JP7609701B2 - Manufacturing method for bottomed cylindrical parts - Google Patents

Description

The present invention relates to a method for manufacturing a bottomed tubular part.

Patent documents 1 and 2 disclose that an automobile battery pack case, which is an example of a cylindrical part with a bottom, is manufactured by press molding a plate material such as an aluminum alloy.

Patent Publication 2014-60165 Patent Publication 2019-18732

Automotive battery pack cases manufactured by press molding have, for example, a flanged, bottomed rectangular cylinder shape. This type of battery pack case requires a sharp, deep shape to ensure sufficient battery capacity. It also requires sealing properties to prevent electrical leakage.

For a sharp, deep shape, it is important to reduce the radius (shoulder radius) of the connection between the main body in which the battery is housed and the flange extending from the opening of the main body. The maximum size of the battery pack case is restricted by the size of the vehicle's framework (e.g., side sills, A-pillars, B-pillars). To increase the battery capacity under these conditions, it is important to reduce the shoulder radius and reduce the gap between the battery pack case and the mating member that supports it (e.g., battery pack frame or side sill).

To ensure a good seal, it is important that there are no wrinkles in the flange area.

However, Patent Documents 1 and 2 do not specifically mention how to achieve both a sharp, deep shape and the absence of wrinkles in the flange portion when manufacturing a bottomed tubular part by press molding a metal plate.

The objective of the present invention is to provide a method for manufacturing a bottomed tubular part that can achieve both a sharp, deep shape and a wrinkle-free flange portion.

One aspect of the present invention is a manufacturing method for a bottomed tubular part having a bottomed tubular main body and a flange portion extending from an opening of the main body, the method comprising: a first step of obtaining an intermediate formed body from a sheet material by drawing using a first die having a first die shoulder radius larger than a product shoulder radius, which is the radius of the connection portion between the main body and the flange portion, and a first die depth deeper than a product depth, which is the depth of the main body; and a second step of obtaining the bottomed tubular part from the intermediate formed body by drawing using a second die having a second die shoulder radius the same as the product shoulder radius and having a second die depth the same as the product depth, wherein the corner radius of the bottomed angular tube shape is 20 mm or more, the initial sheet thickness of the blank is 1.0 mm or more, and the first die depth satisfies the following formula .

In the first step, a first die having a first die shoulder radius larger than the product shoulder radius is used, which promotes the flow of material into the body of the intermediate compact, and ensures the molding depth of the body of the intermediate compact. As a result, the product depth of the bottomed tubular part, which is the final product, can be set deep. In addition, by using a first die having a first die shoulder radius larger than the product shoulder radius in the first step and using a second die having a second die shoulder radius the same as the product shoulder radius in the subsequent second step, the product shoulder radius of the bottomed tubular part, which is the final product, can be set small. In this way, according to the present invention, a bottomed tubular part having a sharp and deep shape can be manufactured.

In the first step, a first die having a first die shoulder radius larger than the product shoulder radius is used to ensure the forming depth, whereas in the second step, a second die having a second die shoulder radius equal to the product shoulder radius is used. In other words, the product shoulder radius (corresponding to the first die shoulder radius) of the intermediate formed body is reduced to the product shoulder radius (corresponding to the second die shoulder radius) of the final product by the second step. This means that material needs to be supplied to the shoulder of the intermediate formed body in the second step. However, the first die depth of the first die used in the first step is deeper than the product depth of the bottomed tubular part which is the final product. In other words, the product depth of the intermediate formed body provided in the second step is deeper than the product depth of the bottomed tubular part which is the final product, and the depth of the main body is reduced by the second step. Therefore, in the second step, the material to be supplied to the connection portion between the main body and the flange portion in order to reduce the product shoulder radius from the size corresponding to the first die shoulder radius to the size corresponding to the second die shoulder radius can be ensured by the outflow of material from the main body. In other words, the material to be supplied to the connection between the main body and the flange in order to reduce the die shoulder radius from the first die shoulder radius to the second die shoulder radius in the second step is not secured by the inflow of material from the flange. By reducing or eliminating the inflow of material from the flange, the occurrence of wrinkles in the flange can be prevented.

As described above, according to the present invention, it is possible to achieve both a sharp and deep shape and a flange portion without wrinkles.

The plate may be made of aluminum.

The manufacturing method of the bottomed tubular part of the present invention makes it possible to achieve both a sharp, deep shape and a wrinkle-free flange portion.

FIG. 2 is a perspective view of a bottomed rectangular tubular part manufactured by a manufacturing method according to an embodiment of the present invention. FIG. 1B is a cross-sectional view taken along line II of FIG. FIG. 4 is a perspective view of a die used in a first drawing step of the manufacturing method according to the embodiment of the present invention. FIG. 2B is a cross-sectional view taken along line II-II of FIG. 2A. FIG. 4 is an exploded perspective view illustrating a first drawing step of the manufacturing method according to the embodiment of the present invention. FIG. 4 is a perspective view of a die used in a second drawing step of the manufacturing method according to the embodiment of the present invention. FIG. 4B is a cross-sectional view taken along line IV-IV in FIG. 4A. FIG. 4 is an exploded perspective view illustrating a second drawing step in the manufacturing method according to the embodiment of the present invention. 2 is a schematic cross-sectional view taken along line II in FIG. 1 for explaining a change in line length after a second drawing process. 13 is a graph showing the results of a forming analysis regarding the relationship between the deviation of the forming height from a reference value in the first process and the occurrence of breakage and wrinkles. FIG. 4 is a perspective view of a die used in the manufacturing method according to the first comparative example. FIG. 7B is a cross-sectional view taken along line VII-VII in FIG. 7A. FIG. 11 is a perspective view of a die used in a first drawing step of a manufacturing method according to a second comparative example. FIG. 8B is a cross-sectional view taken along line VIII-VIII in FIG. 8A.

The manufacturing method according to an embodiment of the present invention will be described below with reference to the attached drawings.

Referring to Figures 1A and 1B, in the manufacturing method of this embodiment, an aluminum plate is press-formed to produce a bottomed rectangular tubular part 1. The bottomed rectangular tubular part 1 can be used as a battery pack case, which is an example of an automotive component.

The bottomed rectangular tubular part 1 has a main body 1a that is a bottomed rectangular tubular body of a certain depth, and a flange portion 1b that extends outward from the entire circumference of the opening of the main body 1a.

In this embodiment, the main shape and dimensions of the bottomed rectangular tubular part 1 are as follows:

In this embodiment, a 5000 series aluminum plate with a thickness of 1 mm was used, but the plate thickness and alloy type are not limited to this.

In this embodiment, the bottom of the main body 1a is a square with a side length of 600 mm. The side length is not limited to 600 mm. The bottom of the main body 1a may be rectangular.

In this embodiment, the depth of the main body 1a (product depth PD) is 70 mm. The product depth PD is not limited to 70 mm.

In this embodiment, the radius of the connection portion between the main body 1a and the flange portion 1b, i.e., the radius of the product shoulder portion 1c (product shoulder radius PSR) is 2 mm. The product shoulder radius PSR is not limited to 2 mm.

In this embodiment, the radius of the connection between the bottom and side of the main body 1a (product bottom radius PBR) is 10 mm. The product bottom radius PBR is not limited to 10 mm.

In this embodiment, the radius of the bottom corner of the main body 1a (product corner radius PCR1) is approximately 52 mm. The product corner radius PCR1 is not limited to approximately 52 mm.

In this embodiment, the radius of the corner formed by the two sides of the main body 1a (product corner radius PCR2) is 20 mm. The product corner radius PCR2 is not limited to 20 mm.

The corner radius (product corner radius PCR3) formed by the connection between the side and bottom of the main body 1a 2 is 25 mm at the center and tapers to 10 mm at the radius end. The dimensions of the product corner radius PCR3 are not limited to those in this embodiment.

In the manufacturing method of this embodiment, a square cylindrical part 1 with a base is manufactured from a blank 2 (see Figure 3), which is an aluminum plate material, by two drawing processes (first and second processes).

(First step)
The first step will be described with reference to FIGS. 2A to 3.

The first die 3 used in the first step has a die body 3a for forming the main body 1a of the bottomed rectangular tubular part 1, which is the final product, and a die flange portion 3b for forming the flange portion 1b of the bottomed rectangular tubular part 1.

The radius (first die shoulder radius DSR1) of the die shoulder 3c, which is the connection portion between the die body 3a and the die flange portion 3b, is set to be larger than the product shoulder radius PSR. Specifically, in this embodiment, the product shoulder radius PSR is 2 mm as described above, while the first die shoulder radius DSR1 is set to 15 mm. The first die shoulder radius DSR1 is set to satisfy the condition that it is larger than the product shoulder radius PSR.

The depth of the die body 3a (first die depth DD1) is set deeper than the product depth PD. Specifically, in this embodiment, the product depth PD is 70 mm as described above, while the first die depth DD1 is set to 75 mm. The first die depth DD1 is set to satisfy the condition that it is deeper than the product depth PD.

The other shapes and dimensions of the first die 3 are set to correspond to the shape and dimensions of the bottomed rectangular tubular part 1 described with reference to Figures 1A and 1B, i.e., the final product.

Referring to FIG. 3, in the first step, the peripheral portion of the blank 2 is sandwiched and held between the die flange portion 3b of the first die 3 and a rectangular frame-shaped holder 4. In this state, pressure is applied to the blank 2 by the first punch 5, as conceptually shown by the arrow F in FIG. 3.

The shape and dimensions of the first punch 5 are set according to the first die 3.

The pressure applied by the first punch 5 causes the blank 1 to deform into the shape of the first die 3, and an intermediate formed body 6 (see Figure 5) is obtained. The intermediate formed body 6 has a main body 6a which will become the main body 1a in the final product, the bottomed rectangular tubular part 1, and a flange portion 6b which will become the flange portion 1b in the bottomed rectangular tubular part 1. The radius of the shoulder portion 6c (intermediate formed body shoulder radius MSR), which is the connection portion between the main body 6a and the flange portion 6b in the intermediate formed body 6, is the same as the first die shoulder radius DSR1 (15 mm in this embodiment). In addition, the depth of the main body 6a of the intermediate formed body 6 (intermediate formed body depth MD) is the same as the first die depth DD1.

(Second step)
The second step will be described with reference to FIGS. 4A to 5.

The second die 7 used in the second step has a die body 7a for forming the main body 1a of the bottomed rectangular tubular part 1, which is the final product, and a die flange portion 7b for forming the flange portion 7b of the bottomed rectangular tubular part 1.

The radius (second die shoulder radius DSR2) of the die shoulder 7c, which is the connection portion between the die body 7a and the die flange portion 7b, is set to be the same as the product shoulder radius PSR. Specifically, in this embodiment, since the product shoulder radius PSR is 2 mm as described above, the second die shoulder radius DSR2 is set to 2 mm. Also referring to FIG. 6, the second die shoulder radius DSR2 of the second die 7 used in the second process is smaller (2 mm in this embodiment) than the first die shoulder radius DSR1 of the first die 3 used in the first process (15 mm in this embodiment).

The depth of the die body 7a (second die depth DD2) is set to the same as the product depth PD. Specifically, in this embodiment, since the product depth PD is 70 mm as described above, the second die depth DD2 is set to 70 mm. Referring to FIG. 5, the second die depth DD2 of the second die 7 used in the second process is shallower (70 mm in this embodiment) than the first die depth DD1 of the first die 3 used in the first process (75 mm in this embodiment).

The other shapes and dimensions of the second die 7 are set to correspond to the shape and dimensions of the bottomed rectangular tubular part 1 described with reference to Figures 1A and 1B, i.e., the final product.

Referring to FIG. 5, the intermediate compact 6 is placed on the second punch 8. In this state, as conceptually shown by the arrow F in FIG. 5, the second die 7 moves toward the second punch 8, thereby applying pressure to the intermediate compact 6.

The second punch 8 comprises a punch body 8a and a punch flange portion 8b extending outward from the entire circumference of the punch body 8a. The radius of the punch shoulder portion 8c, which is the connection portion between the punch body 8a and the punch flange portion 8b (second punch shoulder radius PUSR2) is set based on the second die shoulder radius DSR2 and taking into account the plate thickness. In addition, the depth of the punch body 8a (second punch depth PUD2) is set to be the same as the second die depth DD2.

The pressure applied by the second die 7 moving toward the second punch 8 causes the intermediate formed body 6 to deform into the shape of the second die 7, resulting in the final product, a square cylindrical part 1 with a bottom (see Figures 1A and 1B).

Below, the features of the manufacturing method of this embodiment will be explained while comparing two comparative examples, namely, a first comparative example shown in Figures 7A and 7B and a second comparative example shown in Figures 8A and 8B.

In this embodiment, a first process is performed, which is a drawing process using a first die 3 having a first die shoulder radius DSR1 larger than the product shoulder radius PSR of the bottomed rectangular tubular part 1, which is the final product, and a first die depth DD1 deeper than the product depth PD of the bottomed rectangular tubular part 1. Then, a second process is performed, which is a drawing process using a second die 8 having a second die shoulder radius DSR2 the same as the product shoulder radius PSR and a second die depth DD2 the same as the product depth PD.

In contrast, in the first comparative example, only one drawing process corresponding to the first step in this embodiment, that is, only one drawing process is performed on the blank. Also, in the first comparative example, as shown in Figures 7A and 7B, a first die 3 is used that has a first die shoulder radius DSR1 that is the same as the product shoulder radius PSR and a first die depth DD1 that is the same as the product depth PD.

Next, in the second comparative example, drawing is performed on a blank, which corresponds to the first step in this embodiment, and drawing is performed on an intermediate formed body, which corresponds to the second step. The difference between the second comparative example and this embodiment is that, as shown in Figures 8A and 8B, the first die depth DD1 of the first die 3 used in the first step is the same as the product depth PD of the bottomed rectangular tubular part 1, which is the final product (the first die shoulder radius DSR1 is larger than the product shoulder radius PSR).

According to a simulation performed by the inventor, in the first comparative example, the blank breaks before reaching the first product depth PD, and the final product, the bottomed tubular part 1, is not obtained.

In addition, according to the above simulation, in the second comparative example, although a bottomed tubular part 1 is obtained, wrinkles occur in the flange portion 1b. This is because the second die shoulder radius DSR2 in the second process is smaller (2 mm) than the first die shoulder radius DSR1 (15 mm) in the first process, and therefore the material to be supplied to the shoulder portion 6c of the intermediate compact 6 in the second process is secured by the material flowing in from the flange portion 6b.

On the other hand, according to the above simulation, in the manufacturing method of this embodiment, the first die 3 having the first die shoulder radius DSR1 larger than the product shoulder radius PSR is used in the first step, which promotes the flow of material into the main body 6a of the intermediate compact 6 and ensures the intermediate compact depth MD. As a result, the product depth PD of the bottomed tubular part 1 can be set deep without causing breakage of the blank as in the first comparative example. In addition, in the manufacturing method of this embodiment, the first die 3 having the first die shoulder radius DSR1 larger than the product shoulder radius PSR is used in the first step, and the second die 7 having the second die shoulder radius DSR2 the same as the product shoulder radius PSR is used in the subsequent second step, which allows the product shoulder radius PSR of the bottomed tubular part 1, which is the final product, to be set small. In this way, according to the manufacturing method of this embodiment, a bottomed square tubular part 1 with a sharp and deep shape can be manufactured.

Next, according to the above simulation, in the manufacturing method of this embodiment, in the first step, a first die 3 having a first die shoulder radius DSR1 larger than the product shoulder radius PSR is used to ensure the molding depth, but in the second step, a second die 7 having a second die shoulder radius DSR2 equal to the product shoulder radius PSR is used. In other words, the intermediate molded body shoulder radius MSR1 (corresponding to the first die shoulder radius DSR1) of the intermediate molded body 6 is reduced to the product shoulder radius PSR (corresponding to the second die shoulder radius DSR2) of the final product by the second step. This means that material needs to be supplied to the shoulder 6c of the intermediate molded body 6 in the second step. However, the first die depth DD1 of the first die 3 used in the first step is deeper than the product depth PD of the final product. In other words, the intermediate molded body depth MD of the intermediate molded body 6 provided in the second step is deeper than the product depth PD of the final product, and the depth of the main body is reduced by the second step. Therefore, in the second step, in order to reduce the intermediate shoulder radius MSR1 of the intermediate body 6 to the product shoulder radius PSR of the final product, the material to be supplied to the shoulder 6c of the intermediate body 6 can be secured by the outflow of material from the main body 6a. In other words, in the second step, in order to reduce the die shoulder radius from the first die shoulder radius DSR1 to the second shoulder radius DSR2, the material to be supplied to the shoulder 6c of the intermediate body 6 is not secured by the inflow of material from the flange portion 6b. By reducing or eliminating the inflow of material from the flange portion 6b, the occurrence of wrinkles in the flange portion 1b of the final product can be prevented.

As described above, the manufacturing method of this embodiment can achieve both a sharp, deep shape and a wrinkle-free flange portion 1b.

Referring to FIG. 6A, in the manufacturing method of this embodiment, the change in line length caused by reducing the die shoulder radius from the first die shoulder radius DSR1 to the second die shoulder radius DSR2 in the second process, and therefore the difference ΔDD between the first die depth DD1 and the second die depth DD2 (corresponding to the difference in forming depth between the first process and the second process), is expressed by the following formula (1) based on the geometric relationship.

From this formula (1), when the first die shoulder radius DSR1 is 15 mm and the second die shoulder radius DSR2 is 2 mm, the difference ΔDD between the first die depth D number 1 and the second die depth DD2 is approximately 5.57 mm.

Furthermore, from equation (1), the first die depth DD1 is expressed by the second die depth DD2, the first die shoulder radius DSR1, and the second die shoulder radius DSR2 as shown in the following equation (2).

The first die depth DD1 is defined by formula (2), but some error occurs in the actual process. Therefore, a simulation was conducted to examine to what extent this error can be tolerated. The results are shown in Figure 6B. As shown in Figure 6B, when the deviation of the forming height in the first process (equal to the first die depth DD1) from the reference value (the value obtained from formula (2)) was in the range of -2.54 mm to +2.42 mm, no wrinkles were generated in the final product.

In this study, the initial plate thickness is set to 1.0 mm as mentioned above, and the product corner radius RCR2 of the bottomed rectangular cylinder (see Figure 1A) is set to 20 mm as mentioned above. In general, wrinkles in cylindrical shapes are affected by the plate thickness and the size of the corner radius, and the thinner the plate thickness and the smaller the corner radius, the more likely wrinkles are to occur. Therefore, when forming a bottomed rectangular cylinder using the results obtained in this study, if the product corner radius RCR2 is 20 mm or more and the blank plate thickness is 1.0 mm or more, wrinkles will not occur in the flange portion if the forming height in the first process, i.e., the first die depth DD1, satisfies the following formula (3).

Here, DD1 is the first die depth, DD2 is the second die depth (the forming height of the final product), DSR1 is the first die shoulder radius, and DSR2 is the second die shoulder radius (the shoulder radius of the final product). The units in the above formula are "mm."

The bottomed rectangular tubular part manufactured by the manufacturing method of this embodiment can be used as a battery pack case for an automobile, but the application of the present invention is not limited to this. The present invention is preferably applied to the manufacture of components whose maximum dimensions are reduced in consideration of the surrounding components, and whose internal volume must be maximized. Examples of such components include battery pack lids, side door inner panels, converter cases, and other automobile components such as motor cases (bottomed cylindrical containers).

1 Bottomed square cylindrical part (bottomed cylindrical part)
Reference Signs List 1a Body 1b Flange 1c Product shoulder 2 Blank 3 First die 3a Die body 3b Die flange 3c Die shoulder 4 Holder 5 First punch 6 Intermediate formed body 6a Body 6b Flange 6c Shoulder 7 Second die 7a Die Body 7b Die flange 7c Die shoulder 8 Second punch 8a Punch body 8b Punch flange 8c Punch shoulder PD Product depth PSR Product shoulder radius PBR Product bottom radius PCR1, PCR2, PCR3 Product corner radius DSR1 First die shoulder DSR2 Second die shoulder radius DD1 First die depth DD2 Second die depth PUSR1 First punch shoulder radius PUSR1 Second punch shoulder radius PUD1 Second punch depth PUD2 Second punch depth MSR Shoulder radius of intermediate compact MD Depth of intermediate compact

Claims (2)

A method for manufacturing a bottomed tubular part including a bottomed tubular main body and a flange portion extending from an opening of the main body, comprising:
a first step of obtaining an intermediate formed body from a plate material by drawing using a first die having a first die shoulder radius larger than a product shoulder radius, which is a radius of a connection portion between the main body and the flange portion, and a first die depth deeper than a product depth, which is a depth of the main body;
a second step of obtaining the bottomed tubular part from the intermediate formed body by drawing using a second die having a second die shoulder radius equal to the product shoulder radius and a second die depth equal to the product depth,
A method for manufacturing a bottomed tubular part , wherein a corner radius of the bottomed square tubular shape is 20 mm or more, an initial plate thickness of the blank is 1.0 mm or more, and the first die depth satisfies the following formula .

The method for manufacturing a bottomed tubular part according to claim 1, wherein the plate material is made of aluminum.

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