Method for manufacturing press-formed articles, and tray and hot-press production line used for the same

Abstract

The manufacturing method of the press-formed product has a heating step, a conveying step, and a pressing step. In the heating step, the first workpiece (W1) is placed on the first pillar group (3) extending upward from the tray main body (2), the second workpiece (W2) is placed on the second pillar group (3) and is arranged in an overlapping manner above the first workpiece (W1), and heating is performed in the above state. In the conveying step, the second workpiece (W2) is arranged in an overlapping manner above the first workpiece (W1), and the tray main body (2) is conveyed together from the heating device (14) to a lifting position. Further, in the lifting position, the second workpiece (W2) is lifted upward by the conveying device (46), the first workpiece (W1) is lifted by the conveying device (46), and each is conveyed to a pressing position.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a pressed and shaped article including heating, conveying and pressing processes, as well as a tray and hot pressing production line used in manufacturing the pressed and shaped article. Background Technology

[0002] Traditionally, a technique has been used to press raw materials heated to a predetermined temperature using a press. For example, in hot pressing, a hot-pressing steel sheet is heated to the austenitic region (approximately 900°C or higher) and hot-pressed. Following forming and quenching, pressed products with strengths of, for example, 1500 MPa or higher can be obtained. In typical hot pressing, quenching is performed by rapid cooling through heat transfer in contact with the die during pressing. Therefore, to achieve a sufficient quenching effect, the temperature of the raw material at the start of pressing, approximately equivalent to the quenching start temperature, needs to be maintained above a predetermined temperature. In this case, the predetermined temperature at the start of pressing varies depending on the raw material, but is, for example, 700°C or higher.

[0003] Japanese Patent Nos. 5910305 and 5910306 disclose a hot pressing forming method comprising the following steps: heating multiple overlapping conductive plate-shaped workpieces by mounting electrodes on them and energizing them; placing the heated plate-shaped workpieces in predetermined pressing positions different from the energized positions; and pressing the plate-shaped workpieces in the pressing positions into shape. By simultaneously heating multiple plate-shaped workpieces by energizing them, productivity is improved.

[0004] In the aforementioned prior art, heat dissipation occurs during workpiece transport, causing the workpiece temperature to drop. As a result, there is a concern that the required workpiece temperature cannot be maintained when it is fed into the die of the press, making it impossible to adequately quench the pressed product.

[0005] Therefore, Japanese Patent No. 5814669 discloses a hot pressing conveying device that holds and conveys a heated plate-shaped workpiece between different processes in a hot pressing production line. The hot pressing conveying device conveys the heated workpiece while covering it with an insulation cover. This maintains the workpiece at the temperature required for quenching during conveying.

[0006] Furthermore, the hot pressing apparatus disclosed in Japanese Patent No. 4673656, as a heating device for the workpiece, i.e., a metal sheet, includes a primary heating mechanism based on induction heating or electrostatic heating and a secondary heating mechanism based on radiative heat transfer. The secondary heating mechanism based on radiative heat transfer is arranged in the conveying device from the primary heating mechanism to the hot pressing die. Through secondary heating based on radiative heat transfer, the metal sheet can be heated uniformly, reducing temperature deviations in the metal sheet.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent No. 5910305

[0010] Patent Document 2: Japanese Patent No. 5910306

[0011] Patent Document 3: Japanese Patent No. 5814669

[0012] Patent Document 4: Japanese Patent No. 4673656 Summary of the Invention

[0013] The problem the invention aims to solve

[0014] The inventors noted that when hot-pressing raw materials to a thinner thickness, the temperature drop during transport to the press after heating the raw materials can affect the quality of the pressed product. Therefore, methods to suppress the temperature drop of the raw materials during transport were investigated. The research revealed that, as with the prior art, simply covering the raw materials with an insulation cover during transport is insufficient to adequately suppress the temperature drop. Furthermore, a secondary heating mechanism for heating the raw materials during transport was considered. However, this would require adding equipment along the transport path, including a heat source for the secondary heating mechanism. This could lead to increased equipment size and higher equipment and operating costs.

[0015] Therefore, this application discloses a method for manufacturing a pressed molded article and a tray, which can easily mitigate the temperature drop of the raw material during the conveying time from the heating of the raw material to the start of pressing in hot pressing.

[0016] Solution for solving the problem

[0017] The manufacturing method of the pressed molded article according to the technical solution of the present invention includes: a heating step, in which a plate-shaped first workpiece and a plate-shaped second workpiece are simultaneously heated; a conveying step, in which the first workpiece and the second workpiece, which have been heated in the heating step, are conveyed to a press; and a pressing step, in which the first workpiece and the second workpiece conveyed to the press are processed using the press. In the heating step, the first workpiece is placed on a first support group of at least three supports extending upward from a tray body having a hollow portion that runs vertically through when viewed from above; the second workpiece is placed on a second support group of at least three supports extending upward from the tray body; and the second workpiece is arranged above the first workpiece, overlapping the first workpiece in the normal direction of the plate surface of the first workpiece. In this state, heating is performed using a heating device.

[0018] The conveying process includes a first conveying process and a second conveying process. In the first conveying process, the first workpiece is placed on the first support group, and the second workpiece is placed on the second support group, above the first workpiece. The second workpiece is arranged overlapping the first workpiece in the normal direction of the first workpiece's surface. In this state, it is conveyed from the heating device to the lifted position along with the tray body. In the second conveying process, at the lifted position, the second workpiece placed on the second support group is lifted upward by the conveying device and conveyed to the pressing position of the second workpiece. At the lifted position, the first workpiece placed on the first support group is lifted upward by the conveying device and conveyed to the pressing position of the first workpiece.

[0019] The effects of the invention

[0020] According to this disclosure, during the conveying time from the heating of the raw material to the start of pressing in hot pressing, the temperature drop of the raw material can be easily mitigated. Attached Figure Description

[0021] Figure 1 This is a schematic diagram showing the hot pressing production line of this embodiment.

[0022] Figure 2 This is a top view of the tray in this embodiment as seen from above.

[0023] Figure 3 Observing from the direction of arrow F Figure 2 The side view obtained from the tray shown.

[0024] Figure 4 This is a top view showing another example of the configuration of the first and second support groups.

[0025] Figure 5 Observing from the direction of arrow F Figure 4 The side view obtained from the tray shown.

[0026] Figure 6 This is a side view showing an example of a support group where the first and second workpieces are not flat.

[0027] Figure 7 This is a side view showing an example of a support group where the first and second workpieces are not flat.

[0028] Figure 8 This is a top view showing an example of a tray where the areas of the first workpiece W1 and the second workpiece W2, as viewed from above, are different.

[0029] Figure 9 Observing from the direction of arrow F Figure 8 The side view obtained from the tray shown.

[0030] Figure 10 This is a side view showing an example where the first and second workpieces are plates with different thicknesses.

[0031] Figure 11 This is a top view showing a structural example of a tray equipped with a shielding panel.

[0032] Figure 12 Observing from the direction of arrow F Figure 11 The side view obtained from the tray shown.

[0033] Figure 13 This is a diagram illustrating a modified example of the hot pressing production line of this embodiment.

[0034] Figure 14A It means Figure 13 A diagram showing the structure of the conveying device.

[0035] Figure 14B It means Figure 14A The diagram shows the first arm of the conveyor device in the open state.

[0036] Figure 15 This indicates the location of the temperature measurement in the experimental example.

[0037] Figure 16 It is a graph showing the average cooling rate as a result of the measurement.

[0038] Figure 17 It is a graph representing the range of objects derived as the average cooling rate. Detailed Implementation

[0039] In hot pressing, the initial temperature at the start of pressing depends on the heating temperature of the raw material and the temperature drop during the time it takes for the raw material to be conveyed to the pressing die after heating. The heating temperature of the raw material depends on the metallurgical conditions. Furthermore, the conveying time from heating to delivery to the die depends on the equipment structure and specifications. The amount of temperature drop during this conveying period depends on the heat capacity of the raw material. For example, in the case of steel plates, heat is mainly dissipated through heat transfer from the surface and back to the atmosphere and through thermal radiation. The inventors have noted that the amount of temperature drop during conveying is largely dependent on the thickness of the raw material. That is, as mentioned above, when the thickness of the raw material decreases, even with the same conveying time, the temperature drop is greater, making it sometimes difficult to ensure the forming start temperature required for quenching. As a result, it is possible that the required part strength for the pressed product cannot be obtained.

[0040] The inventors have researched a method for suppressing temperature drop during transport without the need for an additional heat source. When a plate-shaped raw material (workpiece) is heated using a heating device, the workpiece is transported from the heating device to a position where it is lifted by a conveying device via a conveying path such as rollers. The workpiece is then lifted by the conveying device and placed in the pressing position of a press. The inventors focused on the state of the workpiece from the heating device to its lifting by the conveying device and researched methods for suppressing temperature drop during this transport process.

[0041] The in-depth research resulted in the following approach: Multiple (e.g., two) plate-shaped workpieces are arranged on a tray in an overlapping manner, heated by a heating device, and then removed from the heating device along with the tray while maintaining their overlapping state. During transport after heating, the multiple facing workpieces are subjected to mutual radiative heat, thus compensating for each other's heat. Furthermore, in addition to radiative heat, heat also moves from the workpieces to the surrounding air through heat transfer. For example, when multiple workpieces are arranged in a state of contact and overlapping in a direction perpendicular to the workpiece's surface, the contact portions do not come into contact with the air, thus reducing the heat transfer from the workpieces to the air. Additionally, if multiple workpieces are arranged at intervals overlapping in a direction perpendicular to the workpiece's surface, the air heated by heat transfer from the multiple workpieces remains trapped in the space between them. This trapped heated air exists between the multiple workpieces, thereby reducing the temperature difference between the air between the multiple workpieces and between the multiple workpieces themselves. Therefore, the heat transfer from the workpieces to the air is reduced, achieving a heat preservation effect. Therefore, it is possible to mitigate the temperature drop of multiple workpieces during transport. The following implementation is based on this insight.

[0042] The method for manufacturing a pressed molded article according to an embodiment of the present invention includes: a heating step in which a plate-shaped first workpiece and a plate-shaped second workpiece are simultaneously heated; a conveying step in which the heated first workpiece and the second workpiece are conveyed to a press; and a pressing step in which the first workpiece and the second workpiece conveyed to the press are processed using the press. In the heating step, the first workpiece is placed on a first support group of at least three supports extending upward from a tray body having a hollow portion extending vertically when viewed from above; the second workpiece is placed on a second support group of at least three supports extending upward from the tray body; and the second workpiece is arranged above the first workpiece, overlapping the first workpiece in the normal direction of the plate surface of the first workpiece. In this state, heating is performed using a heating device.

[0043] The conveying process includes a first conveying process and a second conveying process. In the first conveying process, the first workpiece is placed on the first support group, and the second workpiece is placed on the second support group, above the first workpiece. The second workpiece is arranged overlapping the first workpiece in the normal direction of the first workpiece's surface. In this state, it is conveyed from the heating device to the lifted position along with the tray body. In the second conveying process, at the lifted position, the second workpiece placed on the second support group is lifted upward by the conveying device and conveyed to the pressing position of the second workpiece. At the lifted position, the first workpiece placed on the first support group is lifted upward by the conveying device and conveyed to the pressing position of the first workpiece.

[0044] In the above-described manufacturing method, the first and second workpieces are heated in an overlapping state using the support assembly of the tray in the heating device. After heating, the first and second workpieces, along with the tray, are conveyed from the heating device to a lifted position. Therefore, from the heating device until they are lifted by the conveying device, the first and second workpieces are in an overlapping state. That is, the first and second workpieces overlap in a direction perpendicular to the surface of the first workpiece (normal direction). For example, the upper surface of the first workpiece and the lower surface of the second workpiece are opposite each other. Thus, from the end of heating until they are lifted by the conveying device, the multiple workpieces are subjected to mutual radiant heat, thereby compensating for each other's heat. In addition, for example, when the multiple workpieces are arranged to overlap at intervals, the air heated by heat transfer from the workpieces is retained in the space between the multiple workpieces. This provides a heat preservation effect. Furthermore, the first workpiece is placed on the first support assembly, and the second workpiece is placed on the second support assembly above it. The support assembly is formed to extend upward from the tray body. Therefore, when lifting the second and first workpieces placed on the support assembly using the conveyor, the support assembly will not become an obstacle. The lifting action can be performed simply and quickly. As a result, during the conveying time in hot pressing, from the time the raw material is heated until the pressing begins, the temperature drop of the raw material can be easily mitigated.

[0045] The tray body can also be configured such that, when viewed from above, the hollow area is wider than the constituent components of the tray body. This facilitates heat transfer from below the tray body to the first and second workpieces during the heating process. Alternatively, when viewed from above, the first and second support groups can be located between the hollow areas of the tray body. This facilitates heat transfer from below the tray body through the hollow areas surrounding the first and second support groups to the first workpiece placed in the first support group and the second workpiece placed in the second support group.

[0046] The first and second plate-shaped workpieces are not limited to flat plates. At least one of the first and second plate-shaped workpieces may be, for example, a plate with a protrusion protruding in the normal direction of the plate surface, a plate with a hollow portion penetrating the plate, or a curved plate. At least one of the first and second workpieces may also be, for example, an intermediate formed product formed or processed from a flat plate (blank).

[0047] In the first conveying step, it is preferable to convey the first workpiece, whose lower surface is supported by the first support group, and the second workpiece, whose lower surface is supported by the second support group, in a state where they overlap each other at intervals in the normal direction of the plate surface of the first workpiece. Thus, during conveying, the upper and lower surfaces of the first and second workpieces respectively come into contact with air. Therefore, compared to the case where the first and second workpieces are in contact with each other, the difference in conditions between the upper and lower surfaces during conveying is reduced. As a result, the quality difference between the upper and lower surfaces of the first and second workpieces can be suppressed.

[0048] Preferably, in the heating process and the first conveying process, the first workpiece placed on the first support group and the second workpiece placed on the second support group are arranged to overlap vertically with an interval of less than 100 mm. This ensures that the interval between the first and second workpieces during conveying on the pallet is appropriate, effectively suppressing temperature drop. If the interval between the workpieces is too wide, the proportion of heat radiation emitted from one workpiece in a direction inclined relative to the normal to the plate surface that does not reach the opposite workpiece increases at the ends of the heated first and second workpieces. As a result, there is a possibility that the effect of mitigating temperature drop cannot be sufficiently achieved. Furthermore, if the interval between the workpieces is too wide, the air heated by heat transfer from the two workpieces becomes difficult to retain between them, potentially resulting in insufficient heat preservation.

[0049] Preferably, in the heating process and the first conveying process, the maximum vertical distance D (mm) between the first workpiece placed in the first support group and the second workpiece placed in the second support group, and the minimum plate thickness t (mm) of the thinnest portion of the first workpiece and the second workpiece are related by the following formula. This effectively suppresses temperature drops in both the first and second workpieces during conveying.

[0050] D≤120t

[0051] Alternatively, the area of ​​the second workpiece's surface can be larger than the area of ​​the first workpiece's surface. In this case, it is preferable that, during the heating process and the first conveying process, the entire first workpiece placed in the first support group and the second workpiece placed in the second support group overlap vertically. This allows the entire first workpiece to receive radiant heat from the second workpiece. Therefore, it is easier to maintain a uniform temperature for the entire first workpiece. Furthermore, the second support group can be positioned on the portion of the second workpiece that does not overlap with the first workpiece. Here, the area of ​​the first workpiece's surface is defined as the area of ​​the first workpiece placed in the first support group when viewed from above. The area of ​​the second workpiece's surface is defined as the area of ​​the second workpiece placed in the second support group when viewed from above.

[0052] The thickness of the second workpiece can also be greater than that of the first workpiece. That is, the thicknesses of the first and second workpieces can also be different. Furthermore, in this case, the temperature drop of the thinner first workpiece is suppressed due to the radiant heat from the second workpiece, which has a larger heat capacity. Therefore, the temperature drop of the thinner first workpiece, which is prone to temperature drop, can be effectively suppressed. In particular, as described above, this effect is even more pronounced when the first workpiece and the second workpiece are transported in a state where they overlap vertically.

[0053] Preferably, in the heating process and the first conveying process, the minimum distance ΔW between the end of the second workpiece placed in the second support group and the end of the first workpiece placed in the first support group when viewed from above is 5 mm or more. This ensures that the second support group is positioned away from the first workpiece.

[0054] Preferably, in the heating process and the first conveying process, the maximum value of the distance ΔW between the end of the second workpiece placed in the second support group and the end of the first workpiece placed in the first support group when viewed from above is 30 mm or less. This prevents the area of ​​the second workpiece from receiving excessive radiant heat from the first workpiece, thereby ensuring a temperature drop suppression effect on the second workpiece.

[0055] Alternatively, in the first conveying step, the first workpiece placed in the first support group and the second workpiece placed in the second support group are conveyed with their front ends covered by a shielding plate in the conveying direction. Since the shielding plate prevents air from contacting the front end of the workpiece in the conveying direction, the temperature drop of the end face of the workpiece in the conveying direction can be mitigated, and the movement of trapped air between the two workpieces, heated by heat transfer from both workpieces, can be suppressed. As a result, a heat preservation effect can be maintained. Therefore, the temperature drop of the workpiece during conveying can be further suppressed.

[0056] Alternatively, the shielding plate may have an inclined surface that slopes towards the first and second workpieces as it approaches from the center towards the ends. As a result, air encountering the shielding plate flows away from the first and second workpieces along the inclined surface. Therefore, the effect of suppressing temperature drop of the workpieces during transport is improved.

[0057] Alternatively, at least one of the first workpiece placed in the first support group and the second workpiece placed in the second support group may have a long side direction and a short side direction. The shielding plate can cover the long side direction of both the first workpiece placed in the first support group and the second workpiece placed in the second support group during the first conveying process. By covering the long side direction with the shielding plate, the effect of suppressing temperature drop of the workpiece during conveying can be further improved.

[0058] Alternatively, the first workpiece and the second workpiece may be differentially thick plates comprising thick-walled and thin-walled portions. In this case, during the heating process and the first conveying process, the thick-walled portion of the first workpiece placed in the first support group and the thin-walled portion of the second workpiece placed in the second support group may overlap vertically. Thus, the thick-walled and thin-walled portions compensate for each other's heat, and as a whole, they can efficiently suppress temperature drop.

[0059] Alternatively, in the second conveying step described above, the conveying device simultaneously lifts the second workpiece placed in the second support group and the first workpiece placed in the first support group, and conveys the first and second workpieces from the lifted position to the pressing position in a state of overlap in the normal direction of the surface of the first workpiece. By lifting the first and second workpieces simultaneously, the lifting time can be shortened. Furthermore, the first and second workpieces are conveyed from the lifted position to the pressing position in an overlapping state. Therefore, the effect of suppressing temperature drop during conveying is further improved.

[0060] As an example, the second conveying process may include the following steps:

[0061] A pair of first arms, which are rotatably mounted on the base frame of the conveying device, are driven to support and lift the lower surfaces of the two ends of the first workpiece placed on the first support assembly using the claws of the pair of first arms.

[0062] A pair of second arms, which are rotatably mounted on the base of the conveying device, are driven using a system different from that of the pair of first arms. The claws of the pair of second arms are used to support and lift the lower surfaces of both ends of the second workpiece placed on the second support assembly.

[0063] The first workpiece, whose lower surfaces at both ends are supported by the claws of the pair of first arms of the conveying device, and the second workpiece, whose lower surfaces at both ends are supported by the claws of the pair of second arms, are conveyed in a state of overlapping each other in the normal direction of the plate surface of the first workpiece.

[0064] Drive the pair of first arms to lower the first workpiece supported by the pair of first arms to the pressing position of the press; and

[0065] The pair of second arms are driven using a system different from that of the pair of first arms, so that the second workpiece supported by the pair of second arms is lowered to the pressing position of the press.

[0066] Therefore, the second workpiece and the first workpiece can be lifted simultaneously, and the first and second workpieces can be conveyed from the lifted position to the pressing position in an overlapping state along the normal direction of the surface of the first workpiece. Furthermore, the conveying device is not limited to a structure that simultaneously lifts the second and first workpieces and conveys them in an overlapping state. For example, the conveying device may include a first conveying device for lifting and conveying the second workpiece and a second conveying device for lifting and conveying the first workpiece.

[0067] The tray in an embodiment of the present invention comprises: a tray body having a shape extending along a surface perpendicular to the vertical direction, including a hollow portion extending vertically through the tray body; and a support assembly extending upward from the tray body. The support assembly includes: a first support assembly of at least three supports configured to support the lower surface of a plate-shaped first workpiece; and a second support assembly of at least three supports configured to support the lower surface of a plate-shaped second workpiece located above the first workpiece supported by the first support assembly. The first support assembly is configured such that, when viewed from above, the virtual straight lines connecting the supports form at least one triangle. The second support assembly is positioned differently from the first support assembly when viewed from above, and is also configured such that, when viewed from above, the virtual straight lines connecting the supports form at least one triangle. Each support in the second support assembly is taller than the lowest support in the first support assembly.

[0068] According to the above structure, the first and second workpieces are supported on a tray in an overlapping state using the first and second support groups. For example, the first and second workpieces are supported on the tray with the upper surface of the first workpiece and the lower surface of the second workpiece facing each other. Therefore, the first and second workpieces can be heated using a heating device while they are supported on the tray in an overlapping state, and can be conveyed from the heating device to a lifting position in this state. Thus, from the end of heating until the lifting by the conveying device, the first and second workpieces are subjected to mutual radiant heat, thereby compensating for each other's heat. In addition, the support groups are formed extending upward from the tray body. Therefore, when the second and first workpieces placed on the support groups are lifted upward using the conveying device, the support groups will not become an obstacle. The lifting action can be performed simply and quickly. As a result, during the conveying time from the heating of the raw material to the start of pressing in hot pressing, the temperature drop of the raw material can be easily mitigated. That is, a heated conveying tray for hot-pressed raw materials can be provided, which can easily mitigate the temperature drop of raw materials during conveying time.

[0069] The support assembly can also be fixed relative to the pallet body. That is, the support assembly can be installed in a fixed state relative to the pallet body. This simplifies the pallet construction. Conversely, if, for example, the height of each support assembly relative to the pallet body is variable, a heat-resistant drive mechanism is required. In this case, the structure becomes more complex, and manufacturing costs increase.

[0070] Alternatively, the second support group may include at least three supports, each of which is a certain height ΔH higher than the at least three supports in the first support group. In this case, the second workpiece supported by the second support group can be positioned at a height ΔH higher than the first workpiece supported by the first support group.

[0071] Preferably, the specified height ΔH is the height obtained by adding 0mm to 100mm to the maximum thickness of the first workpiece. This ensures that the interval between the first and second workpieces, which are carried on a pallet during transport, is appropriately maintained, effectively suppressing temperature drop.

[0072] Alternatively, the pallet may also include a shielding plate that covers the height region between the height of the lowest and highest pillars in the first and second pillar groups from a direction perpendicular to the vertical direction. The shielding plate can be used to further suppress temperature drops in both the first and second workpieces during transport, which are carried on the pallet.

[0073] Alternatively, the shielding plate may have an inclined surface that slopes towards the first and second support groups as it approaches the ends from the center. This causes the air encountering the shielding plate to flow along the inclined surface away from the first and second workpieces during transport, carrying them on a pallet. Consequently, the effect of suppressing temperature drop in the first and second workpieces during transport is improved.

[0074] Alternatively, when viewed from above, the pallet body may have a long side direction and a short side direction. The shielding plate may also be configured to cover the long side direction of the pallet body when viewed from above. By using the shielding plate to cover the long side direction of the pallet body, the effect of suppressing temperature drop of the workpiece being transported on the pallet can be further improved.

[0075] The hot pressing production line in an embodiment of the present invention comprises: the tray; a heating device for heating the first workpiece and the second workpiece carried on the tray; a conveying path disposed between the heating device and a raised position of the first workpiece and the second workpiece, for conveying the tray from the heating device to the raised position; a conveying device for supporting and lifting the first workpiece and the second workpiece carried on the tray at the raised position; at least one press having at least two sets of paired dies; and a moving device for moving the conveying device between the raised position and a pressing position between the at least two sets of paired dies.

[0076] Alternatively, the conveying device may include: a base frame capable of lateral movement perpendicular to the vertical direction; a pair of first arms rotatably mounted on the base frame; a pair of second arms rotatably mounted on the base frame; a first drive unit for driving the first arms; and a second drive unit for driving the second arms.

[0077] The pair of first arms have: a pair of first bases arranged laterally on the base frame and extending from the base frame in a vertical direction; and a first claw extending laterally curved from the pair of first bases respectively.

[0078] The pair of second arms have: a pair of second bases arranged laterally on the base frame and extending from the base frame in a vertical direction; and second claws extending laterally curved from the pair of second bases respectively.

[0079] The first drive unit changes the lateral distance of the pair of first claws by rotating the pair of first arms relative to the base frame.

[0080] The second drive unit changes the lateral distance of the pair of second claws by rotating the pair of second arms relative to the base frame.

[0081] The first drive unit and the second drive unit are configured to independently control the rotation of the first arm and the rotation of the second arm, respectively.

[0082] The pair of first claws are configured to support the lower surfaces of the lateral ends of the first workpiece in a state in which they are brought close to each other in the lateral direction.

[0083] The pair of second claws are configured to support the lower surfaces of the lateral ends of the second workpiece in a state in which they are brought close to each other in the lateral direction.

[0084] The positions of the first pair of claws in the vertical direction and the positions of the second pair of claws in the vertical direction are different from each other.

[0085] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same or equivalent parts in the drawings will be labeled with the same reference numerals, and their descriptions will not be repeated. The dimensional ratios between the constituent components shown in the figures do not necessarily represent actual dimensional ratios.

[0086] [Example of device structure]

[0087] Figure 1This is a schematic diagram showing the hot pressing production line 10 of this embodiment. The hot pressing production line 10 includes a heating device 14, a conveyor table 16, a manipulator 44, a conveying device 46, a press 20, and a controller 22. The conveyor table 16 is disposed near the outlet 14A of the heating device 14. The conveyor table 16 is disposed between the heating device 14 and the press 20.

[0088] Inside the heating device 14, multiple workpieces W1 and W2 are supported on a pallet 1 in an overlapping manner. After being heated by the heating device 14, the multiple workpieces W1 and W2 on the pallet 1 exit the heating device 14 together with the pallet 1. The pallet 1 carrying the multiple workpieces W1 and W2 exits the heating device 14 and is conveyed on the conveyor table 16 to a position where it is lifted by the conveyor device 46.

[0089] (Heating device)

[0090] The heating device 14 is a device for heating an object to be heated. Examples of heating devices 14 include resistance heating furnaces, gas heating furnaces, far-infrared heating furnaces, and near-infrared heating furnaces. The heating device 14 is not limited to a heating furnace; for example, it may be a high-frequency induction heating device, a low-frequency induction heating device, or an electrically powered heating device that directly heats the object to be heated by energizing it. The heating device 14 may also have a heating chamber. In the heating device 14, multiple indoor rollers 13 driven to rotate by a drive mechanism (not shown) may be provided inside the heating chamber. By rotating the indoor rollers 13, the objects to be heated (i.e., workpieces W1 and W2) on the indoor rollers 13 are conveyed. The outlet 14A and inlet 14B of the heating device 14 are provided in front of and behind the objects to be heated in the conveying direction within the heating chamber.

[0091] (Conveyor Platform)

[0092] The conveyor table 16 has multiple conveyor rollers 26 that are driven to rotate by a drive mechanism (not shown). Each conveyor roller 26 rotates synchronously with the inner roller 13, thereby enabling the conveying of objects between the conveyor table 16 and the heating chamber of the heating device 14. The multiple conveyor rollers 26 are arranged at intervals. The conveyor table 16 is an example of a conveying path that conveys a tray 1 containing a first workpiece W1 and a second workpiece W2 to be heated from the heating device 14 to a raised position. A raised position is provided on the conveyor table 16 where the workpiece is raised by the conveying device 46. Furthermore, the structure of the conveying path is not limited to... Figure 1 The conveyor platform 16 is shown. For example, the conveying path could also be a conveyor belt or track, etc. Additionally, in Figure 1 In the example shown, the lifting position is located on the conveyor path, but the lifting position may not be located on the conveyor path. Alternatively, the lifting position may be located independently of the conveyor path at a platform or similar facility at the conveyor destination.

[0093] (Press machine)

[0094] The press 20 includes a lower die 23 and an upper die 21 for pressing and forming an object. The lower die 23, for example, is composed of a punch, and the upper die 21, for example, is composed of a die. A refrigerant flow path can also be provided in the upper die 21 and the lower die 23. This allows the heat taken from the object during pressing to be released via the refrigerant. Two workpieces can be positioned between the upper die 21 and the lower die 23. The upper die 21 and the lower die 23 can move relative to each other. For the press 20, with two workpieces positioned between the upper die 21 and the lower die 23, the upper die 21 and the lower die 23 are brought closer together, thereby pressing and forming the two workpieces. The movement of the upper die 21 and the lower die 23 can be controlled, for example, by a controller 22. In this example, the lower die 23 and the upper die 21 of the press 20 are configured to simultaneously produce multiple pressed and formed articles. This is an example of a single press equipped with two sets of paired dies. In this example, multiple workpieces W1 and W2 are positioned between the lower die 23 and the upper die 21 of the press 20, and the multiple workpieces W1 and W2 are simultaneously pressed and formed. Alternatively, multiple presses 20 can be installed. For example, two presses equipped with one set of paired dies can also be installed.

[0095] (Manipulator)

[0096] The manipulator 44 uses a conveying device 46 to transport the workpiece between the conveyor table 16 and the press 20. The conveying device 46 performs actions such as lifting, holding, and placing the workpiece as the transport object. The manipulator 44 controls the position and orientation of the conveying device 46. The conveying device 46 can also be an end effector of the manipulator 44. The manipulator 44 moves the conveying device 46 between a lifted position above the conveyor table 16 and a pressing position between two pairs of molds (upper mold 21 and lower mold 23) of the press 20. The manipulator 44 includes: a base that is rotatable about at least one axis; and an arm that extends from the base and has at least one joint. The conveying device 46 is rotatably mounted at the end of the arm. Furthermore, the moving device that moves the conveying device 46 is not limited to the manipulator. For example, the moving device can also be a structure including a track connecting the conveyor table 16 and the press 20, and a suspension device that movably suspends the conveying device 46 vertically along the track.

[0097] (Controller)

[0098] The controller 22 controls the heating device 14, the conveyor 16, the press 20, and the actuator 44 (conveyor 46). The controller 22 may be composed of one or more computers, for example, equipped with a processor and memory. The processor executes the program recorded in the memory, thereby enabling control of the heating device 14, the conveyor 16, the press 20, and the actuator 44 (conveyor 46). The controller 22 sends control signals or control data to the heating device 14, the conveyor 16, the press 20, and the actuator 44 (conveyor 46). Additionally, the controller 22 may also receive signals or data indicating the status of the heating device 14, the conveyor 16, the press 20, and the actuator 44 (conveyor 46). As an example, the controller 22 may also include a control unit (e.g., composed of circuitry or a processor) located at the heating device 14, the conveyor 16, the actuator 44, and the press 20 to control each device. In this case, the controller 22 may also include an overall control computer that supplies control information to the control units of each device to control the overall operation of the hot pressing production line 10. The movement of the arm 71 of the conveying device 46, described later, may also be controlled by a part of the controller 22, such as the control unit of the manipulator 44.

[0099] (Conveying device)

[0100] The conveying device 46 includes a base 48 and at least a pair of arms 71 rotatably mounted on the base 48. A connector 56 is provided on the upper surface of the base 48 and is connected to the actuator 44. The connector 56 is connected so that the base 48 can rotate relative to the actuator 44 about the vertical axis.

[0101] A pair of arms 71 are separately arranged in the transverse direction (perpendicular to the vertical direction) of the base 48. Each pair of arms 71 has a base extending from the base 48 in the vertical direction and a claw extending laterally from the base. By controlling the rotation of the arms 71 relative to the base 48, it is possible to control the arms 71 to a closed state where the claws are close to each other and an open state where the claws are far apart.

[0102] (tray)

[0103] Figure 2 This is a top view of tray 1 taken from above. Figure 3 Observing from the direction of arrow F Figure 2 The side view shown is of tray 1. Tray 1 is a heated conveying tray for hot-pressed raw materials (workpieces). Tray 1 is configured to withstand the heating temperature of the workpiece. Figure 2In the example shown, the tray body 2 has a shape extending along a surface perpendicular to the vertical direction and includes a hollow portion 2G extending vertically through it. When viewed from above, the area of ​​the hollow portion 2G is wider than the area of ​​the constituent components of the tray body 2. The tray 1 has a plurality of supports 3 extending upward from the tray body 2. The plurality of supports 3 includes a first support group 3a capable of placing a first workpiece W1 and a second support group 3b capable of placing a second workpiece W2 above the first workpiece W1. Both the first support group 3a and the second support group 3b are located between the hollow portions 2G of the tray body 2 when viewed from above.

[0104] (Pallet body)

[0105] exist Figure 2 In the example shown, the pallet body 2 has a frame 2c and rod members 2f mounted inside the frame 2c. The frame 2c includes a pair of longitudinal frames 2b and a pair of transverse frames 2a. The pair of longitudinal frames 2b are separated laterally and arranged parallel to each other. The pair of transverse frames 2a are separated longitudinally and arranged parallel to each other between the pair of longitudinal frames 2b. The pair of longitudinal frames 2b and the pair of transverse frames 2a form a rectangular frame 2c when viewed from above. The rod members 2f include longitudinal rod members 2d and transverse rod members 2e. The longitudinal rod members 2d are mounted between the pair of transverse frames 2a. The transverse rod members 2e are mounted between the pair of longitudinal frames 2b. In the frame 2c, the rod members 2f are arranged in a grid pattern.

[0106] It can also be configured to allow adjustment of the position of the rod member 2f (at least one of the longitudinal rod member 2d and the transverse rod member 2e) within the frame 2c. For example, multiple positioning holes or locking pieces can be provided in the frame 2c. In this case, the rod member 2f is fixed to the holes or locking pieces in the frame 2c using fasteners or the like as needed. By changing the position of the holes or locking pieces for fixing the rod member 2f, the position of the rod member 2f within the frame 2c can be adjusted.

[0107] Furthermore, the structure of the pallet body 2 is not limited to Figure 2 The example shown. For instance, the pallet body can also be formed in a ladder shape, having: a pair of longitudinal members that are separated and arranged substantially parallel to each other; and a plurality of transverse members that are positioned between the pair of longitudinal members in a direction intersecting the pair of longitudinal members. Alternatively, the pallet body can also be formed from a plate-like member having a plurality of through holes running vertically as a hollow portion.

[0108] The constituent components of the pallet body 2 (in) Figure 2In the example, frame 2c and rod member 2f can be either tubular or solid material. Furthermore, the constituent components of the pallet body 2 can be either angle members with an L-shaped cross-section or channel members with a U-shaped cross-section. The material of the constituent components of the pallet body 2 is not particularly limited and can be formed from heat-resistant materials such as heat-resistant steel or ceramics. Preferably, the maximum operating temperature of the constituent components is set to, for example, a range of 900°C or higher, commonly used in heating devices, and 1050°C or lower, which is the upper limit set temperature of the heating device. Examples of heat-resistant steels (heat-resistant alloy steels) that can be used as constituent components include SCH22 (0.4C-25Cr-20Ni) and SCH24 (0.4C-25Cr-35Ni-Mo, Si). Using heat-resistant alloy steel to form the constituent components of the pallet body 2 simplifies processing and manufacturing.

[0109] (pillar)

[0110] The first support group 3a includes at least three supports forming a triangle when viewed from above, with virtual straight lines connecting the supports to each other. The second support group 3b includes at least three supports forming a triangle when viewed from above, with virtual straight lines connecting the supports to each other. When viewed from above, each of the second support groups 3b is positioned differently from the first support group 3a. Each of the second support groups 3b is higher than the lowest support in the first support group 3a. Therefore, the first support group 3a can support the first workpiece W1. In addition, the second support group 3b can support the second workpiece W2 above the first workpiece W1 supported by the first support group 3a.

[0111] Viewed from above, the second support group 3b is positioned in the area where the second workpiece W2 is placed, and in an area that does not overlap with the area where the first workpiece W1 is placed. Furthermore, viewed from above, the second support group 3b is configured not to overlap with the area where the first workpiece W1 is placed. That is, the second support group 3b is configured so that when the first workpiece W1 is lifted upwards by the conveyor 46, the first workpiece W1 will not snag on the second support group 3b.

[0112] There is no particular limitation on the number of supports in the first support group 3a and the second support group 3b. The number of supports in the first support group 3a and the second support group 3b can be the same or different. For example, if it is desirable to strengthen the support of the second workpiece W2 compared to the first workpiece W1, considering the characteristics and support positions of the first workpiece W1 and the second workpiece W2, the number of supports in the second support group 3b can be more than the number of supports in the first support group 3a.

[0113] The first support group 3a and the second support group 3b (hereinafter referred to as support 3 unless otherwise specified) are formed, for example, in the shape of a cylinder or prism, or in the shape of a cone or pyramid. Support 3 can be solid or tubular. The material of support 3 is not particularly limited, but it is formed of heat-resistant materials such as heat-resistant steel or ceramics. Preferably, the maximum operating temperature of support 3 is set to, for example, 900°C or higher, which is commonly used in heating devices, and 1050°C or lower, which is the upper limit set temperature of the heating device. Examples of heat-resistant steels (heat-resistant alloy steels) that can be used as constituent components of support 3 include SCH22 (0.4C-25Cr-20Ni) and SCH24 (0.4C-25Cr-35Ni-Mo, Si). Support 3 is fixed to tray body 2. For example, support 3 can also be installed on tray body 2 in a state where it is inserted into a hole provided by tray body 2. In this case, for example, the support column 3 can be fixed to the pallet body 2 by engaging the external thread on the outer periphery of the end of the support column 3 with the internal thread on the inner periphery of the hole in the pallet body 2. Alternatively, the support column 3 can be pressed into the hole in the pallet body 2. Furthermore, the fixing mechanism for the support column 3 is not limited to the hole in the pallet body 2. Other fixing mechanisms can also be used to fix the support column 3 to the pallet body 2.

[0114] (Example of the configuration of workpiece 1 and workpiece 2)

[0115] exist Figure 2 In the example shown, when viewed from above, the first workpiece W1 has a notch at its edge (end). A second support group 3b is disposed in the area corresponding to the notch of the first workpiece W1. Thus, by distributing the second support group 3b in the area corresponding to the notch or hole of the first workpiece W1, it is possible to distribute the second support group 3b in an area that does not overlap with the first workpiece W1 when viewed from above. For example, at least one support of the second support group 3b can be disposed in the area corresponding to a positioning hole of the first workpiece W1. The positioning hole is a hole used for positioning the first workpiece W1 during press forming.

[0116] Figure 4 This is a top view showing another example of the configuration of the first support group 3a and the second support group 3b. Figure 5 Observing from the direction of arrow F Figure 4 The side view obtained from tray 1 shown. Figure 4 and Figure 5In the example shown, the first workpiece W1 and the second workpiece W2, which are of the same shape, are positioned offset when viewed from above. That is, the first workpiece W1 and the second workpiece W2 are positioned such that a portion of the second workpiece W2 does not overlap with the first workpiece W1 when viewed from above. The second support group 3b is positioned in the area where the second workpiece W2 is located, and in a position that does not overlap with the area where the first workpiece W1 is located. In this case, it is also possible that no notches, holes, etc. are provided in the first workpiece W1. Figure 4 In the example shown, when viewed from above, the shape of the first workpiece W1 is formed by rotating the second workpiece W2 by 180 degrees with the normal direction of the plate surface as the axis.

[0117] exist Figures 2-5 In the example shown, the difference in height (length in the vertical direction) between the second support group 3b and the first support group 3a is ΔH. This allows for the provision of at least three pairs of first support groups 3a and second support groups 3b that are ΔH higher than them. Consequently, they can be arranged in a vertically overlapping configuration with the lower surfaces of the first workpiece W1 and the second workpiece W2 separated by ΔH. For example, as... Figures 2-5 As in the example, when both the first workpiece W1 and the second workpiece W2 are flat plates, the height of all supports in the first support group 3a is the same, and the height of all supports in the second support group 3b is the same. Therefore, the second support group 3b is always ΔH higher than the first support group 3a. When ΔH is equal to the thickness of the first workpiece W1, the upper surface of the first workpiece W1 and the lower surface of the second workpiece W2 are in contact.

[0118] The first workpiece W1 and the second workpiece W2 may not be flat plates. Figure 6 and Figure 7 This is a side view showing an example of a support group where the first workpiece W1 and the second workpiece W2 are not flat plates. Figure 6 This example illustrates the case where the first workpiece W1 and the second workpiece W2 are intermediate formed products of the same shape. In this example, both the first workpiece W1 and the second workpiece W2 are machined into a cap shape with the same cross-sectional shape. In this example, at least three pairs of first support pillars 3a and second support pillars 3b that are ΔH higher than them are also provided. The distance between the lower surfaces of the first workpiece W1 and the lower surfaces of the second workpiece W2 in the vertical direction is ΔH.

[0119] like Figure 7 As shown, the cross-sectional shapes of the first workpiece W1 and the second workpiece W2 can also be different. In this example, at least three pairs of first support pillars 3a and second support pillars 3b that are ΔH higher than them are also provided.

[0120] The distance between the first workpiece W1 and the second workpiece W2 carried on the pallet 1 depends on the height difference ΔH between the first support group 3a and the corresponding second support group 3b. That is, ΔH determines the vertical distance D between the first workpiece W1 and the second workpiece W2 on the pallet 1 during heating and conveying. Preferably, the maximum value of the distance D between the first workpiece W1 and the second workpiece W2 on the pallet 1 during heating and conveying is, for example, 100 mm or less. From the viewpoint that the first workpiece W1 and the second workpiece W2 carried on the pallet 1 are subject to radiant heat from each other and the temperature drop is suppressed, it is preferable to have a smaller distance D. The maximum value of the distance D is more preferably 50 mm or less, further preferably 30 mm or less, and even more preferably 10 mm or less. The lower limit of the distance D is not particularly limited, however, the distance required for the loading and lifting action on the pallet 1 is the lower limit of the distance D. The preferred range of ΔH is the same as the value obtained by adding the maximum plate thickness of the first workpiece W1 to the preferred range of the distance D. For example, when the first workpiece W1 is a workpiece with a plate thickness of about 3 mm, the preferred range of ΔH can be 3 mm to 103 mm.

[0121] Figure 8 This is a top view of an example of tray 1 where the areas of the first workpiece W1 and the second workpiece W2, as viewed from above, are different. Figure 9 Observing from the direction of arrow F Figure 8 The side view obtained from tray 1 shown. Figure 8 and Figure 9 In the example shown, the area of ​​the second workpiece W2 is larger than the area of ​​the first workpiece W1. It is also possible to make the dimensions of the first workpiece W1 and the second workpiece W2 different. The second workpiece W2 overlaps the entire first workpiece W1 in the vertical direction. Therefore, when viewed from above, the end (edge) of the second workpiece W2 is located outside the end (edge) of the first workpiece W1. When viewed from above, the second support group 3b is disposed in the region between the end of the second workpiece W2 and the end of the first workpiece W1. That is, when viewed from above, the second support group 3b is disposed in the region of the second workpiece W2 that does not overlap with the first workpiece W1. Therefore, even if the first workpiece W1 does not have notches, holes, etc., the first support group 3a and the second support group 3b can be used to support the first workpiece W1 and the second workpiece W2 in an overlapping state. In this case, when viewed from above, the second support group 3b is disposed in the region outside the region where the first support group 3a is disposed.

[0122] The distance ΔW between the end of the second workpiece W2 placed in the second support group 3b when viewed from above and the end of the first workpiece W1 placed in the first support group 3a when viewed from above is not particularly limited; however, it is preferable that this distance ΔW is 30 mm or less. If ΔW is too long, the area at the end of the second workpiece W2 that does not overlap with the first workpiece W1 becomes larger. In this case, the effect of suppressing the temperature drop at the end of the second workpiece W2 becomes less effective. From this point of view, ΔW is more preferably 20 mm or less, and even more preferably 15 mm or less. If ΔW is too short, it becomes difficult to ensure the area where the second support group 3b is positioned. From this point of view, the minimum value of ΔW is preferably 5 mm or more, more preferably 8 mm or more, and even more preferably 10 mm or more.

[0123] Furthermore, ΔW is defined as the distance from the end of the second workpiece W2 to the end of the first workpiece W1 in a direction perpendicular to the line at the end of the second workpiece W2 (or the direction of the normal if the line at the end is a curve) when viewed from above.

[0124] exist Figure 8 and Figure 9 In this configuration, both the first workpiece W1 and the second workpiece W2 are flat plates. However, at least one of the first workpiece W1 and the second workpiece W2 may not be a flat plate but an intermediate formed product. In this case, it is also possible to configure the area of ​​the second workpiece W2 placed on the second support group 3b, as viewed from above, to be larger than the area of ​​the first workpiece W1 placed on the first support group 3a.

[0125] exist Figure 9 In the example shown, the thickness of the second workpiece W2 is greater than that of the first workpiece W1. The smaller the thickness, the faster the temperature drops. Therefore, by arranging the thinner first workpiece W1 and the thicker second workpiece W2 in an overlapping configuration, the temperature drop suppression effect of the first workpiece W1 can be improved. As a result, the temperature drop suppression effect can be improved as a whole for both the first and second workpieces W1. Furthermore, the thicknesses of the first and second workpieces W1 can also be the same.

[0126] (Example of a plate with varying thickness)

[0127] At least one of the first workpiece W1 and the second workpiece W2 may also be a differential thickness plate including a thick-walled portion and a thin-walled portion. Figure 10 This is a side view illustrating an example where workpiece W1 and workpiece W2 are plates of different thicknesses. Figure 10In the example shown, the thick-walled portion of the first workpiece W1, placed in the first support group 3a, and the thin-walled portion of the second workpiece W2, placed in the second support group 3b, overlap vertically. This allows for transport in a configuration where the thin-walled portion, which is thinner and more easily cooled in one workpiece, is opposite to the thick-walled portion, which has a larger heat capacity in the other workpiece. Therefore, temperature drop in the thin-walled portions of both workpieces can be more effectively suppressed. Consequently, overall temperature drop in both workpieces can be effectively suppressed, and temperature differences between the thin-walled and thick-walled portions of each workpiece can be effectively suppressed.

[0128] For example, if the first workpiece W1 and the second workpiece W2 have the same shape and the same distribution of thin-walled and thick-walled portions, after the first workpiece W1 is supported on the first support group 3a, the second workpiece W2 can be supported on the second support group 3b with its orientation rotated (e.g., 180 degrees) about the vertical axis to a different orientation than that of the first workpiece W1. At this time, the orientation, i.e., the amount of rotation, of the second workpiece W2 can be adjusted such that at least a portion of the thick-walled portion of the first workpiece W1 and at least a portion of the thin-walled portion of the second workpiece W2 overlap when viewed from above.

[0129] Furthermore, differential thickness plates can also be welded plates obtained by butt-joining the ends of steel plates with different thicknesses. Alternatively, differential thickness plates can also be patch welded plates obtained by overlapping and joining steel plates of different sizes. Alternatively, differential thickness plates can also be differential thickness rolled plates obtained by locally changing the thickness of a single steel plate through processes such as rolling.

[0130] (Shielding panel)

[0131] Figure 11 This is a top view showing a structural example of a tray 1 equipped with shielding plates 4 (4A to 4D). Figure 12 Observing from the direction of arrow F Figure 11 The side view obtained from the tray 1 shown. Figure 11 and Figure 12 The tray 1 shown is a pair Figure 1 and Figure 2 The tray 1 shown is a structure obtained by adding shielding plates 4 (4A-4D). Figure 11 As shown, when viewed from above, shielding plates 4A to 4D are provided to surround the entire circumference of the pallet body 2. The shielding plates 4 include a pair of shielding plates 4A and 4C that cover the short side (short side) of the pallet body 2 when viewed from above, and a pair of shielding plates 4B and 4D that cover the long side (long side) of the pallet body 2.

[0132] like Figure 12As shown, shielding plates 4A to 4D cover the height region between the lowest and highest pillars of the first pillar group 3a and the second pillar group 3b from the side (perpendicular to the vertical direction). That is, shielding plates 4A to 4D are formed extending from a position lower than the lowest pillar to a position higher than the highest pillar. Therefore, shielding plates 4A to 4D can be used to prevent air from flowing into the space between the first workpiece W1 carried in the first pillar group 3a and the second workpiece W2 carried in the second pillar group 3b.

[0133] The shielding panels 4A to 4D are installed on the pallet body 2. Figure 12 In the example shown, shielding panels 4B and 4D are attached to the side surface of the pallet body 2 and are formed extending upwards. The shielding panel 4 is attached to the pallet body 2, for example, by fastening members such as welding or bolts. Alternatively, the shielding panel 4 can be attached to and detached from the pallet body 2.

[0134] exist Figure 11 and Figure 12 In the example shown, the shielding plates 4A to 4D each have an inclined surface that slopes towards the support 3, i.e., the first workpiece W1 and the second workpiece W2, as it approaches the ends from the center. In other words, the shielding plates 4A to 4D are each curved, with the central portion protruding outwards and the ends located further inwards than the central portion. This allows air encountering the shielding plates 4 to be guided away from the first workpiece W1 and the second workpiece W2 carried on the tray 1. Figure 12 As shown, for shielding plates 4B and 4D, whether viewed from above or from the side, the central part is located on the outer side of the end.

[0135] Furthermore, the shape of the shielding plate 4 is not limited to the example described above. For example, the shielding plate 4 may also be formed of a flat plate. It may also be shaped such that, in either the side view or the top view, the central portion is located further outward than the ends.

[0136] The location of the shielding plate 4 is not limited to... Figure 11 and Figure 12 The example shown. In Figure 11 In the example shown, shielding plates 4B and 4D covering the long side and shielding plates 4A and 4C covering the short side are provided. Alternatively, the structure could utilize shielding plates 4 to cover at least one of the long and short sides. By using shielding plates 4 to cover the long side, air inflow can be blocked over a larger area. Furthermore, the structure could utilize shielding plates 4 to cover at least the front side in the conveying direction. This allows for more efficient blocking of air inflow during conveying.

[0137] [Example of manufacturing process for pressed molded products]

[0138] Refer again Figure 1 An example of a process for manufacturing a pressed molded article using the hot pressing production line 10 described above will be explained. The manufacturing process of the pressed molded article in this embodiment includes: a heating process for heating the first workpiece W1 and the second workpiece W2, a conveying process for conveying the first workpiece W1 and the second workpiece W2, and a pressing process for pressing the first workpiece W1 and the second workpiece W2.

[0139] (Heating process)

[0140] In the heating process, the first workpiece W1 and the second workpiece W2 are heated within the heating device 14 while being supported on the tray 1. For example, as Figures 2 to 12 As shown, the first workpiece W1 is supported by the first support group 3a, and the second workpiece W2 is supported by the second support group 3b. The first workpiece W1 and the second workpiece W2, which are supported on the pallet 1, overlap in the vertical direction, that is, in the direction normal to the surface of the first workpiece W1.

[0141] The tray body 2 has a hollow portion 2G that runs vertically through the tray. Therefore, even if there is a heat source below the tray 1, the heat transfer from the heat source to the first workpiece W1 and the second workpiece W2 is not easily hindered by the tray body 2.

[0142] A tray 1 carrying workpieces W1 and W2 enters the heating chamber of the heating device 14 through inlet 14B. The tray 1 is conveyed to outlet 14A by indoor rollers 13. The heating device 14 heats workpieces W1 and W2 to a predetermined heating temperature while conveying them. This heating temperature is, for example, set above the Ac3 phase transformation point, the temperature at which the ferrite of the steel constituting workpieces W1 and W2 completes its austenite transformation.

[0143] Alternatively, a conveying device and manipulator can be provided to sequentially overlap the first workpiece W1 and the second workpiece W2 on the tray 1 before it enters the heating device 14. This conveying device places the first workpiece W1 on the first support group 3a of the tray 1, and then places the second workpiece W2 on the second support group 3b. This conveying device can, for example, employ a... Figure 1 The conveying device 46 shown is identical in structure to the one that lifts the first workpiece W1 and the second workpiece W2 and places them in the pressing position. This conveying device is located upstream of the heating device 14.

[0144] (First conveying process)

[0145] In the first conveying process, the first workpiece W1 and the second workpiece W2, supported on the tray 1, emerge from the heating device 14 and are conveyed to the lifting position, the junction point where they are transferred to the conveying device 46. Thus, the first workpiece W1 is placed on the first support group 3a, and the second workpiece W2 is placed on the second support group 3b, overlapping the first workpiece W1. In this state, together with the tray 1, they are conveyed from the heating device 14 to the lifting position. Outside the heating device 14, the tray 1 is conveyed by the conveying rollers 26 to the vicinity of the press 20. For example, with... Figures 2 to 12 The illustrated method involves placing the first workpiece W1 and the second workpiece W2 on the tray 1 and conveying them from the heating device 14 to the lifted position. The positional relationship between the first workpiece W1 and the second workpiece W2 in the first conveying step is the same as that in the heating step. That is, the first workpiece W1 and the second workpiece W2 can be conveyed to the lifted position in the first conveying step while maintaining their positional relationship during heating using the tray 1. As a result, the temperature drop of the first workpiece W1 and the second workpiece W2 during conveying is mitigated. Furthermore, even without a heat source such as a heater that generates heat energy in the conveying path, the temperature drop of the workpieces during conveying can be mitigated. Therefore, the temperature drop can be easily mitigated.

[0146] In addition, the tray 1 can also be used for heating and conveying processes of other workpieces after the first workpiece W1 and the second workpiece W2 are lifted by the conveying device 46 and conveyed to the pressing position.

[0147] (Second conveying process)

[0148] In the second conveying process, near the press 20, the second workpiece W2, placed in the second support group 3b, is lifted upwards by the conveying device 46. Then, the first workpiece W1, placed in the first support group 3a, is lifted upwards by the conveying device 46. As described above, the conveying device 46 moves upwards while the first workpiece W1 is held by the arm 71. The first workpiece W1 moves upwards while maintaining the same posture as when placed in the first support group 3a. At this time, the second support group 3b is configured so that it does not overlap with the first workpiece W1 placed in the first support group 3a when viewed from above, and therefore will not snag on the first workpiece W1 lifted upwards by the conveying device 46. Therefore, the control or device structure for lifting the first workpiece W1 can be simplified.

[0149] Furthermore, the conveying device that lifts the second workpiece W2 and the conveying device that lifts the first workpiece W1 may not necessarily be the same device. The first workpiece W1 and the second workpiece W2, lifted by the conveying device 46, are respectively positioned in a pressing position. The pressing position is, for example, between the upper die 21 and the lower die 23 of the press 20.

[0150] Furthermore, the pressing positions of the first workpiece W1 and the second workpiece W2 can be the same or different. Alternatively, the first workpiece W1 and the second workpiece W2 can be set at different positions on the die of one press 20. Alternatively, two presses 20 can be used. In this case, the first workpiece W1 can be set on the die of one of the two presses 20, and the second workpiece W2 can be set on the die of the other press.

[0151] (Pressing process)

[0152] Press 20 uses upper die 21 and lower die 23 to press and form first workpiece W1 and second workpiece W2. Here, the first workpiece W1 and second workpiece W2, which are the objects of pressing and forming, are workpieces that have been heated above the Ac3 phase transition point by heating device 14 and then conveyed to the pressing position via conveyor table 16 and conveyor device 46. Press 20 can begin pressing and forming of the first workpiece W1 and second workpiece W2 using upper die 21 and lower die 23, and can perform quenching treatment together with the forming process. Specifically, with the first workpiece W1 and second workpiece W2 positioned between upper die 21 and lower die 23, press 20 moves upper die 21 relatively close to lower die 23 and to the lower stop point for forming. After reaching the lower stop point, in the mold-closed state, upper die 21 and lower die 23 contact the first workpiece W1 and second workpiece W2, rapidly absorbing heat from them. This causes the first workpiece W1 and the second workpiece W2 to undergo martensitic or bainitic phase transformation. As a result, the first workpiece W1 and the second workpiece W2 can be made into shaped products that correspond to the upper mold 21 and the lower mold 23 and are formed by quenching.

[0153] The present invention is not limited to the embodiments described above. For example, in the above embodiments, an example of two workpieces (the first workpiece W1 and the second workpiece W2) being carried on the pallet 1 in an overlapping manner in the vertical direction was described, but it is also possible to carry three or more workpieces on the pallet 1 in an overlapping manner in the vertical direction.

[0154] [Workpiece Material]

[0155] The workpiece can be made of any formable metal. However, the material is not limited to this; examples include Fe-based carbon steel, stainless steel, Al-based materials, and Ti-based materials. Additionally, the workpiece may have a coating. For example, the workpiece may be a coated steel sheet. Examples of coatings include aluminum alloys, aluminum alloys, zinc alloys, or zinc alloys.

[0156] When the workpiece is a coated steel sheet, it is preferable to minimize the formation of oxide scale during transport. If oxide scale forms on the lower surface of the upper second workpiece W2 during the transport of two workpieces W1 and W2 stacked on pallet 1, the oxide scale may detach and fall onto the upper surface of the lower first workpiece W1. Additionally, oxide scale formed on the lower surface of the lower first workpiece W1 may also detach. In such cases, there is a possibility that the difference in the amount of oxide scale adhering to the upper and lower surfaces of the lower first workpiece W1 becomes greater than the difference in the amount of oxide scale adhering to the upper and lower surfaces of the upper second workpiece W2. This difference in oxide scale adhering can lead to differences in the frictional characteristics of the die and the workpiece surfaces during pressing. As a result, it may be necessary to individually adjust the die and set the forming conditions for each workpiece. Therefore, by using coated steel sheets for the workpiece, the formation of oxide scale during transport can be suppressed, and deviations in workpiece characteristics can be prevented.

[0157] [The effect of transporting multiple workpieces at intervals]

[0158] In the example above, the first workpiece W1 and the second workpiece W2 are conveyed in a state of overlapping at intervals along the vertical direction on the pallet 1. As a result, deviations in the characteristics of the upper and lower surfaces of each workpiece, as well as deviations in the characteristics of the upper and lower surfaces between the upper and lower workpieces, can be suppressed.

[0159] When workpieces W1 and W2 are transported overlapping without gap, the contact time between the overlapping surface and the opposite surface of each workpiece with air differs. In this case, if workpieces W1 and W2 are uncoated steel sheets, the amount of oxide scale formed on the upper and lower surfaces will also differ. If the amount of oxide scale differs between the upper and lower surfaces, differences in the frictional characteristics of the upper and lower surfaces may occur. Furthermore, if the orientation of the overlapping surface and the opposite surface of workpieces W1 and W2 is reversed, differences in frictional characteristics may also occur between workpieces W1 and W2. As a result, the time required for die adjustment and forming condition setting during pressing may increase. Additionally, when coated steel workpieces W1 and W2 are heated overlapping without gap during the heating process, the heating rates on the overlapping and opposite surfaces of the workpieces differ, potentially resulting in differences in the temperature history. In this case, the alloying of the coating and the base material creates differences on the upper and lower surfaces of the workpiece, sometimes resulting in differences in coating quality. Therefore, by heating and conveying the first workpiece W1 and the second workpiece W2 separately, deviations in characteristics such as frictional properties and coating quality on the upper and lower surfaces of the workpieces can be reduced.

[0160] [A variation of the hot pressing production line]

[0161] Figure 13 This is a diagram showing a modified example of the hot pressing production line 10. Figure 13 The hot pressing production line 10 shown includes a heating device 14, a conveyor table 16, a manipulator 44, a conveying device 46, a press 20, and a controller 22. Figure 13 In the hot pressing production line 10, apart from the conveying device 46, it can be connected with... Figure 1 It is constructed in the same way.

[0162] (Conveying device)

[0163] Figure 14A It means Figure 13 A side view of the structure of the conveying device 46 as seen from the transverse (y direction). Figure 14B It means Figure 14A The diagram shows the first arm 71 of the conveyor 46 in the state of being opened outwards.

[0164] (Framework)

[0165] exist Figure 14A and Figure 14B In the example shown, the conveying device 46 includes a base 48 and a pair of first arms 71 and a pair of second arms 72 rotatably mounted on the base 48. When viewed from above, the base 48 is rectangular in shape. In this example, the vertical direction is defined as the z-direction. The direction in the plane perpendicular to the vertical direction is defined as the horizontal direction. In the horizontal direction, the direction of the long side of the base 48 is defined as the y-direction, and the direction of the short side of the base 48 is defined as the x-direction.

[0166] A connector 56 is provided on the upper surface of the base frame 48 and is connected to the actuator 44. The connector 56 is connected so that the base frame 48 can rotate relative to the actuator 44 about the vertical axis.

[0167] (Arm 1 and Arm 2)

[0168] A pair of first arms 71 are separately arranged laterally (x-direction). Each pair of first arms 71 has a first base 71a extending vertically from the base 48 and a first claw 71b extending laterally from the first base 71a. Each first arm 71 is rotatably mounted on the base 48 about a rotation axis 60 in the y-direction. One end of the first base 71a is rotatably connected to the base 48 relative to the base 48, and the first claw 71b extends from the other end of the first base 71a.

[0169] A pair of second arms 72 are separately arranged laterally (x-direction). Each pair of second arms 72 has a second base 72a extending vertically from the base 48, and a second claw 72b extending laterally from the second base 72a. Each second arm 72 is rotatably mounted on the base 48 about a rotation axis 60 in the y-direction. One end of the second base 72a is rotatably connected to the base 48 relative to the base 48, and the second claw 72b extends from the other end of the second base 72a.

[0170] The vertical positions of the first claw 71b and the second claw 72b are different from each other. Figure 14A and Figure 14B In the example shown, the first base 71a is longer than the second base 72a in the vertical direction. The first claw 71b is located further away from the base 48 than the second claw 72b.

[0171] exist Figure 14A and Figure 14B In the example shown, the rotation axis 60 of the first arm 71 and the rotation axis 60 of the second arm 72 are coaxial. This allows the first arm 71 and the second arm 72 to be efficiently configured on the base 48. Alternatively, the rotation axis 60 of the first arm 71 and the rotation axis 60 of the second arm 72 can also be non-coaxial.

[0172] (Drive Department)

[0173] A pair of first arms 71 are driven by a first drive unit. The first drive unit rotates the pair of first arms 71 relative to the base frame 48, thereby changing the lateral (x-direction) distance of the pair of first claws 71b. Figure 14A and Figure 14B In the example shown, the first drive unit is composed of actuators 82 disposed relative to each of the first arms 71.

[0174] The actuator 82 is, for example, a cylinder. The actuator 82 adjusts the extension of the axially moving working shaft 82A. A pin 82B is provided at the end of the working shaft 82A. The pin 82B is freely movable and rotatable into the elongated hole of the connecting rod 90 fixed in the first arm 71.

[0175] like Figure 14A As shown, when each actuator 82 extends the working shaft 82A, the corresponding first arm 71 extends downward, and the pair of first claws 71b of the pair of first arms 71 become closed by bringing them close together. Additionally, as... Figure 14B As shown, when each actuator 82 retracts the working shaft 82A, the pair of first claws 71b of the pair of first arms 71 move away from each other and become open.

[0176] A pair of second arms 72 are driven by a second drive unit (not shown). The second drive unit rotates the pair of second arms 72 relative to the base 48, thereby changing the lateral (x-direction) distance of the pair of second claws 72b. The second drive unit driving the second arms 72 can also be configured, for example, to have... Figure 14A and Figure 14B The actuator 82 shown has the same actuator structure. The pair of second arms 72 are also controlled by the second drive unit to either be in a closed state where the pair of second claws 72b are close to each other, or in an open state where the pair of second claws 72b are far apart from each other from the closed state. Furthermore, the actuators of the first and second drive units are not limited to cylinders; for example, they could be electric motors or hydraulic cylinders.

[0177] A pair of first jaws 71b can support the lower surfaces of the two lateral ends of the first workpiece W1 in a closed state, where they are close to each other in the lateral direction. A pair of second jaws 72b can support the lower surfaces of the two lateral ends of the second workpiece W2 in a closed state, where they are close to each other in the lateral direction.

[0178] [Example of manufacturing process for pressed molded products]

[0179] For use Figure 13 An example of a process for manufacturing pressed products using the hot pressing production line 10 shown will be explained. The pressing product manufacturing process includes a heating process, a first conveying process, a second conveying process, and a pressing process. The heating process, the first conveying process, and the pressing process can be combined... Figure 1 The manufacturing process of the hot pressing production line 10 shown is carried out in the same way.

[0180] (Heating process)

[0181] In the heating process, the first workpiece W1 and the second workpiece W2 are heated in the heating device 14 while supported on the tray body 2. The first workpiece W1 and the second workpiece W2 are heated in a state where they overlap in the normal direction of the surface of the first workpiece W1. The first workpiece W1 is placed on the first support group 3a. The second workpiece W2 is placed on the second support group 3b.

[0182] (First conveying process)

[0183] In the first conveying process, the first workpiece W1 and the second workpiece W2 are conveyed from the heating device 14 to the conveying device 46 in a lifted position by the conveying table 16 while being supported on the pallet body 2.

[0184] (Second conveying process)

[0185] The second conveying process includes: a process in which the conveying device 46 simultaneously lifts the first workpiece W1 and the second workpiece W2, a process in which the first workpiece W1 and the second workpiece W2 are conveyed, a process in which the first workpiece W1 is lowered to the pressing position, and a process in which the second workpiece W2 is lowered to the pressing position.

[0186] The conveying device 46 approaches the first workpiece W1 and the second workpiece W2, which are supported on the tray 1, from above via the operation of the manipulator 44. At this time, the pair of first arms 71 and the pair of second arms 72 in the conveying device 46 are in the open state. The conveying device 46 approaches the second workpiece W2 from above with the second workpiece W2, which is placed on the second support group 3b, between the pair of second arms 72 when viewed from above. When the conveying device 46 approaches to a height that causes the second claws 72b of the second arms 72 to penetrate below the second workpiece W2 placed on the second support group 3b, the pair of second arms 72 are rotated to a closed state. As a result, the second claws 72b of the pair of second arms 72 penetrate below the lower surfaces of both ends of the second workpiece W2. The conveying device 46 is in a state where the lower surface of the second workpiece W2 is supported by the second claws 72b of the second arms 72. Figure 13 and Figure 14B The state of the conveyor 46 supporting the second workpiece W2 with the second arm 72 is shown.

[0187] With the second workpiece W2 supported by the second arm 72, the conveying device 46 rotates the first arm 71 to a closed state. This causes the first claws 71b of the pair of first arms 71 to drill under the lower surfaces of both ends of the first workpiece W1. The conveying device 46 is now in a state where the lower surface of the first workpiece W1 is supported by the first claws 71b of the first arms 71. In this state, the conveying device 46 moves upward by the action of the manipulator 44. This simultaneously lifts the first workpiece W1 and the second workpiece W2. Furthermore, in this example, the actions of rotating the second arm 72 to support the second workpiece W2 and rotating the first arm 71 to support the first workpiece W1 are performed sequentially; however, these two actions can also be simultaneous or reversed in sequence.

[0188] The conveying device 46 conveys a first workpiece W1 whose lower surface is supported by a pair of claws of the first arm 71 and a second workpiece W2 whose lower surface is supported by a pair of claws of the second arm 72, in a state in which they overlap each other in the normal direction of the plate surface of the first workpiece W1.

[0189] Figure 13The diagram shows the state immediately after the conveyor 46 has placed the first workpiece W1 into the pressing position. When placing the first workpiece W1, the conveyor 46, with the first workpiece W1 supported by the claws (first claws 71b) of a pair of first arms 71, places the first workpiece W1 into the pressing position, where the first arms 71 are rotated to an open position. While placing the first workpiece W1, the conveyor 46 maintains the state where the second workpiece W2 is held by the second arms 72. Then, the conveyor 46 moves to the pressing position of the second workpiece W2, drives the pair of second arms 72 to an open position, and places the second workpiece W2 into the pressing position.

[0190] exist Figure 13 The example shown illustrates two workpieces positioned on the upper die 21 and lower die 23 of a single press, with both workpieces being pressed simultaneously. In this case, the first workpiece W1 and the second workpiece W2 are lowered to different pressing positions between the upper die 21 and the lower die 23, respectively. The manner in which the conveying device 46 lowers the two held workpieces to their respective pressing positions is not limited to this. For example, it could also be that the first workpiece W1 and the second workpiece W2 are lowered to their respective pressing positions on two separate presses.

[0191] (Experimental Example)

[0192] The steel plates were heated, and the temperature change after heating was measured under varying conditions. Specifically, the following experiments were conducted. 1.5 GPa grade hot-pressing steel plates with thicknesses of 0.8 mm and 1.6 mm were used as test materials, and thermocouples were installed on the surface of the steel plates to measure the temperature. The steel plates were heated to 950°C using a heating furnace, and the temperature drop during air cooling after removal from the furnace was measured. Comparative Example 1 used the condition of heating and naturally cooling a single 1.6 mm thick steel plate, Comparative Example 2 used the condition of heating and naturally cooling a single 0.8 mm thick steel plate, and Example 3 used the condition of overlapping two 0.8 mm thick steel plates in the normal direction of the plate surface and arranging them at a predetermined interval D and fixing them. Under the condition of overlapping two steel plates, the interval D was set to three standards: 10 mm, 30 mm, and 50 mm, which were respectively set as Example 1, Example 2, and Example 3. Figure 15 This indicates the temperature measurement locations. The temperatures of the upper and lower steel plates were measured at distances of 5mm, 20mm, 30mm, and 50mm from the ends of the steel plates, as well as at the center of the steel plates.

[0193] Figure 16 This is a graph representing the average cooling rate as a result of the measurements. The average cooling rate was derived from the measured temperature drop curve, from 800℃ to 750℃. Figure 17 This is a graph representing the range of the object derived as the average cooling rate. From Figure 16 The results confirmed that, at all measurement locations, compared to the condition of a single 0.8mm thick steel plate (Comparative Example 1), the average cooling rate of two 0.8mm thick steel plates stacked vertically (Examples 1-3) could be reduced. It was also confirmed that, when two steel plates are stacked, a smaller interval D between the two plates reduces the average cooling rate near the ends of the plates, and the improvement in average cooling rate is significant at all measurement locations. In Example 3, where the interval D was set to 50mm, the cooling rate was improved to an intermediate level between the conditions of a single 0.8mm thick steel plate (Comparative Example 1) and a single 1.6mm thick steel plate (Comparative Example 2). In Example 1, where the interval D was set to 10mm, the cooling rate was improved to the same extent as in Comparative Example 2, where a single 1.6mm thick steel plate was used. By appropriately setting the interval D between two overlapping steel plates, it is possible to obtain the same cooling characteristics as a steel plate with twice the thickness, i.e. twice the heat capacity.

[0194] As can be seen from the above results, when multiple workpieces are conveyed overlapping in the vertical direction, it is important to maintain an appropriate distance between the workpieces from the viewpoint of reducing the cooling rate. In the above embodiment, the interval between the first and second workpieces carried on the tray can be stably maintained during the heating process and the subsequent conveying process. Therefore, the temperature drop of the first and second workpieces can be suppressed, and the conveying can be performed simply and efficiently.

[0195] Explanation of reference numerals in the attached figures

[0196] 1. Pallet; 2. Pallet body; 3. Support; 3a. First support group; 3b. Second support group; W1. First workpiece; W2. Second workpiece.

Claims

1. A method of manufacturing a press-formed product, wherein the method of manufacturing a press-formed product has: a heating step of simultaneously heating a first workpiece in a plate shape and a second workpiece in a plate shape; a conveying step of conveying the first workpiece and the second workpiece heated in the heating step to a press; and a pressing step of processing the first workpiece and the second workpiece conveyed to the press by the press, in the heating step, the first workpiece is placed on a first pillar group of at least three pillars that extend upward from a tray main body having a hollow portion that penetrates upward and downward when viewed from above, the second workpiece is placed on a second pillar group of at least three pillars that extend upward from the tray main body, and the second workpiece is arranged so as to overlap the first workpiece in a normal direction of a plate surface of the first workpiece above the first workpiece, and heating is performed by a heating device in the above state, the conveying step includes: a first conveying step in which the first workpiece is placed on the first pillar group, the second workpiece is placed on the second pillar group, and the second workpiece is arranged so as to overlap the first workpiece in a normal direction of a plate surface of the first workpiece above the first workpiece in the above state, and the tray main body is conveyed together with the first workpiece and the second workpiece from the heating device to a lifted position; and a second conveying step in which the second workpiece placed on the second pillar group is lifted upward by a conveying device at the lifted position and is conveyed to a pressing position of the second workpiece, and the first workpiece placed on the first pillar group is lifted upward by the conveying device at the lifted position and is conveyed to a pressing position of the first workpiece.

2. The method of manufacturing a press-formed product according to claim 1, wherein in the heating step and the first conveying step, the first workpiece placed on the first pillar group and the second workpiece placed on the second pillar group are arranged so as to overlap in a vertical direction with a gap of 100 mm or less.

3. The method of manufacturing a press-formed product according to claim 1, wherein in the heating step and the first conveying step, a maximum gap D in a vertical direction between the first workpiece placed on the first pillar group and the second workpiece placed on the second pillar group, and a minimum plate thickness t of a thinnest portion of the first workpiece and the second workpiece are in a relationship of the following expression: D ≤ 120t, wherein the gap D and the minimum plate thickness t are in mm.

4. The method of manufacturing a press-formed product according to any one of claims 1 to 3, wherein an area of a plate surface of the second workpiece is larger than an area of a plate surface of the first workpiece, in the heating step and the first conveying step, the first workpiece placed on the first pillar group and the second workpiece placed on the second pillar group overlap in a vertical direction.

5. The method of manufacturing a press-formed product according to any one of claims 1 to 3, wherein ​ The second workpiece has a larger plate thickness than the first workpiece.

6. The method of producing a press-formed product according to claim 4, wherein In the heating step and the first conveying step, a minimum value of a distance ΔW between an end portion of the second workpiece placed in the second pillar group, as viewed from above, and an end portion of the first workpiece placed in the first pillar group, as viewed from above, is 5 mm or more.

7. The method of producing a press-formed product according to claim 4, wherein In the heating step and the first conveying step, a maximum value of a distance ΔW between an end portion of the second workpiece placed in the second pillar group, as viewed from above, and an end portion of the first workpiece placed in the first pillar group, as viewed from above, is 30 mm or less.

8. The method of producing a press-formed product according to any one of claims 1 to 3, wherein In the first conveying step, the first workpiece placed in the first pillar group and the second workpiece placed in the second pillar group are conveyed in a state where the front in the conveying direction is covered with a shielding plate.

9. The method of producing a press-formed product according to claim 8, wherein The shielding plate has an inclined surface inclined in a manner that approaches the first workpiece and the second workpiece as it approaches from the center portion toward the end portion.

10. The method of producing a press-formed product according to claim 8, wherein At least one of the first workpiece placed in the first pillar group and the second workpiece placed in the second pillar group has a long side direction and a short side direction, The shielding plate covers the long side direction of the first workpiece placed in the first pillar group and the long side direction of the second workpiece placed in the second pillar group in the first conveying step.

11. The method of producing a press-formed product according to any one of claims 1 to 3, wherein The first workpiece and the second workpiece are differential thickness plates including thick wall portions and thin wall portions, In the heating step and the first conveying step, the thick wall portion of the first workpiece placed in the first pillar group and the thin wall portion of the second workpiece placed in the second pillar group overlap in the up-down direction.

12. A tray, wherein, The tray is used for heating and conveying of a workpiece in the shape of a plate for hot press forming, The tray includes: a tray main body having a shape extending along a surface perpendicular to the up-down direction, including a hollow portion passing through in the up-down direction; and a pillar group extending upward from the tray main body, The pillar group includes: a first pillar group of at least three pillars configured to support a lower surface of a first workpiece in the shape of a plate; and a second pillar group of at least three pillars configured to support a lower surface of a second workpiece in the shape of a plate above the first workpiece supported by the first pillar group, The first pillar group is configured such that, as viewed from above, a virtual straight line connecting the pillars to each other forms at least one triangle, The second pillar group is arranged at a position different from the first pillar group when viewed from above, and the second pillar group is arranged such that virtual straight lines connecting the pillars to each other form at least one triangle when viewed from above, and the second pillar group is higher than the lowest pillar in the first pillar group, The first pillar group and the second pillar group are used to arrange the second workpiece in a direction perpendicular to the support surface of the first workpiece so as to overlap the first workpiece, The tray main body is configured such that the area of the hollow portion is wider than the constituent members of the tray main body when viewed from above.

13. The tray according to claim 12, wherein The second pillar group includes at least three pillars that are higher than at least three pillars in the first pillar group by a certain height ΔH.

14. The tray according to claim 13, wherein The certain height ΔH is a height obtained by adding 0 mm to 100 mm to the maximum plate thickness of the first workpiece.

15. The tray according to any one of claims 12 to 14, wherein The tray further includes a shielding plate that covers a height region between the height of the lowest pillar and the height of the highest pillar in the first pillar group and the second pillar group from a direction perpendicular to the up-down direction.

16. The tray according to claim 15, wherein The shielding plate has an inclined surface that is inclined in a manner approaching the first pillar group and the second pillar group as it approaches the end portion from the central portion.

17. The tray according to claim 15, wherein The tray main body has a long side direction and a short side direction when viewed from above, The shielding plate covers the long side direction of the tray main body when viewed from above.

18. A hot press production line, wherein The hot press production line includes: the tray according to any one of claims 12 to 17; a heating device that heats the first workpiece and the second workpiece carried on the tray; a conveyance path that is arranged between the heating device and a lifted position of the first workpiece and the second workpiece, and conveys the tray from the heating device to the lifted position; a conveyance device that supports the first workpiece and the second workpiece carried on the tray at the lifted position and lifts them upward; at least one press machine having at least two pairs of dies; and a movement device that moves the conveyance device between the lifted position and a pressing position between the at least two pairs of dies.

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