement direction (vertical direction) when the shape correcting punch 52 is inserted.

[0038] As shown in Figure 9, the outer support member 54 supports the flange portion 69D of the third intermediate molded product 60D from below during the widening process, and is positioned so as to press both side portions in the long side direction of each long side wall planned portion 66D from the outside on the opening side (near the opening) of the third intermediate molded product 60D. As a result, when the shape correcting punch 52 is inserted into the third intermediate molded product 60D, the outer support member 54 supports the third intermediate molded product 60D and also functions to prevent (restrict) both side portions in the long side direction of each long side wall planned portion 66D from spreading outward in the short side direction.

[0039] Depending on the embodiment, instead of or in addition to the outer support members 54, other support members may be provided to support the third intermediate molded product 60D from the outside at any position.

[0040] In the flattening process, the shape correcting punch 52 is moved, and the bottom wall portion 61D is sandwiched between the bottom wall pressing portion 52d of the shape correcting punch 52 inserted into the third intermediate molded product 60D and the bottom wall pressing member 53 arranged on the outer surface side of the bottom wall portion 61D, and the third intermediate molded product 60D (the bottom wall portion 61D of the third intermediate molded product 60D and a part of the cylindrical portion 65D near the bottom wall portion 61D) is pressed into the die processing through hole 51a by the shape correcting punch 52. By pushing (pulling) the third intermediate molded product 60D into the die 51, a drawing and ironing process is performed around the entire circumferential area near the connection (curved corner) between the planned cylindrical portion 65D and the planned bottom wall portion 61D of the third intermediate molded product 60D (region R shown in Figure 9) in the gap between the die-processed inner peripheral surface of the die-processed through hole 51a formed in the die 51 and the punch-processed outer peripheral surface of the shape correcting punch 52 inserted into the die-processed through hole 51a, thereby flattening the planned bottom wall portion 61D.

[0041] The pressing surfaces of the bottom wall pressing portion 52d of the shape correcting punch 52 and the bottom wall pressing member 53, which sandwich the pre-bottom wall portion 61D, are each formed flat. Although the bottom wall pressing portion 52d of the shape correcting punch 52 is formed integrally with the punch body 52a, the bottom wall pressing portion 52d may be formed from a separate member formed separately from the punch body 52a. The bottom wall pressing member 53 is supported by an air cylinder (not shown), and when pressed downward by the punch (third intermediate molded product 60D) during flattening, it moves downward together with the punch (third intermediate molded product 60D) and applies an appropriate amount of pressure (pressure) to the bottom wall portion 61D by sandwiching the bottom wall portion 61D between itself and the shape correcting punch 52. During the flattening process described above, the impact when the punch (third intermediate molded product 60D) collides with the bottom wall pressing member 53 is alleviated by the air cylinder (not shown).

[0042] In addition, in the first and second drawing processes and the drawing and ironing process described above, no equipment is used to support the outside (lower side) of the bottom wall portion, which corresponds to the bottom wall pressing member 53 (and air cylinder), i.e., no equipment is used to clamp the bottom wall portion 61D with the punch moving downward.

[0043] In the shape correction process of this embodiment as described above, after the shape correction punch 52 is inserted into the third intermediate molded product 60D, the shape correction punch 52 is moved toward the die 51 and the bottom wall pressing member 53. This makes it possible to perform shape correction (widening processing) of the planned tubular portion 65D and shape correction (flattening processing) of the planned bottom wall portion 61D together in one process (one operation), thereby improving the shape accuracy of the square can 60 while minimizing the increase in manufacturing burden. In addition, during drawing or drawing and ironing, it is possible to suppress outward bulging of the bottom wall by sandwiching the bottom wall portion of the intermediate product between a punch and a member installed outside the bottom wall portion, but such a configuration requires a large punch stroke length for drawing or drawing and ironing, and the member installed outside (below) the bottom wall portion must be designed to move in accordance with the movement of the punch, resulting in increased equipment costs and a slower production speed.In contrast, the present invention does not require such a structure, and the stroke length of the bottom wall pressing member 53 is short, making it possible to avoid increased equipment costs and a slower production speed.

[0044] In addition to the above processes, the square can manufacturing method also includes various other processes, such as a trimming process for cutting off unnecessary portions near the opening, such as the flange portion, of the fourth intermediate molded product 60E obtained by the shape correction process, and a cleaning process. [Square can manufacturing equipment 10]

[0045] Next, the prismatic can manufacturing apparatus 10 will be described below.

[0046] As shown in Figures 2 and 3, the square can manufacturing apparatus 10 includes a first drawing unit 20 for performing the first drawing process, a second drawing unit 20 for performing the second drawing process, a drawing and ironing unit 40 for performing the drawing and ironing process, and a shape correction unit 50 for performing the shape correction process.

[0047] As shown in FIGS. 2 and 3, the first and second drawing units 20, 30 and the drawing and ironing unit 40 include dies 21, 31, 41, punches 22, 23, 24, blank holders 23, 33, 43, and various peripheral equipment such as drive means including actuators and motors for driving each part of the punches and other components, and support members. As shown in FIG. 4, the shape correction unit 50 includes a die 51, a shape correction punch 52, a bottom wall pressing member 53, an outer support member 54, and various peripheral equipment such as driving means including actuators and motors for driving each part of the punch and other components, and support members. The specific configurations and functions of these components are as described above.

[0048] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments. Various design modifications can be made without departing from the scope of the present invention as defined in the claims, such as configuring a square can manufacturing method and a square can manufacturing apparatus 10 by arbitrarily combining the respective components of the above-described or following embodiments and modified examples.

[0049] For example, in the above-described embodiment, it has been described that two drawing processes (or drawing and ironing processes) are performed before the drawing and ironing process, but the number of drawing processes (or drawing and ironing processes) performed before the drawing and ironing process may be one, three or more.

[0050] In addition, in the above-described embodiment, the die long side wall processing portion 41c is formed to extend linearly along the long side direction, and the punch long side wall processing portion 42b is formed to have an overall shape in which its center in the long side direction is positioned bulging outward in the short side direction more than both ends in the long side direction.This has been described as making it so that when the punch 42 is inserted into the die processing through hole 41a in an unloaded state, the short side direction spacing W1 between the long side direction center of the punch long side wall processing portion 42b and the die long side wall processing portion 41c is narrower than the short side direction spacing W2 between both ends in the long side direction of the punch long side wall processing portion 42b and the die long side wall processing portion 41c. However, the specific form of the long side wall processing portions 41c, 42b is not limited to the above, and any form may be used as long as the distance W1 is narrower than the distance W2 in the above state. For example, if the punch long side wall processing portion 42b is formed to have an overall shape in which the center in the long side direction is bulged outward in the short side direction from both ends in the long side direction, the die long side wall processing portion 41c may be formed in a shape other than a shape extending linearly along the long side direction (for example, an overall shape in which the center in the long side direction is bulged outward in the short side direction from both ends in the long side direction, or an overall shape in which the center in the long side direction is bulged inward in the short side direction from both ends in the long side direction). In addition, the die long side wall processing portion 41c may be formed to have an overall shape in which the center in the long side direction is positioned bulging inward in the short side direction relative to both end sides in the long side direction, so that the spacing W1 is narrower than the spacing W2 in the above state.In this case, the shape of the punch long side wall processing portion 42b may be various shapes, such as a shape that extends linearly along the long side direction, an overall shape in which the center in the long side direction is positioned bulging outward in the short side direction relative to both end sides in the long side direction, or an overall shape in which the center in the long side direction is positioned bulging inward in the short side direction relative to both end sides in the long side direction.

[0051] Furthermore, when the punch long side wall processing portion 42b is formed to have an overall shape in which the center in the long side direction is positioned bulging outward in the short side direction relative to both ends in the long side direction, the specific form of the punch long side wall processing portion 42b is not limited to that of the above-mentioned embodiment. For example, in the example shown in Figure 6(a), the processed top portion 42b-1 is formed as a portion that extends linearly along the long side direction when viewed in cross section, but as in the modified example shown in Figure 6(b), the processed top portion 42b-1 may be a point-like portion when viewed in cross section. Furthermore, in the example shown in Figure 6(a), the inclined portion 42b-2 is formed as a portion that extends in a straight line when viewed in cross section, but as in the modified example shown in Figure 6(b), the inclined portion 42b-2 may be a portion that extends in a curved line when viewed in cross section, or the inclined portion 42b-2 may be formed as a portion that is made up of a combination of one or more straight lines and one or more curves when viewed in cross section. In the modified example shown in Figure 6(b), the punch long side wall processing portion 42b is formed in a so-called drum shape, with the entire portion curved convexly outward in the short side direction so that the center in the long side direction is positioned more outward in the short side direction than both ends in the long side direction.

[0052] Similarly, when the die long side wall processing portion 41c is formed as having an overall shape having a processed top (located at the innermost position in the short side direction of the die long side wall processing portion 41c) and inclined portions (formed on both sides of the processed top in the long side direction and inclined so as to move outward in the short side direction as they move outward in the long side direction), and the center in the long side direction is positioned bulging more inward in the short side direction than both ends in the long side direction, the processed top of the die long side wall processing portion 41c may be formed as a portion that extends linearly along the long side direction when viewed in cross section, or may be formed as a point-like portion when viewed in cross section. Furthermore, the inclined portion of the die long side wall processing portion 41c may be formed as a portion that extends in a straight line when viewed in cross section, or as a portion that extends in a curved line when viewed in cross section, or as a portion that is a combination of one or more straight lines and one or more curves when viewed in cross section.

[0053] Furthermore, in the above-described embodiment, the die short side wall processing portion 41d and the punch short side wall processing portion 42c are described as being formed to extend linearly along the long side direction, but these processing portions may also be formed in other shapes (for example, curved shapes when viewed in the punch movement direction). Furthermore, in the above-described embodiment, the die-machined inner peripheral surface 41b and the punch-machined outer peripheral surface 42a are described as being formed as surfaces parallel to the punch movement direction (vertical direction), but the specific forms of the die-machined inner peripheral surface 41b and the punch-machined outer peripheral surface 42a are not limited to this. [Explanation of symbols]

[0054] 10 Square can manufacturing equipment 20 First aperture unit 21 ··· Die 21a: Die-machined through hole 22 Punch 23 Blank holder 30 Second aperture unit 31 ··· Die 31a: Die-machined through hole 32 Punch 33 Blank holder 40 Squeezing and ironing unit 41 ··· Die 41a: Die-machined through hole 41b: Die-machined inner surface 41c Die long side wall processing section 41d: Die short side wall processing section 41e ··· Curved corner 41f Tapered surface 42 Punch 42a... Punched outer surface 42b: Punch long side wall processing section 42b-1 ··· Machining top 42b-2 ··· Inclined section 42c Punch short side wall processing section 42d ··· Curved corner 43 Blank holder 50 ··· Shape correction unit 51 ··· Die 51a: Die-machined through hole 52 ··· Shape correction punch 52a Punch body 52b: Short side wall holding portion 52c Long side wall pressing part 52d Bottom wall pressing part 53 Bottom wall pressing member 54 Outer support member 60 ··· Square can (final molded product) 61 Bottom wall 62 ... bottom long side 63 Bottom short side 64 ... Bottom curved corner 65 Square cylindrical section 66 Long side wall 67 Short side wall 68 Corner wall 60A Blank 60B 1st intermediate molded product 60C...Second intermediate molded product 61C: Bottom wall planned section 65C - Cylindrical section 66C Long side wall planned section 67C ··· Short side wall planned section 68C Corner wall planned section 60D 3rd intermediate molded product 61D: Bottom wall planned section 65D - Cylindrical section 66D Long side wall planned section 67D: Short side wall planned section 69D Flange part 60E 4th intermediate molded product

Claims

1. A method for manufacturing a rectangular can having a rectangular tubular portion having a bottom wall, a pair of long side walls, and a pair of short side walls, comprising the steps of: The method for manufacturing a rectangular can includes a drawing and ironing step of drawing and ironing a portion to be formed into a cylindrical portion of an intermediate product in a gap between a die-processed inner peripheral surface of a die-processed through hole formed in a die and a punch-processed outer peripheral surface formed on a punch inserted into the die-processed through hole, The die processing inner peripheral surface has a die long side wall processing portion that processes a long side wall planned portion of the intermediate molded product, and a die short side wall processing portion that processes a short side wall planned portion of the intermediate molded product, the punched outer peripheral surface has a punch long side wall processing portion that processes the long side wall planned portion, a punch short side wall processing portion that processes the short side wall planned portion, and a curved corner portion that smoothly connects the punch long side wall processing portion and the punch short side wall processing portion, a die and a punch formed in a rectangular can manufacturing method, characterized in that, when the punch is inserted into the die processing through-hole under no load, the short-side distance between the long-side center of the punch long-side wall processing portion and the die long-side wall processing portion is narrower than the short-side distance between both long-side ends of the punch long-side wall processing portion and the die long-side wall processing portion.

2. 2. The method for manufacturing a rectangular can according to claim 1, wherein the punch long-side wall processed portion has a processed apex portion located at the outermost position in the short-side direction of the punch long-side wall processed portion, and inclined portions formed on both sides of the processed apex in the long-side direction and inclined toward the inside in the short-side direction as they extend outward in the long-side direction, and a central portion in the long-side direction of the processed apex portion bulges outward in the short-side direction.

3. 3. The method for manufacturing a rectangular can according to claim 2, wherein the processed top portion is a portion that extends linearly along the long side direction when viewed in cross section.

4. The die processing inner peripheral surface has a die short side wall processing portion that processes a planned short side wall portion of the intermediate molded product, The punched outer peripheral surface has a punch short side wall processing portion that processes the short side wall planned portion, 4. The method for manufacturing a rectangular can according to claim 1, wherein the die and the punch are formed so that, when the punch is inserted into the die processing through hole under no load, the short-side distance between the long-side center of the punch long-side wall processing portion and the die long-side wall processing portion is narrower than the long-side distance between the punch short-side wall processing portion and the die short-side wall processing portion.

5. A square can manufacturing apparatus for manufacturing square cans each having a square tubular portion having a bottom wall, a pair of long side walls, and a pair of short side walls, the prismatic can manufacturing apparatus includes a drawing and ironing unit that draws and irons a portion to be formed into a cylindrical portion of an intermediate product in a gap between a die-processed inner peripheral surface of a die-processed through hole formed in a die and a punch-processed outer peripheral surface formed on a punch inserted into the die-processed through hole, The die processing inner peripheral surface has a die long side wall processing portion that processes a long side wall planned portion of the intermediate molded product, and a die short side wall processing portion that processes a short side wall planned portion of the intermediate molded product, the punched outer peripheral surface has a punch long side wall processing portion that processes the long side wall planned portion, a punch short side wall processing portion that processes the short side wall planned portion, and a curved corner portion that smoothly connects the punch long side wall processing portion and the punch short side wall processing portion, The die and the punch are formed so that, when the punch is inserted into the die processing through-hole under no load, the short-side distance between the long-side center of the punch long-side wall processing portion and the die long-side wall processing portion is narrower than the short-side distance between both long-side ends of the punch long-side wall processing portion and the die long-side wall processing portion.

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