JP7816068B2 - Press die and press molding method - Google Patents

Description

This disclosure relates to a press die and a press molding method.

Patent Document 1 describes a method for manufacturing a fuel cell separator. This manufacturing method involves a fuel cell separator that includes a gas flow path consisting of multiple concave and convex portions in a central region and flat portions around the gas flow path. At least one of the flat portions on both sides of the gas flow path has first bends that bend approximately perpendicularly in the same direction on both edges. The inner flat portions of both first bends have second bends between the gas flow path-side flat portion and the edge-side flat portion, and the cross-sectional shape of the bent end on the gas flow path side of the second bend forms a smooth curve.

International Publication No. 2017/085868

When manufacturing thin plate workpieces with uneven surfaces, such as fuel cell separators, one technique is to provide ribs on the workpiece as a countermeasure against warping due to springback. In the manufacturing method described in Patent Document 1, warping is prevented by providing the above-mentioned first and second bends on both ends of the workpiece when manufacturing fuel cell separators.

However, even if ribs are provided on the workpiece to form a plate-shaped part, the amount of warping may vary depending on the material properties and rolling direction of the workpiece. Therefore, there is a need to develop technology that can easily adjust the variation in warping of plate-shaped parts.

This disclosure has been made to solve these problems, and its purpose is to provide a press die and press molding method that can easily adjust the warpage variation of plate-shaped parts.

The press die according to the present disclosure comprises a punch for providing ribs on a plate-shaped part to be pressed, a slide block that slides on the surface of the punch opposite the surface that abuts against the plate-shaped part, and a ball screw that slides the slide block, and the surface where the punch and slide block contact is inclined with respect to the axial direction of the ball screw. Because the press die is configured to adjust the height of the punch by moving the slide block, i.e., the height of the rib, it is possible to easily adjust variations in warpage of the plate-shaped part.

The press forming method disclosed herein includes a rib forming step in which the rib is press-formed into the plate-shaped part using a press die including a punch for providing a rib on the plate-shaped part to be pressed, a slide block that slides on the surface of the punch opposite the surface that abuts the plate-shaped part, and a ball screw that slides the slide block, where the surface where the punch and slide block contact is inclined with respect to the axial direction of the ball screw. Because the press forming method uses a press die configured to adjust the height of the punch by moving the slide block, i.e., configured to adjust the height of the rib, it is possible to easily adjust variations in warpage of the plate-shaped part.

This disclosure provides a press die and press molding method that can easily adjust the warpage variation of plate-shaped parts.

FIG. 10 is a top view showing an example of a plate-shaped part manufactured using a press die according to a comparative example. 1 is a top view showing an example of a plate-shaped part manufactured using a press die according to an embodiment. FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a press die according to an embodiment. FIG. 4 is an enlarged schematic view of a portion of the press die of FIG. 3. 5 is a cross-sectional view showing an example of a contact portion between a slide block and a punch in a part of the press die of FIG. 4. FIG. FIG. 1 is a flow diagram illustrating an example of a press molding method using a press die according to an embodiment.

The present invention will be described below through embodiments of the invention, but the claimed invention is not limited to the following embodiments. Furthermore, not all of the configurations described in the embodiments are necessarily essential as means for solving the problem.

(Embodiment)
First, an example of a plate-shaped part manufactured using a press die according to a comparative example will be described with reference to Fig. 1. Fig. 1 is a top view showing an example of a plate-shaped part manufactured using a press die according to a comparative example.

The plate-shaped component 10p according to the comparative example shown in Figure 1 is a metal plate having protrusions 12 formed in the irregularity forming region 11 and ribs 13p formed on both ends of the plate-shaped component 10p that are located outside the irregularity forming region 11. The plate-shaped component 10p may be, for example, a fuel cell separator formed by pressing a single metal plate, with ribs 13p formed on the peripheral edge of the irregularity forming region 11, which serves as a gas flow path, etc.

In Figure 1, the cross-sectional view of plate-shaped part 10p taken from the A-A direction is shown as plate-shaped part 10A, and the cross-sectional view of plate-shaped part 10p taken from the B-B direction is shown as plate-shaped part 10B. As shown in plate-shaped part 10B, plate-shaped part 10p has an insufficient height Hb of rib 13p, and as shown in plate-shaped part 10A, the overall height WAa is large, resulting in significant warpage. In plate-shaped part 10p, providing rib 13p increases the rigidity of both ends and somewhat reduces warpage compared to a plate-shaped part without rib 13p. However, in plate-shaped part 10p, warpage caused by springback during the formation of the concave-convex shape is not fully suppressed, and warpage varies from product to product. Warpage due to springback is particularly pronounced in thin plate products with flow channels or concave-convex shapes formed from a material such as Ti that is approximately 0.1 mm thick, but this example is not limited to this.

Since variations in warpage such as this can occur due to variations in material properties and plate thickness, it is necessary to adjust the rib height to an optimum state. For example, the rib height can be adjusted by adjusting the punch height and the thickness of a shim plate, but this requires molding once, checking the product quality, removing the product from the press, disassembling the mold, adjusting the punch, reassembling, and molding again, which takes a lot of time and may not be possible to complete in one go. In particular, since the punch is fixed inside the mold, the mold must be disassembled once to make the adjustments described above.

In contrast, in this embodiment, by using a press die as described below with reference to Figures 3 to 5, it is possible to easily adjust the warpage variation of a plate-shaped part without requiring such effort. Before describing the press die according to this embodiment, a plate-shaped part 10 manufactured using this adjustment will be described with reference to Figure 2. Figure 2 is a top view showing an example of a plate-shaped part manufactured using the press die according to this embodiment.

The plate-shaped component 10 manufactured using the press die according to this embodiment, as illustrated in Figure 2, is a metal plate having protrusions 12 formed in the irregularity forming region 11 and ribs 13 formed on both ends of the plate-shaped component 10p that are located outside the irregularity forming region 11. The plate-shaped component 10 can be, for example, a fuel cell separator formed by pressing a single metal plate, with ribs 13 formed on the peripheral edge of the irregularity forming region 11, which serves as a gas flow path, etc.

2, the cross-sectional view of plate-shaped part 10 viewed from the CC direction is shown as plate-shaped part 10C, and the cross-sectional view of plate-shaped part 10 viewed from the DD direction is shown as plate-shaped part 10D. In this embodiment, ribs 13 are press-formed after adjusting the height Hd of ribs 13 as shown in plate-shaped part 10D and the overall height WAc as shown in plate-shaped part 10C to reduce warpage. In plate-shaped part 10, ribs 13 with adjusted heights can increase the rigidity of both ends and reduce warpage. Therefore, even if plate-shaped part 10 is molded from a thin material such as Ti with a thickness of approximately 0.1 mm and is a thin plate product or a thin film product with flow channels or uneven shapes, warpage due to springback can be reduced. Furthermore, because adjustments can be made for each molded product, warpage variation can also be reduced.

Next, an example configuration of a press die according to this embodiment will be described with reference to Figures 3 to 5. Figure 3 is a schematic cross-sectional view showing an example configuration of a press die according to this embodiment. Figure 4 is a schematic enlarged view of a portion of the press die in Figure 3 (mainly the portion surrounded by the dashed line), and Figure 5 is a cross-sectional view showing an example of the contact portion between the slide block and punch in the portion of the press die in Figure 4. Note that for convenience, hatching indicating cross sections has been omitted in Figure 4.

As shown in Figure 3, the press die 20 according to this embodiment can include legs 21, a lower die 22, a support 23, an upper die housing 24, a ball screw 25, a material holding member 26, slide blocks 28a and 28b, and a punch 29. The press die 20 can also be referred to as a press machine. Note that while the press die 20 will be described as being used to manufacture the plate-shaped part 10 shown in Figure 2 as a product, it can also be configured to be used to manufacture plate-shaped parts of other shapes, including their thickness.

The lower die 22 is the lower die on which the plate-shaped part 10 to be pressed (hereinafter also referred to as the workpiece W) is placed, and can be supported by the legs 21. The support portion 23 supports the punch 29 and the screw shaft 27 of the ball screw 25, and together with these, the ball screw 25 allows for vertical movement relative to the upper die housing 24. The support portion 23 can also be provided with a hole to allow the screw shaft 27 to rotate, and can also be provided with a bearing or the like to rotatably support the screw shaft 27. The support portion 23 or the upper die housing 24 can also be configured to support the material holding member 26 so that it can move up and down.

The upper housing 24 is an upper housing supported by the legs 21. A portion of the ball screw 25 is fixed to the upper housing 24. The ball screw 25 can be equipped with a mechanism for changing its length in the vertical direction, such as a pressure cylinder, thereby allowing the support part 23 to move up and down relative to the upper housing 24. The ball screw 25 can also include a mechanism on its lower side that allows the screw shaft 27 to rotate. This mechanism can be equipped with, for example, a motor 30 for rotating the screw shaft 27 and a drive circuit for driving the motor 30.

As shown in Figure 4, the material holding member 26 is a member that holds the workpiece W against the lower die 22, for example, from both ends. The screw shaft 27 has a shaft rotatably attached to the ball screw 25, and is threaded (formed) on the shaft, with threads 27a and 27b formed in different directions on the left and right as shown in Figure 4. The screw shaft 27 is provided to slide the slide blocks 28a and 28b in opposite directions.

Slide blocks 28a and 28b each have a nut portion that threads onto threads 27a and 27b of screw shaft 27, and are movable in opposite directions along the shaft direction of screw shaft 27 by rotating screw shaft 27 on ball screw 25. In particular, slide blocks 28a and 28b are components that slide along the surface of punch 29 opposite the surface that abuts against the workpiece W. While it is possible to provide only one slide block, it is recommended to provide two or more, preferably an even number, along the shaft direction of screw shaft 27 in order to accurately move punch 29 up and down.

The punch 29 is used to create ribs 13 on the workpiece W to be pressed. As shown in Figure 2, the ribs 13 are generally provided at both ends of the plate-shaped part 10 for the purpose of suppressing warpage. A punch 29 with a corresponding shape is also provided at a corresponding position, and a corresponding lower die 22 is also prepared. However, the ribs 13 are not limited to this example and may be provided only at one end of the plate-shaped part 10, on all four sides, or in the center.

The upper surface of the punch 29 can be composed of a parallel surface 29s parallel to the ground and contact surfaces 29sa and 29sb inclined from the parallel surface 29s. However, the upper surface of the punch 29 does not necessarily have to have a parallel surface 29s.

As shown by the example of the surfaces of abutment surfaces 29sa and 29sb facing the punch 29, the surfaces where the punch 29 and slide blocks 28a and 28b come into contact are inclined with respect to the axial direction (shaft direction) of the screw shaft 27. As a result, by moving slide blocks 28a and 28b in opposite directions in the shaft direction of the screw shaft 27, the punch 29 can be moved upward or downward. In this example, moving slide block 28a to the right and slide block 28b to the left lowers the punch 29, and moving them in the opposite direction raises the punch 29.

In this state, the press die 20 adjusts the vertical position of the punch 29 by rotating the screw shaft 27, and then the punch 29, together with the support part 23, is lowered toward the lower die 22 by the pressure cylinder of the ball screw 25, etc., to perform press forming. As the lower die 22 is the lower die on which the workpiece W is placed, as described above, it is sufficient that the maximum depth is dug in accordance with the amount of vertical movement of the punch 29.

Furthermore, if the contact surface between the punch 29 and the slide blocks 28a, 28b is inclined toward the side where the workpiece W is placed, i.e., toward the lower die 22, with respect to the shaft direction of the screw shaft 27, even a punch 29 with a simple shape such as that shown in Figures 3 and 4 can be moved upward or downward depending on the direction of rotation of the screw shaft 27.

In the example of Figure 3, the screw shaft 27 is depicted overlapping the top of the punch 29. Two sets of screw shaft 27 and slide blocks 28a, 28b can be provided, sandwiching the punch 29 vertically in the plane of Figure 3. Also, a set of screw shaft 27 and slide blocks 28a, 28b and a punch 29 can be provided for each rib 13 to be formed.

As described above, according to this embodiment, the press die 20 is configured to be able to adjust the height of the punch 29 by moving the slide blocks 28a and 28b, i.e., the height of the rib 13, making it possible to easily adjust the variation in warpage of the plate-shaped part 10 based on material properties, etc.

The effect will be explained using a specific example. For example, when press-forming a thin plate part with an uneven surface, springback during the uneven forming process can cause warpage throughout the entire thin plate part. While the amount of warpage can be reduced by setting the rib height, the amount of warpage can vary depending on the rolling direction of the material, its elongation, and other characteristics. This necessitates adjusting the height of the punch used for rib formation. Disassembling the die, adjusting the shims, and reassembling it for this adjustment takes a lot of time. However, this embodiment is equipped with a movable punch mechanism that can adjust the height of the rib-forming punch 29 within the press die 20 (press machine). This movable punch mechanism rotates the shaft of the screw shaft 27 of the ball screw 25 and moves the inclined slide blocks 28a and 28b left and right depending on the amount of warpage. This changes the height of the punch 29 and the forming height of the rib, thereby adjusting the amount of warpage in the product.

The press die 20 may also be provided with a control unit (not shown) in the portion shown in Figure 3 or external to the portion shown in Figure 3. This control unit is a component that controls the rotation of the screw shaft 27 to adjust the height of the rib 13 to be provided, and in the example of Figure 3, it may be included in the ball screw 25 or may be a component that controls the ball screw 25.

The control unit can be realized, for example, by an integrated circuit, and can be realized by a processor such as an MPU (Micro Processor Unit) or CPU (Central Processing Unit), work memory, and non-volatile storage device. A control program executed by the processor is stored in this storage device, and the processor reads the program into the work memory and executes it, thereby controlling the rotation of the screw shaft 27. The program is for controlling the rotation of the screw shaft 27. The control unit can also be configured by incorporating the program into a general-purpose computer in an executable manner.

The press die 20 can also be equipped with a measuring device (not shown), such as a laser displacement meter, for measuring the warpage of the workpiece W. Note that the measuring device is not limited to a laser-type measuring device. For example, the measuring device can be provided on the underside of the material holding member 26. By providing a mechanism for moving the material holding member 26 upward, the material holding member 26 can be moved upward by this mechanism during measurement, allowing the measuring device to measure the warpage. However, the placement of the measuring device is not limited to this, and any arrangement that allows for warpage measurement can be used. The control unit can then control the rotation of the screw shaft 27 based on the warpage measured by the measuring device.

Furthermore, as illustrated in Figure 5, the opposite surface of the punch 29 and the surfaces of the slide blocks 28a and 28b that contact the opposite surfaces can be provided with engagement portions 28e and 29e that engage with each other to allow the punch 29 and the slide blocks 28a and 28b to slide. By engaging the engagement portion 28e on the slide blocks 28a and 28b with the engagement portion 29e on the punch 29, the punch 29 can be slid accurately in the desired direction.

Next, we will explain the press forming method (press processing method) according to this embodiment. This press forming method includes a rib forming process in which a press die 20 is used to press-form ribs 13 into the workpiece W. As described above, this press forming method uses a press die 20 that is configured to adjust the height of the punch 29 by moving the slide blocks 28a, 28b, i.e., a configuration in which the height of the rib 13 can be adjusted. This makes it possible to easily adjust variations in warpage of the plate-shaped part 10.

A specific example will be described with reference to Figure 6. Figure 6 is a flow diagram illustrating an example of a press molding method using the press die 20 according to this embodiment.

First, a rib-less workpiece is formed using a press die (hereinafter, the second press die) different from press die 20 (step S1). This allows, for example, the unevenness-forming region 11 including the convex portion 12 in Figure 2 to be formed in the workpiece. The warpage of the workpiece is measured using a measuring device provided on the second press die or a measuring device provided on press die 20, and the measured warpage is recorded in the internal memory of the control unit of press die 20 (step S2). The control unit determines whether the recorded warpage is within the allowable range (step S3). If it is not within the allowable range, the workpiece is discarded as an NG workpiece so that it cannot be used as a product (step S8), and the process ends. The allowable range used for the determination in step S3 can be determined arbitrarily, but a threshold value can be used to determine whether significant warpage will occur that cannot be adjusted even by press die 20.

On the other hand, if the answer is YES in step S3, the control unit calculates the height of the punch 29 based on the recorded warpage so that the rib 13 is formed so that the workpiece does not warp or the warpage of the workpiece is within the acceptable range for the product, and adjusts the settings so that it lowers to that height (step S4).The control unit then forms the rib 13 in the workpiece using the press die 20, which is set so that the punch 29 lowers to the adjusted height (step S5).

Next, the control unit controls the measuring device to measure the warpage of the workpiece and records the result in the control unit's internal memory (step S6), and determines whether the recorded warpage is within the acceptable range for the product (step S7). If the answer is YES in step S7, the manufactured plate-shaped part 10 is acceptable as a product, and the process ends. On the other hand, if the answer is NO in step S7, the process returns to step S4, and steps S4 to S6 are repeated until step S7 returns YES. However, for example, if the answer is NO in step S7, or if step S7 is judged NO a predetermined number of times, the workpiece can be discarded as a non-rejected product, taking into account factors such as insufficient strength due to repeated press molding, as in the procedure of step S8.

In Figure 6 above, an example was given in which a workpiece without ribs was formed in step S1 using a press die different from press die 20. However, as an alternative method, if press die 20 is equipped with a punch for forming the unevenness forming region 11 including the convex portion 12 and punch 29 is kept out of contact with the workpiece, a workpiece without ribs can be formed in the first stroke in step S1 using press die 20. In that case, in step S5, ribs 13 can be formed in the second stroke using press die 20.

As another alternative method, a press die 20 equipped with a punch 29 and a punch for forming the unevenness forming region 11 can be used from the very beginning to form a workpiece with a rib 13 to suppress warpage. In this case, the height of the punch 29 can be determined from warpage information previously recorded for the same product. The control unit then controls the measuring device to measure the warpage of the workpiece and records this in the control unit's internal memory for future reference. If the recorded warpage is within the acceptable range for a product, a decision is made to treat the workpiece as a product, and if it is not within the acceptable range, a decision is made to discard the workpiece as an NG product.

Furthermore, in the method described above in which rib forming is repeated, the ribs formed after adjustment can be larger than the ribs formed initially. In this case, the size of the rib can be kept small at the time of initial forming. Furthermore, from the perspective of the strength of the finished product, ribs can be formed in other positions instead of repeatedly press-forming in the same position. In this case, a set of punches 29 and other components for forming ribs in the other positions will be provided in the press die 20. Of course, if the product design makes it difficult to form many ribs, it is best to form ribs in the same position. Note that this type of rib re-forming can be eliminated by switching the target workpiece.

As described above, the press forming method according to this embodiment can include a warpage acquisition process and an adjustment process. Here, the warpage acquisition process is a process of acquiring the results of measuring the warpage that has occurred in the direction of rib formation on the workpiece W before the rib forming process is performed, or the results of measuring the warpage that has occurred in the direction of the rib on the workpiece W after the rib forming process is performed. The adjustment process is a process of adjusting the height of the ribs to be provided on the workpiece W in the rib forming process based on the results acquired in the warpage acquisition process.

(Alternative examples, etc.)
In the above embodiment, only one example of the shape of the punch, plate-shaped part, etc. in the press die has been described. However, any shape of punch or plate-shaped part, in other words, any shape of rib can be formed on any shape of plate-shaped part, as long as it is press-formable. For example, the protrusion 12 can be used for forming a flow path, for heat dissipation, or for aligning with other parts, but protrusions, recesses, holes, etc. used for other purposes may instead be formed. Of course, the plate-shaped part to be manufactured may not have an uneven region such as the uneven region 11. Furthermore, while the plate-shaped part 10 can be a metal plate, it is not limited thereto. Any material that can be press-formed, such as a resin plate, may be used, and the plate-shaped part 10 may have any thickness.

The present invention is not limited to the above-described embodiment, and modifications can be made as appropriate without departing from the spirit of the invention.

10...plate-shaped part, 10p...plate-shaped part according to comparative example, 11...concave-convex forming area, 12...protruding portion, 13...rib, 13p...rib according to comparative example, 20...press die, 21...leg portion, 22...lower die, 23...support portion, 24...upper die housing, 25...ball screw, 26...material holding member, 27...screw shaft, 28a, 28b...slide block, 29...punch, 29s...parallel surface, 29sa, 29sb...contact surface, 30...motor.

Claims (5)

a punch for providing a rib on a plate-shaped part to be pressed;
a slide block that slides on a surface of the punch opposite to a surface that contacts the plate-like part;
a ball screw for sliding the slide block;
a control unit that controls the rotation of the ball screw in order to adjust the height of the rib to be provided;
a measuring instrument for measuring the warpage of the plate-shaped component;
Equipped with
a surface where the punch and the slide block come into contact is inclined with respect to an axial direction of the ball screw;
the control unit adjusts the height of the rib by controlling the rotation of the ball screw based on the warpage measured by the measuring instrument.
Press mold. the control unit determines whether the warpage measured by the measuring instrument is within a predetermined tolerance range, and repeatedly adjusts the height of the rib by controlling the rotation of the ball screw until the warpage falls within the predetermined tolerance range.
The press die according to claim 1 . a rib forming process in which the rib is press-formed into the plate-like part using a press die including a punch for providing a rib on the plate-like part to be pressed, a slide block that slides on a surface of the punch opposite to a surface that abuts against the plate-like part, and a ball screw that slides the slide block, wherein the surface where the punch and the slide block come into contact is inclined with respect to the axial direction of the ball screw ;
a warpage acquisition process for acquiring a result of measuring a warpage occurring in the direction of forming the rib of the plate-shaped part before the rib forming process is performed, or a result of measuring a warpage occurring in the direction of the rib of the plate-shaped part after the rib forming process is performed;
an adjusting step of adjusting the height of the rib provided on the plate-like component by controlling the rotation of the ball screw in the rib forming step based on the results obtained in the warpage obtaining step;
Including,
Press forming method. The warpage acquisition process includes a first acquisition process of acquiring a result of measuring the warpage occurring in the direction of forming the rib of the plate-like part before the rib forming process is performed, a second acquisition process of acquiring a result of measuring the warpage occurring in the direction of the rib of the plate-like part after the rib forming process is performed, and a determination process of determining whether the measurement result of the warpage acquired in the second acquisition process is within a predetermined tolerance range,
the adjusting step repeats adjusting the height of the rib until it is determined in the determining step that the measurement result of the warp falls within the predetermined tolerance range, and stops adjusting the height of the rib when it is determined in the determining step that the measurement result of the warp falls within the predetermined tolerance range.
The press molding method according to claim 3 . The warpage acquisition process includes an acquisition process of performing the rib forming process and acquiring a result of measuring the warpage occurring in the direction of the rib of the plate-like part, and a determination process of determining whether the measurement result of the warpage acquired in the acquisition process is within a predetermined tolerance range,
the adjusting step repeats adjusting the height of the rib until it is determined in the determining step that the measurement result of the warp falls within the predetermined tolerance range, and stops adjusting the height of the rib when it is determined in the determining step that the measurement result of the warp falls within the predetermined tolerance range.
The press molding method according to claim 3.