Method for manufacturing press-formed product

Abstract

To efficiently alleviate a temperature drop of a heated workpiece while the heated workpiece is conveyed to a press molding position.SOLUTION: A method for manufacturing a press molding includes a heating step of simultaneously heating at least two plate-like workpieces W1 and W2 by a heating device 14, a conveyance step of conveying the two heated workpieces W1 and W2 to a press machine 20, and a press step of processing the two heated workpieces W1 and W2 by the press machine 20. The conveyance step holds the two heated workpieces W1 and W2 in a state of facing each other; in at least a part of the end of the first heated workpiece W1 out of the two heated workpieces, the end region including the end of the first heated workpiece has a shape bent toward the second heated workpiece W2; and a distance D in the opposite direction between the end of the first heated workpiece W1 and the second heated workpiece W2 is smaller than a maximum interval Dmax in the opposite direction of the two heated workpieces.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a press-formed product.

Background Art

[0002] Conventionally, a technique of pressing a material heated to a predetermined temperature with a press machine has been used. For example, in hot pressing, a hot-rolled steel sheet as a material is heated to the austenite region (about 900 °C or higher) and press-formed hot. Thereby, quenching treatment is performed together with the forming process, and a press-formed product having a strength of 1500 MPa class or higher can be obtained, for example. In general hot pressing, quenching is performed by rapid cooling due to contact heat transfer with a mold during press forming. Therefore, in order to obtain a sufficient quenching effect, it is necessary to secure the temperature of the material at the start of press forming, which roughly corresponds to the quenching start temperature, at a predetermined temperature or higher. In this case, the predetermined temperature at the start of press forming is, for example, 700 °C or higher, depending on the material.

[0003] Japanese Patent No. 5910305 and Japanese Patent No. 5910306 disclose a hot press forming method having a step of heating a plurality of stacked conductive plate-shaped workpieces by attaching electrodes thereto and energizing them. The plurality of heated plate-shaped workpieces are arranged at a predetermined press position different from the energization position. The plurality of plate-shaped workpieces arranged at the press position are each press-formed. By simultaneously heating the plurality of plate-shaped workpieces by energization, productivity is improved.

[0004] In the hot press working method disclosed in Japanese Patent Application Laid-Open No. 2019-177394, the first workpiece and the second workpiece are heated without overlapping each other, then carried between the upper die and the lower die, and the second workpiece is placed in a posture overlapping the first workpiece, and then the upper die is lowered to press. Before and after the pressing process, a mold is lowered independently of the upper die to plastically deform the first workpiece and the second workpiece. As a result, the overlapping portions of the first workpiece and the second workpiece are engaged with each other and do not shift. In addition, a loading device is disclosed which includes an arm for transporting the first workpiece and a holder for transporting the second workpiece.

[0005] In the above prior art, heat is dissipated during the conveyance of the workpiece, and the temperature of the workpiece decreases. As a result, when the workpiece is carried into the mold of the press machine, the required temperature of the workpiece cannot be maintained, and there is a possibility that the quenching of the press-formed product is not sufficient.

[0006] Therefore, Japanese Patent No. 5814669 discloses a hot press transfer device that holds and transfers a panel-shaped object to be transferred in a heated state between each process of a production line for performing hot press. The hot press transfer device transfers the object to be transferred in a heated state while covering it with a heat-insulating cover. Thereby, the object to be transferred during conveyance is maintained at the temperature required for quenching.

[0007] Further, the hot press forming apparatus disclosed in Japanese Patent No. 4673656 has, as a heating device for a metal plate which is a workpiece to be processed, a primary heating means by induction heating or electric heating, and a secondary heating means by radiation heat transfer. The secondary heating means by radiation heat transfer is arranged in the transfer device from the primary heating means to the hot press forming die. By the secondary heating by radiation heat transfer, the metal plate can be uniformly heated, and the temperature deviation of the metal plate can be reduced.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

[0009] The inventors noticed that when the material for hot pressing is thinned, the temperature drop during the transfer of the heated material to the press machine can affect the quality of the press-formed product. Therefore, a method for suppressing the temperature drop of the material during transfer was investigated. In the investigation, it was found that it may be difficult to sufficiently suppress the temperature drop only by covering the material during transfer with a heat-insulating cover as in the above prior art. Also, it is conceivable to provide secondary heating means for heating the material during transfer. However, in this case, it is necessary to add equipment including a heat source for the secondary heating means on the transfer path. This may lead to an increase in the size of the equipment and an increase in equipment costs and operating costs.

[0010] Therefore, the present application discloses a method for manufacturing a press-formed product that can efficiently alleviate the temperature drop of a heated workpiece during the time it is transferred to the press-forming position. [Means for Solving the Problems]

[0011] The manufacturing method of a press-formed product according to an embodiment of the present invention includes a heating step of simultaneously heating at least two plate-shaped workpieces by a heating device, a conveying step of conveying the two heated workpieces heated in the heating step to a press machine, and a pressing step of processing the two heated workpieces conveyed to the press machine in the conveying step by the press machine. In the conveying step, the two heated workpieces are held in a state facing each other. At at least a part of an end of a first heated workpiece among the two heated workpieces, an end portion region including the end of the first heated workpiece has a shape bent toward the second heated workpiece, and a distance in the facing direction of the two heated workpieces between the end of the first heated workpiece and the second heated workpiece is smaller than a maximum interval in the facing direction of the two heated workpieces.

Advantages of the Invention

[0012] According to the present disclosure, during the conveyance time from after heating the material in press forming until starting the press forming, the temperature drop of the heated workpiece can be efficiently alleviated.

Brief Description of the Drawings

[0013]

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Embodiments for Carrying Out the Invention

[0014] In press forming, the temperature at the start of press forming depends on the heating temperature of the material and how much the temperature drops within the time it takes to transport the material to the mold for press forming after heating. The heating temperature of the material is determined by metallurgical conditions. Also, the transport time to the mold after heating is determined by the equipment configuration and specifications. The amount of temperature drop during that transport depends on the heat capacity of the material. For example, in the case of a steel plate, heat escapes mainly through heat transfer from the front and back surfaces to the atmosphere and heat radiation. The inventors have found that the amount of temperature drop depends greatly on the thickness of the material. That is, as described above, when the thickness of the material becomes thinner, even with the same transport time, the amount of temperature drop increases, and it may become difficult to ensure the forming start temperature required for quenching. As a result, the component strength required for the press-formed product may not be obtained.

[0015] The inventors considered a method of suppressing the temperature drop during transport without adding a heat source. As a result of the consideration, they came up with a configuration in which a plurality of plate-shaped materials (heated workpieces) heated simultaneously are transported simultaneously in a state facing each other. With this configuration, the facing heated workpieces can receive each other's radiant heat and compensate for the amount of heat. Furthermore, in the space between the facing heated workpieces, a heat retention effect can be obtained due to the air warmed by heat transfer from both heated workpieces remaining. As a result, the temperature drop during transport can be alleviated.

[0016] Through further consideration, the inventors came up with a configuration in which an end region including at least one end of two heated workpieces during transport has a shape bent in the direction of the other facing heated workpiece. As a result, it has been found that the temperature drop of the heated workpiece can be efficiently alleviated. The following embodiments are based on this finding.

[0017] A method for manufacturing a press-formed product according to an embodiment of the present invention is a heating step of simultaneously heating at least two plate-shaped workpieces by a heating device, a transport step of transporting the two heated workpieces heated in the heating step to a press machine, A pressing step of processing the two heated workpieces conveyed to the press machine in the conveying step with the press machine. In the conveying step, The two heated workpieces are held in a state of facing each other, In at least a part of the end of the first heated workpiece among the two heated workpieces, the end portion region including the end of the first heated workpiece has a shape bent toward the second heated workpiece, and the distance in the facing direction of the two heated workpieces between the end of the first heated workpiece and the second heated workpiece is smaller than the maximum interval in the facing direction of the two heated workpieces.

[0018] According to the above manufacturing method, during conveyance, in at least a part of the end of the first heated workpiece, the end portion region including the end has a shape bent toward the second heated workpiece, and the distance between the end of the first heated workpiece and the second heated workpiece becomes smaller. That is, the end portion region of the first heated workpiece includes a shape in which the distance to the second heated workpiece becomes closer as it approaches the end. Thereby, it is possible to reduce the amount of heat that escapes without reaching the opposing surfaces among the radiant heat radiated from the end portion regions of the two heated workpieces, and it becomes difficult for the heated stagnant air in the space sandwiched between the two heated workpieces to escape. Therefore, it is possible to efficiently mitigate the overall temperature drop including the end portion region of the heated workpiece during the time of conveying the heated workpiece to the press forming position.

[0019] The state in which the two heated workpieces face each other during conveyance is a state in which the plate surface (a surface other than the side surface (that is, the end surface)) of the first heated workpiece faces the plate surface (a surface other than the side surface) of the second heated workpiece. When there is a portion where the plate surfaces of the two heated workpieces facing each other are parallel, the direction perpendicular to the parallel plate surfaces is defined as the facing direction. When there is no portion parallel to the plate surfaces of the two heated workpieces, the normal direction to the plate surface at the center of gravity of the first heated workpiece is defined as the facing direction. When there are a plurality of portions parallel to the plate surfaces of the two heated workpieces, the direction perpendicular to the plate surface of the portion having the largest plate surface area among the parallel portions is defined as the facing direction.

[0020] When viewed from the opposing direction of the two heating workpieces, at least a part of the first heating workpiece overlaps with the second heating workpiece. From the perspective of alleviating temperature drop, it is preferable that in both the first heating workpiece and the second heating workpiece, 70% or more, preferably 80% or more, overlaps with the other opposing heating workpiece when viewed from the opposing direction.

[0021] In the first heating workpiece and the second heating workpiece, the end region is a region including the vicinity of the ends of the workpiece. A region within a certain distance from the end of the workpiece may be used as the end region. For example, in the direction perpendicular to the opposing direction, a portion at a distance of 20% of the dimension of the workpiece from the end of the workpiece may be used as the end region.

[0022] The opposing direction of the two heating workpieces is not limited to this, but may be, for example, the vertical direction (i.e., the direction of gravity). In this case, the two heating workpieces are conveyed in a state of overlapping in the vertical direction.

[0023] In the conveying step, at both ends of the first heating workpiece in at least one direction perpendicular to the opposing direction, it has a shape bent towards the second heating workpiece in the end region including the end of the first heating workpiece, and the distance in the opposing direction between the end of the first heating workpiece and the second heating workpiece may be smaller than the maximum interval. Thereby, the temperature drop of the heating workpiece can be alleviated more efficiently. Note that the distance in the opposing direction between the second heating workpiece and only one of the two ends of the first heating workpiece in the direction perpendicular to the opposing direction may be smaller than the maximum interval. In this case as well, the effect of improving the efficiency of alleviating temperature drop can be obtained.

[0024] For example, the distance from the second heating workpiece may be smaller than the maximum interval in the opposing direction of the two heating workpieces at both the end region of one end and the end region of the other end among the two ends of the first heating workpiece in at least one direction perpendicular to the opposing direction. In this case, there may be a portion where the interval in the opposing direction of the two heating workpieces is the largest between the one end and the other end.

[0025] In the conveying step, at least a part of the end of the second heating workpiece, an end region including the end of the second heating workpiece may have a shape bent toward the first heating workpiece. Thereby, the temperature drop of the heating workpiece can be more efficiently alleviated.

[0026] In the conveying step, the end region of the first heating workpiece including the end of the first heating workpiece where the distance from the second heating workpiece is smaller than the maximum interval may include an inclined portion inclined toward the second heating workpiece with respect to a virtual plane perpendicular to the facing direction. Thereby, the amount of heat that escapes without reaching the second heating workpiece among the radiant heat radiated from the inclined portion can be efficiently reduced.

[0027] In the conveying process, it is preferable that the angle between the inclined portion of the end region of the first heating workpiece and the portion including the end of the second heating workpiece closest to the inclined portion is 20° or more. Thereby, the temperature drop of the heating workpiece can be more effectively alleviated. From the same viewpoint, the above angle is more preferably 40° or more, and even more preferably 60° or more. Note that the end of the second heating workpiece closest to the inclined portion of the first heating workpiece is the end of the second heating workpiece at the position where the distance from the inclined portion of the first heating workpiece is the smallest. When both the plate surface of the inclined portion of the first heating workpiece and the plate surface of the portion including the end of the second heating workpiece closest to this inclined portion are flat surfaces, the angle between these flat surfaces or the virtual planes extending them is the angle between the inclined portion of the first heating workpiece and the portion of the second heating workpiece described above. When the portion of the second heating workpiece includes an inclined portion that inclines toward the first heating workpiece with respect to a virtual plane perpendicular to the facing direction, the above angle is determined based on the plane of the plate surface of the inclined portion of the second heating workpiece or the virtual plane extending it. When the plate surface of the inclined portion of the first heating workpiece is a curved surface, the above angle is determined based on the virtual plane that contacts the plate surface at the position closest to the end of the first heating workpiece on the plate surface of the inclined portion. When the plate surface of the portion including the end of the second heating workpiece closest to the inclined portion of the first heating workpiece includes a curved surface, the above angle is determined based on the virtual plane that contacts the plate surface at the position closest to the end of the second heating workpiece on the curved surface. Note that in the inclined portion of the first heating workpiece, when the plate surface on the inner side in the facing direction, that is, the plate surface facing the second heating workpiece, and the plate surface on the outer side in the facing direction on the back side thereof, that is, the plate surface on the side opposite to the second heating workpiece, are not parallel, the above angle is determined based on the plate surface on the inner side in the facing direction. Also in the second heating workpiece, in the portion including the end closest to the inclined portion of the first heating workpiece, when the plate surface on the inner side in the facing direction (the plate surface facing the first heating workpiece) and the plate surface on the outer side in the facing direction (the plate surface on the side opposite to the first heating workpiece) are not parallel, the above angle is determined based on the plate surface on the inner side in the facing direction.

[0028] In the conveying step, an end region including an end of the second heating workpiece facing the inclined portion of the end region of the first heating workpiece may include an inclined portion inclined toward the first heating workpiece side with respect to a virtual plane perpendicular to the facing direction. Thereby, the amount of heat that is radiated from the inclined portion of the second heating workpiece and escapes without reaching the first heating workpiece can be more efficiently reduced.

[0029] In the conveying step, the distance in the facing direction between the end of the first heating workpiece that is smaller than the maximum distance and the second heating workpiece is preferably 30 mm or less. Thereby, the temperature drop of the heating workpiece can be more effectively alleviated. From the same viewpoint, the above distance is more preferably 20 mm or less, and even more preferably 10 mm or less. Note that the maximum distance in the facing direction between the first heating workpiece and the second heating workpiece is not particularly limited, but from the viewpoint of alleviating the temperature drop, a smaller value is preferable. The maximum distance is preferably, for example, 300 mm or less, more preferably 200 mm or less, and even more preferably 100 mm or less.

[0030] In the conveying step, the two heating workpieces may be conveyed by a conveying device. In this case, the conveying step driving a pair of first arms rotatably attached to a base frame provided in the conveying device, and supporting and lifting the lower surfaces of both ends of the first heating workpiece with the claws of the pair of first arms; driving a pair of second arms rotatably attached to the base frame provided in the conveying device, and supporting and lifting the lower surfaces of both ends of the second heating workpiece with the claws of the pair of second arms; conveying the first heating workpiece supported by the lower surfaces of both ends by the claws of the pair of first arms of the conveying device and the second heating workpiece supported by the lower surfaces of both ends by the claws of the pair of second arms in a state where they face each other; driving the pair of first arms to lower the first heating workpiece supported by the pair of first arms to the press position (first press position) of the press machine; A step of driving the pair of second arms to lower the second heating work supported by the pair of second arms to the press position (second press position) of the press machine may be included.

[0031] Thereby, with a simple device configuration, the first heating work and the second heating work can be conveyed in a state where they can efficiently receive heat radiation from each other. Since both ends of the first heating work and the second heating work are supported by the first claws and the second claws respectively, the distance between both ends of the two works can be stably maintained. Therefore, it is possible to convey simply and efficiently while suppressing the temperature drop of the first and second heating works.

[0032] In the above manufacturing method, the pair of first arms of the conveying device may be driven by a system different from that of the pair of second arms. The first press position may be a position different from the second press position.

[0033] In the conveying step, one of the first heating work and the second heating work is placed on at least three first support columns extending upward from a tray body having a hollow portion penetrating vertically when viewed from above, and the other heating work of the first heating work and the second heating work is placed on at least three second support columns extending upward from the tray body, and may be conveyed together with the tray body in a state of being vertically overlapped with the one heating work above the one heating work.

[0034] In the above manufacturing method, after heating, the first heating workpiece and the second heating workpiece are conveyed together with the tray from the heating device to the lifting position. Therefore, after exiting the heating device, for example, until being lifted by the conveying device, the first heating workpiece and the second heating workpiece are in a state of overlapping vertically, that is, in the vertical direction. Also, one heating workpiece is placed on the first support column group, and the other heating workpiece placed on the second support column group is arranged above it. The support column group is formed to extend upward from the tray body. Therefore, for example, when lifting the second heating workpiece and the first heating workpiece placed on the support column group upward sequentially or simultaneously by the conveying device, the support column group does not become an obstacle. The lifting operation can be performed simply and quickly. As a result, it is possible to convey simply and efficiently while suppressing the temperature drop of the first and second heating workpieces.

[0035] In the above manufacturing method, in the heating step, similar to the conveying step, the one heating workpiece is placed on at least three first support column groups extending upward from the tray body, and the other heating workpiece is placed on at least three second support column groups extending upward from the tray body, and may be heated in a state of being vertically overlapped with the one heating workpiece above the one heating workpiece. Thereby, the two heating workpieces can be conveyed while being placed on the tray body in the state of the heating step.

[0036] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals and their description will not be repeated. The dimensional ratios between the constituent members shown in each drawing do not necessarily indicate the actual dimensional ratios.

[0037] (Embodiment 1) FIG. 1 is a diagram showing an outline of a press manufacturing line 10 used in a method for manufacturing a press-formed product according to the present embodiment. In FIG. 1, for the sake of explanation, an xyz orthogonal coordinate system with the vertical direction as the z direction is defined. The vertical direction is the same as the direction of gravity. The press manufacturing line 10 includes a heating device 14, a conveying table 16, a conveying device 46, a manipulator 44, a press machine 20, and a controller 22.

[0038] In the heating device 14, two heated workpieces W1 and W2 are heated simultaneously. The heated workpieces W1 and W2 are conveyed to the lifting position RM on the conveying table 16. At the lifting position RM, the workpieces W1 and W2 are lifted by the conveying device 46 and conveyed to the pressing position of the press 20. The lifting position RM is preferably a position close to the outlet 14A of the heating device 14. The conveying device 46 holds the workpieces W1 and W2 in a state facing each other and conveys them from the lifting position RM to the pressing position of the press 20. The press 20 press-forms the workpieces W1 and W2. Thereby, the workpieces W1 and W2 are processed into press-formed products.

[0039] FIG. 2 is a diagram showing an example of the heated workpieces W1 and W2 being conveyed by the conveying device 46 shown in FIG. 1. As shown in FIG. 2, in the conveyance of the heated workpieces W1 and W2, the two heated workpieces W1 and W2 are held in a state of overlapping in the vertical direction. The two heated workpieces W1 and W2 are conveyed in a state facing each other. In this example, the facing direction is, as an example, the same as the vertical direction. Also, at least a part of the end of the first heated workpiece W1 among the two heated workpieces W1 and W2 has a shape in which the end portion region including the end is bent toward the second heated workpiece W2. Further, at least a part of the end of the first heated workpiece W1, the distance D in the facing direction from the second heated workpiece W2 is smaller than the maximum interval Dmax in the facing direction of the two heated workpieces W1 and W2. That is, at least a part of the end of the first heated workpiece W1, the end portion region including the end includes a portion that is not parallel to the portion of the second heated workpiece W2 facing it. In the example of FIG. 2, in the region inside the end portion region on the plate surface of the first heated workpiece W1, the plate surface of the first heated workpiece and the plate surface of the second heated workpiece facing it are parallel.

[0040] In this way, by conveying the heating workpieces in a state where the end regions of the two heating workpieces are arranged to approach each other, it is possible to reduce the amount of heat that escapes without reaching the surface of the opposing heating workpiece among the radiant heat radiated from the end regions of the heating workpieces W1 and W2. FIG. 3 is a diagram showing the radiant heat of the heating workpieces W1 and W2 in the state shown in FIG. 2. FIG. 4 is a diagram showing the radiant heat in a state where flat heating workpieces are opposed to each other. As shown in FIG. 3, by bending and inclining the end region of one of the heating workpieces W1 and W2 inward, it is possible to increase the radiant heat reaching the other opposing heating workpiece. That is, as shown in FIG. 4, in a state where flat heating workpieces without inclination of the end region are stacked, a part of the heat radiated from the end region of the heating workpiece (for example, the radiant heat in the directions of the arrows N1 and N2 in FIG. 4) does not reach the opposing heating workpiece and escapes. In the example of FIG. 3, due to the inclination of the end regions of the heating workpieces W1 and W2, it is possible to reduce the radiant heat that escapes without reaching the heating workpiece. Also, the heated stagnant air in the space sandwiched between the two heating workpieces W1 and W2 is less likely to escape to the outside of the space. As a result, during the conveyance of the heating workpieces W1 and W2, the temperature drop can be efficiently alleviated.

[0041] In the example of FIG. 2, the end region of the first heating workpiece W1 bends toward the second heating workpiece W2, and the end region of the second heating workpiece W2 bends toward the first heating workpiece W1. In this way, by conveying in a state where the end regions of the two heating workpieces W1 and W2 are inclined so as to approach each other, the effect of alleviating the temperature drop can be easily obtained.

[0042] Specifically, the end region of the first heating workpiece W1 includes an inclined portion W1k that is inclined toward the second heating workpiece with respect to a virtual plane perpendicular to the opposing direction. Similarly, the end region of the second heating workpiece W2 also includes an inclined portion W2k that is inclined toward the first heating workpiece with respect to a virtual plane perpendicular to the opposing direction. In this way, inclined portions that approach each other as they approach the ends are provided in both the end region of the first heating workpiece W1 and the end region of the second heating workpiece W2 that oppose each other. Thereby, heat radiation and leakage of stagnant air can be effectively suppressed.

[0043] The angle θ1 between the inclined portion W1k of the end region of the first heating workpiece W1 and the inclined portion W2k which is an example of the portion including the end of the second heating workpiece W2 closest to the inclined portion W1k is not limited to this, but can be 20° or more (θ1 ≧ 20°). Thereby, the temperature drop can be effectively alleviated. From this viewpoint, θ1 ≧ 40° is more preferable, and θ1 ≧ 60° is even more preferable.

[0044] In the example of FIG. 2, the inclined portions W1k and W2k of the first heating workpiece W1 and the second heating workpiece W2 are flat plate-shaped, but the inclined portions W1k and W2k may have a curved shape such that the plate surface is a curved surface. For example, the inclined portions W1k and W2k may have a curvature (R). Note that the form in which the inclined portion is curved is not limited to the form in which the curvature is constant in the inclined portion.

[0045] From the viewpoint of enhancing the effect of alleviating the temperature drop, the distance D in the facing direction between the end of the first heating workpiece W1 and the second heating workpiece W2 is preferably small. Although not limited to these, for example, the distance D is preferably D ≦ 30 mm, more preferably D ≦ 20 mm, and even more preferably D ≦ 10 mm.

[0046] In the example of FIG. 2, at both ends in the x direction which is the direction perpendicular to the facing direction of the first heating workpiece W1, the distance D in the facing direction from the second heating workpiece W2 is smaller than the maximum interval Dmax (D < Dmax). In this way, by making the distance between the two heating workpieces small at both ends in the direction perpendicular to the facing direction, the stagnant air heated between the first heating workpiece W1 and the second heating workpiece W2 is less likely to leak from the space between the heating workpieces. Also, in the example of FIG. 2, inclined portions W1k are provided in the end regions at both ends in the x direction of the first heating workpiece W1. By providing inclined portions at the end regions at both ends, the amount of heat that escapes without reaching the opposing heating workpiece among the radiant heat from the end regions at both ends is reduced. In the example of FIG. 2, inclined portions W2k are also provided at both ends in the x direction of the second heating workpiece W2.

[0047] In the example of FIG. 2, the shapes of the inclined portions in the end regions at both ends in the direction perpendicular to the facing direction of the first heating workpiece W1 are the same. In contrast, the shapes of these inclined portions at both ends (for example, the inclination angle, dimensions, or curvature, etc.) may be different from each other.

[0048] Note that the inclined portions of the first heating workpiece W1 or the second heating workpiece W2 may be provided in the end regions at both ends in two directions perpendicular to each other within a virtual plane perpendicular to the facing direction, for example, the x-direction and the y-direction. Thereby, the effect of alleviating the temperature drop can be enhanced more. Also, the two heating workpieces W1, W2 may be arranged so that D < Dmax over the entire circumference of the end of the first heating workpiece W1.

[0049] FIG. 5 is a perspective view showing an example in which inclined portions are provided in the end regions at both ends in the x-direction of the first heating workpiece W1, and no inclined portions are provided in the end regions at both ends in the y-direction. In the example of FIG. 5, in a part of the end of the first heating workpiece W1, the end region has a shape bent toward the second heating workpiece. FIG. 6 is an example in which inclined portions are provided in the end regions at both ends in the x-direction and the y-direction of the first heating workpiece W1. In the example of FIG. 6, over the entire end of the first heating workpiece W1, the end region has a shape bent toward the second heating workpiece.

[0050] Figs. 7 to 11 are diagrams showing modified examples of the arrangement of the first heating workpiece W1 and the second heating workpiece W2 in the conveying process. In the example of Fig. 7, inclined portions W1k are provided in the end regions at both ends in one direction (for example, the x direction) perpendicular to the facing direction of the first heating workpiece W1. The second heating workpiece W2 is a flat plate. Also in this case, the distance D in the facing direction between each of the two ends in the x direction of the first heating workpiece W1 and the second heating workpiece W2 satisfies D < Dmax. In the example of Fig. 7, the end of the first heating workpiece W1 is at a position overlapping in the facing direction with the end of the second heating workpiece W2. On the other hand, the end of the first heating workpiece W1 and the end of the second heating workpiece W2 may not overlap in the facing direction. For example, when viewed from the facing direction, the end of the second heating workpiece W2 may be located inside the end of the first heating workpiece W1. In such a case, the distance in the facing direction between the virtual plane obtained by extending the plate surface on the inner side in the facing direction of the second heating workpiece W2 and the end of the first heating workpiece W1 is defined as the distance D in the facing direction between the end of the first heating workpiece W1 and the second heating workpiece W2.

[0051] In the example of Fig. 8, an inclined portion W1k is provided in the end region of one end out of the two ends in one direction (for example, the x direction) perpendicular to the facing direction of the first heating workpiece W1. The end region of the second heating workpiece W2 facing the inclined portion W1k has no inclined portion and extends in the horizontal direction. An inclined portion W2k is provided in the end region of one end out of the two ends in the direction (x direction) perpendicular to the facing direction of the second heating workpiece W2. The end of the first heating workpiece W1 facing the inclined portion W2k has no inclined portion and extends in the horizontal direction. Also in this case, the distance D in the facing direction between each of the two ends in the x direction of the first heating workpiece W1 and the second heating workpiece W2 satisfies D < Dmax. In this way, the heating workpieces W1 and W2 may be conveyed in a state where inclined portions are arranged on one of the facing end regions of the two heating workpieces W1 and W2 and no inclined portion is arranged on the other. Note that Fig. 8 is an example of a case where the end region is bent toward the second heating workpiece at a part of the end of the first heating workpiece. Also in the examples of Figs. 7 and 8, the preferable range of the angle θ1 between the inclined portion W1k of the first heating workpiece W1 and the portion including the end of the second heating workpiece W2 closest to the inclined portion W1k is the same as in the case of Fig. 2 above.

[0052] In the example of FIG. 9, the inclined portions W1k of the first heating workpiece W1 and the inclined portions W2k of the second heating workpiece W2 both extend at right angles to a virtual plane perpendicular to the opposing direction. The angle θ1 between the inclined portion W1k of the first heating workpiece W1 and the portion (inclined portion W2k) including the end of the second heating workpiece W2 closest to the inclined portion W1k is θ1 = 180°. Thus, the angle θ1 may be θ1 = 180°. However, to increase the angle θ1, it is necessary to increase the angle at which the workpiece is bent. In this case, the processing cost of the workpiece tends to be high. From the viewpoint of workability, θ1 ≤ 180° is preferable, θ1 ≤ 160° is more preferable, and θ1 ≤ 140° is even more preferable. Note that the inclined portions of the heating workpieces W1 and W2 may be processed into a desired product shape through a hot pressing process. In this case, the angle θ1 of the inclined portion can be set to an appropriate angle so as to be easily press-formed into the target product shape.

[0053] In the example of FIG. 9, both ends of the first heating workpiece W1 in the x direction are in contact with the second heating workpiece W2. Thus, the heating workpieces W1 and W2 may be conveyed in a state where at least a part of the end of the first heating workpiece W1 is in contact with the second heating workpiece W2. Thereby, the effect of mitigating the temperature drop can be further enhanced.

[0054] In the example of FIG. 10, the first heating workpiece W1 and the second heating workpiece W2 are formed to have a convex shape in which the central portions protrude in the same direction in the plate thickness direction and a shape in which the end regions are bent in a direction approaching each other. Thus, the two intermediate-formed workpieces can be conveyed in a state where they face each other as the first heating workpiece W1 and the second heating workpiece W2. In the example of FIG. 10, the first heating workpiece W1 and the second heating workpiece W2 are hat-shaped members. A part of the flange of the hat-shaped member serves as the inclined portions W1k and W2k. As a modification, the entire flange of the hat-shaped member may be the inclined portions W1k and W2k. Note that the hat-shaped member is a member having a top plate, a pair of vertical walls extending from both ends of the top plate, and a flange extending from the end opposite to the top plate of the vertical wall.

[0055] In the example of FIG. 11, the first heating workpiece W1 and the second heating workpiece W2 are curved so as to have a curvature (R) as a whole. Therefore, the inclined portions W1k and W2k in the end regions of the first heating workpiece W1 and the second heating workpiece W2 have the curvature (R). The plate surfaces of the inclined portions W1k and W2k are curved surfaces. Thus, the first heating workpiece W1 may have a shape that is bent as a whole such that the central portion protrudes outward in the facing direction. When the inclined portions in the end regions of the first heating workpiece W1 or the second heating workpiece W2 have a curvature, for example, as shown in FIG. 11, a virtual plane that contacts the plate surface at a position closest to the end of the first heating workpiece on the plate surface of the inclined portion of the first heating workpiece W1, and a virtual plane that contacts the plate surface of the second heating workpiece W2 at a position closest to the end of the second heating workpiece on the plate surface of the inclined portion of the second heating workpiece W2, the angle between them is defined as angle θ1. In the examples of FIGS. 10 and 11, the preferable range of the angle θ1 is the same as that in the case of FIG. 2 above.

[0056] The two heating workpieces W1 and W2 shown in FIGS. 2, 5 to 11 above can be formed by bending a metal plate, except for the second heating workpiece W2 in FIG. 7. In the present embodiment, in the heating device 14, the bent first heating workpiece W1 and second heating workpiece W2 are heated. That is, the bending process of the workpiece is performed before heating. The bending process of the workpiece is performed, for example, by press forming.

[0057] (Specific example of press production line) An example of the device configuration of the press production line 10 shown in FIG. 1 will be described below. The press production line 10 is, as an example, a hot press production line. In the example shown in FIG. 1, a transfer table 16 is arranged on the path from the heating device 14 to the press 20. The end of the transfer table 16 is connected to the outlet 14A of the heating device 14. The inlet 14B of the heating device 14 may be connected to, for example, another transfer table (not shown). A part of the transfer table 16 is at the lifting position RM.

[0058] (Heating device) The heating device 14 is a device that heats an object to be heated (workpiece). Examples of the heating device 14 include a resistance heating furnace, a gas heating furnace, a far-infrared heating furnace, and a near-infrared heating furnace. 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 a direct-current heating device that directly energizes the object to be heated for heating. The heating device 14 may have a heating chamber. The heating device 14 may be provided inside the heating chamber with a plurality of indoor rollers that are rotationally driven by a drive mechanism (not shown). By rotating the indoor rollers, the object to be heated on the indoor rollers is conveyed.

[0059] (Conveyor table) The conveyor table 16 is provided with a plurality of conveyor rollers 26 that are rotationally driven by a drive mechanism (not shown). By each conveyor roller 26 rotating in synchronization with the indoor rollers, the object to be conveyed (heated workpiece) can be conveyed between the conveyor table 16 and the heating chamber of the heating device 14. The plurality of conveyor rollers 26 are arranged at intervals. The conveyor table 16 is an example of a table on which the heated workpiece heated by the heating device is placed. Also, the conveyor table 16 is an example of a conveyance path that conveys the heated workpiece from the heating device to the lifting position. Note that the configuration of the conveyance path is not limited to the conveyor table 16 shown in FIG. 1. For example, the conveyance path may be a belt conveyor or a rail, etc. Also, in the example shown in FIG. 1, the lifting position is on the conveyance path, but the lifting position may not be on the conveyance path. A table serving as the lifting position may be provided separately from the conveyance path.

[0060] (Press machine) The press 20 includes a lower die and an upper die for press-forming a workpiece to be pressed. The lower die is configured as a punch die as an example, and the upper die is configured as a die die as an example. A refrigerant flow path may be provided in the upper die and the lower die. Thereby, the heat taken from the workpiece during pressing can be released via the refrigerant. Two heating workpieces can be arranged between the upper die and the lower die. The upper die and the lower die are relatively movable. The press 20 presses the two heating workpieces by relatively approaching the upper die and the lower die in a state where the two heating workpieces are arranged between the upper die and the lower die. The operations of the upper die and the lower die can be controlled by, for example, the controller 22. In this example, the lower die and the upper die of the press 20 are shaped such that a plurality of press-formed products can be manufactured simultaneously. This is an example of the case where two pairs of dies are provided in one press. In this example, a plurality of workpieces are arranged between the lower die and the upper die of the press 20, and the plurality of workpieces are pressed simultaneously. Note that a plurality of presses may be provided. For example, two presses each having a pair of dies may be provided.

[0061] (Manipulator) The manipulator 44 transports the object to be transported between the transport table 16 and the press 20 using the transport device 46. The transport device 46 performs operations of lifting, holding, and placing the workpiece that is the object to be transported. The manipulator 44 controls the position and posture of the transport device 46. The transport device 46 may be an end effector of the manipulator 44. The manipulator 44 moves the transport device 46 between a position above the transport table 16 and a position between the two pairs of dies (upper die and lower die) of the press 20. The manipulator 44 includes a base rotatable about at least one axis and an arm extending from the base and having at least one joint. The transport device 46 is rotatably attached to the tip of the arm. Note that the moving device for moving the transport device 46 is not limited to a manipulator. For example, the moving device may be configured to include a rail connecting between the transport table 16 and the press 20 and a suspension device that suspends the transport device 46 movably up and down on the rail.

[0062] (Controller) The controller 22 controls the heating device 14, the transfer table 16, the press 20, and the manipulator 44. The controller 22 is configured as a control system including at least one computer, for example. As an example, the controller 22 may include control units (for example, configured by circuits or processors) provided in each of the heating device 14, the transfer table 16, the manipulator 44, and the press 20 to control each device. In this case, the controller 22 may include an overall control computer that supplies control information to the control units of each device and controls the overall operation of the press production line 10. The operation of the arm of the transfer device 46 described later may be controlled by a part of the controller 22, for example, the control unit of the manipulator 44.

[0063] (Transfer Device) FIG. 12 is a side view showing a configuration example of the transfer device 46 in FIG. 1 as viewed from the lateral direction (y direction). FIG. 13 is a view showing a state in which the second arm 72 of the transfer device 46 in FIG. 12 is opened outward. FIG. 14 is a side view showing a configuration example of the transfer device 46 in FIG. 1 as viewed from the lateral direction (x direction). In FIGS. 12 to 14, an example in which the first heating workpiece W1 is stacked on the second heating workpiece W2 is shown.

[0064] (Base Frame) In the example shown in FIGS. 12 and 13, the transfer device 46 includes a base frame 48, a pair of first arms 71 rotatably attached to the base frame 48, and a pair of second arms 72. The shape of the base frame 48 is rectangular when viewed from above. In this example, the vertical direction (perpendicular direction) is the z direction. The direction in the plane perpendicular to the vertical direction is the lateral direction. Among the lateral directions, the long side direction of the base frame 48 is the y direction, and the short side direction is the x direction.

[0065] A joint 56 connected to the manipulator 44 is provided on the upper surface of the base frame 48. The joint 56 is connected so that the base frame 48 can rotate about the vertical axis with respect to the manipulator 44.

[0066] (First arm and second arm) A pair of first arms 71 are arranged spaced apart in the lateral direction (x direction). Each of the pair of first arms 71 has a first base 71a extending vertically from the base frame 48 and a first claw 71b extending laterally and bent from the first base 71a. Each first arm 71 is attached to the base frame 48 so as to be rotatable about a rotation axis 60 in the y direction. One end of the first base 71a is rotatably connected to the base frame 48, and the first claw 71b extends from the other end.

[0067] A pair of second arms 72 are arranged spaced apart in the lateral direction (x direction). Each of the pair of second arms 72 has a second base 72a extending vertically from the base frame 48 and a second claw 72b extending laterally and bent from the second base 72a. Each second arm 72 is attached to the base frame 48 so as to be rotatable about a rotation axis 60 in the y direction. One end of the second base 72a is rotatably connected to the base frame 48, and the second claw 72b extends from the other end.

[0068] The positions of the pair of first claws 71b in the vertical direction and the positions of the pair of second claws 72b in the vertical direction are different from each other. In the examples shown in FIGS. 12 and 13, in the vertical direction, the first base 71a is shorter than the second base 72a. The first claw 71b is closer to the base frame 48 than the second claw 72b.

[0069] In the examples shown in FIGS. 12 and 13, the rotation axis 60 of the first arm 71 and the rotation axis 60 of the second arm 72 are coaxial. Thereby, the first arm 71 and the second arm 72 can be efficiently arranged on the base frame 48. Note that the rotation axis 60 of the first arm 71 and the rotation axis 60 of the second arm 72 do not have to be coaxial.

[0070] (Drive unit) The pair of second arms 72 are driven by a second drive unit. The second drive unit changes the lateral (x-direction) distance between the pair of second claws 72b by rotating the pair of second arms 72 with respect to the base frame 48. In the example shown in FIGS. 12 and 13, the second drive unit is composed of an actuator 82 provided for each second arm 72.

[0071] The actuator 82 is, for example, an air cylinder. The actuator 82 adjusts the amount of extension of the operating shaft 82A that moves in the axial direction. A pin 82B is provided at the end of the operating shaft 82A. The pin 82B is movably and rotatably inserted into the long hole of a link 90 fixed to the second arm 72.

[0072] When each actuator 82 extends the operating shaft 82A, as shown in FIG. 12, the corresponding second arm 72 extends downward, and the pair of second claws 72b of the pair of second arms 72 are in a closed state where they approach each other. Also, when each actuator 82 retracts the operating shaft 82A, as shown in FIG. 13, the pair of second claws 72b of the pair of second arms 72 move apart from each other to an open state.

[0073] The pair of first arms 71 are driven by a first drive unit. The first drive unit changes the lateral (x-direction) distance between the pair of first claws 71b by rotating the pair of first arms 71 with respect to the base frame 48. The first drive unit that drives the first arm 71 can also be configured to include, for example, an actuator similar to the actuator 82 shown in FIGS. 12 and 13. The pair of first arms 71 are also controlled by the first drive unit such that the pair of first claws 71b are in a closed state where they approach each other (see FIG. 12), or an open state where the pair of first claws 71b are farther apart from each other than in the closed state. Note that the actuators of the first drive unit and the second drive unit are not limited to air cylinders, and may be, for example, motors or hydraulic cylinders.

[0074] The pair of first claws 71b can support the lower surfaces of both lateral ends of the first heating work W1 in a state where they approach each other in the lateral direction, i.e., in a closed state. The pair of second claws 72b can support the lower surfaces of both lateral ends of the second heating work W2 in a state where they approach each other in the lateral direction, i.e., in a closed state.

[0075] (The third arm and the fourth arm) In the examples shown in FIGS. 12, 13, and 14, a pair of third arms 73 and a pair of fourth arms 74 are rotatably attached to the base frame 48. Although not shown, a third drive unit for driving the pair of third arms 73 and a fourth drive unit for driving the pair of fourth arms 74 are provided on the base frame 48. In FIG. 14, the illustration of the first to fourth drive units is omitted.

[0076] The pair of third arms 73 are arranged side by side in a direction (y direction) perpendicular to the direction (x direction) in which the pair of first arms 71 are arranged (see FIG. 14). Each third arm 73 is rotatably attached to the base frame 48 about a rotation axis 62 in a direction (x direction) perpendicular to the rotation axis 60 of the first arm. Each third arm 73 can be configured in the same manner as each first arm 71. Each third arm 73 has a third base 73a and a third claw 73b. The pair of third claws 73b and the pair of first claws 71b support the lower surface of the first heating work W1. In this example, the distance of the third claw 73b from the base frame 48 is different from the distance of the first claw 71b from the base frame 48. The distance of the third claw 73b from the base frame 48 can be determined according to the shape of the work to be supported.

[0077] A pair of fourth arms 74 are arranged side by side in a direction (y direction) perpendicular to the arrangement direction (x direction) of the pair of second arms 72 (see FIG. 14). Each fourth arm 74 is attached to the base frame 48 so as to be rotatable about a rotation axis 62 in a direction (x direction) perpendicular to the rotation axis 60 of the second arm. Each fourth arm 74 can be configured in the same manner as each second arm 72. Each fourth arm 74 has a fourth base 74a and a fourth claw 74b. The lower surface of the second heating work W2 is supported by the pair of fourth claws 74b and the pair of second claws 72b. In this example, the distance of the fourth claw 74b from the base frame 48 is different from the distance of the second claw 72b from the base frame 48. The distance of the fourth claw 74b from the base frame 48 can be determined according to the shape of the work to be supported.

[0078] (Control system) In this embodiment, as an example, the first arm 71 and the second arm 72 are driven by different systems. That is, the rotation of the first arm 71 and the rotation of the second arm 72 are controlled independently of each other. Also, the third arm 73 and the fourth arm 74 are driven by different systems. The first arm 71 and the third arm 73 are driven by the same system. The second arm 72 and the fourth arm 74 are driven by the same system. Note that the first arm 71 and the third arm 73 may be driven by different systems. The second arm 72 and the fourth arm 74 may also be driven by different systems.

[0079] (Conveying example using a tray) The first heating workpiece W1 and the second heating workpiece W2 may be placed on a tray in a vertically overlapping state and conveyed to the lifting position RM. FIG. 15 is a diagram showing a modified example of the press manufacturing line 10 in FIG. 1. In the press manufacturing line 10 shown in FIG. 15, two heating workpieces W1 and W2 are heated and conveyed using a tray. The tray 1 is a tray on which the first heating workpiece W1 and the second heating workpiece W2 are placed in the heating device 14 and the conveying table 16. The tray 1 has a tray body 2 and a column group 3 extending upward from the tray body 2. The column group 3 has a first column group for placing one of the two heating workpieces W1 and W2 and a second column group for placing the other heating workpiece. The first column group includes at least three columns configured to support the lower surface of one heating workpiece. The second column group includes at least three columns configured to support the other heating workpiece above the one heating workpiece supported by the first column group. The first column group is arranged such that a virtual straight line connecting the columns forms at least one triangle when viewed from above. The second column group is arranged at a position different from the first column group when viewed from above, and is arranged such that a virtual straight line connecting the columns forms at least one triangle when viewed from above. All of the second column group are higher than the lowest column of the first column group.

[0080] In the heating device 14, the second heating workpiece W2 is placed on the first column group, the first heating workpiece W1 is placed on the second column group, and is heated in a state of being overlapped above the second heating workpiece W2. The first heating workpiece W1 and the second heating workpiece W2 are conveyed from the heating device 14 to the lifting position by the conveying device 46 on the conveying table 16 in a state of being placed on the tray 1. As a result, the first and second heating workpieces W1 and W2 face each other during the period from after heating until they are lifted by the conveying device 46. Therefore, the temperature drop is alleviated.

[0081] At the lifting position on the transfer table 16, the second heating workpiece W2 placed on the first support column group and the first heating workpiece W1 placed on the second support column group are each supported by the second claw 72b of the second arm 72 and the first claw 71b of the first arm 71 of the transfer device 46, and may be simultaneously lifted upward and transferred to the respective pressing positions of the press 20 by the transfer device 46. At this time, the operation of driving the first arm 71 to arrange the pair of first claws 71b on the lower surface of the first heating workpiece W1 and the operation of driving the second arm 72 to arrange the pair of second claws 72b on the lower surface of the second heating workpiece W2 may be performed simultaneously or sequentially. By simultaneously lifting the first and second heating workpieces W1 and W2 placed on the tray 1 by the transfer device 46, the transfer time can be shortened and the temperature drop can be further reduced. Further, the first heating workpiece W1 placed on the second support column group is lifted upward by the first claw 71b of the first arm 71 of the transfer device 46, and then the second heating workpiece W2 placed on the first support column group is lifted by the second arm 72 of the transfer device 46, and each may be transferred to the pressing position of the press 20 by the transfer device 46. When the transfer device 46 lifts the second heating workpiece W2 placed on the first support column group and the first heating workpiece W1 placed on the second support column group of the support column group 3 upward simultaneously or sequentially, the support column group 3 does not become an obstacle.

[0082] The tray body 2 has a shape that extends vertically in the vertical direction and may include a hollow portion that penetrates vertically. Thereby, in the heating process, the heat from below the tray body 2 is easily transmitted to the first heating workpiece W1 and the second heating workpiece W2. The first support column group and the second support column group may be located between the hollow portions of the tray body 2 when viewed from above. Thereby, the heat from below the tray body 2 is easily transmitted to the second heating workpiece W2 placed on the first support column group and the first heating workpiece W1 placed on the second support column group through the hollow portions around the first support column group and the second support column group.

[0083] (Tray) FIG. 16 is a top view of the tray 1 as seen from above. FIG. 17 is a side view of the tray 1 shown in FIG. 16 as seen from the direction of arrow F. In the example shown in FIG. 16, the tray body 2 has a shape that extends along a plane perpendicular to the vertical direction and includes a hollow portion 2G that penetrates vertically. When viewed from above, the area of the hollow portion 2G is wider than the area of the constituent members of the tray body 2. The tray 1 has a plurality of support columns 3 (3a, 3b) that extend upward from the tray body 2. The plurality of support columns 3 include a first support column group 3a on which the second heating workpiece W2 can be placed and a second support column group 3b on which the first heating workpiece W1 can be placed above the second heating workpiece W2. Both the first support column group 3a and the second support column group 3b are located between the hollow portions 2G of the tray body 2 when viewed from above.

[0084] (Tray body) In the example shown in FIG. 16, the tray body 2 has a frame 2c and rod members 2f spanned inside the frame 2c. The frame 2c includes a pair of vertical frames 2b and a pair of horizontal frames 2a. The pair of vertical frames 2b are arranged in parallel at a lateral distance. The pair of horizontal frames 2a are arranged in parallel at a vertical distance between the pair of vertical frames 2b. The pair of vertical frames 2b and the horizontal frames 2a form a rectangular frame 2c when viewed from above. The rod members 2f include vertical rod members 2d and horizontal rod members 2e. The vertical rod members 2d are spanned between the pair of horizontal frames 2a. The horizontal rod members 2e are spanned between the pair of vertical frames 2b. The rod members 2f are arranged in a grid pattern within the frame 2c.

[0085] The rod member 2f (at least one of the vertical rod member 2d and the horizontal rod member 2e) may be configured to be position-adjustable in the frame 2c. For example, a plurality of positioning holes or locking pieces may be provided in the frame 2c. In this case, the rod member 2f is fixed to the holes or locking pieces of the frame 2c using a fastener or the like as necessary. By changing the position of the holes or locking pieces for fixing the rod member 2f, the position of the rod member 2f in the frame 2c can be adjusted.

[0086] The constituent members of the tray body 2 (in the example of Fig. 16, the frame 2c and the bar member 2f) may be pipe materials or solid materials. Further, the constituent members of the tray body 2 may be angle materials with an L-shaped cross section or channel materials with a U-shaped cross section. The material of the constituent members of the tray body 2 is not particularly limited, but is formed of a heat-resistant material, for example, heat-resistant steel or the like or ceramics or the like. The maximum use temperature of the constituent members is desirably in the range of 900 °C or higher, which is commonly used in the heating device, and 1050 °C or lower, which is the upper limit setting temperature of the heating device. Examples of the heat-resistant steel (heat-resistant alloy steel) that can be used as the constituent member include SCH22 (0.4C-25Cr-20Ni), SCH24 (0.4C-25Cr-35Ni-Mo,Si), and the like. If the constituent members of the tray body 2 are formed of heat-resistant alloy steel, processing and manufacturing become easy. Note that the materials that can be used as the constituent members of the tray body 2 described above can also be used as the materials of the support columns 3.

[0087] (Support column) The first support column group 3a includes at least three support columns in which virtual straight lines connecting the support columns form a triangle when viewed from above. The second support column group 3b includes at least three support columns in which virtual straight lines connecting the support columns form a triangle when viewed from above. All of the second support column groups 3b are arranged at positions different from those of the first support column group 3a when viewed from above. All of the second support column groups 3b are higher than the lowest support column among the first support column groups 3a. Thereby, the first support column group 3a and the second support column group 3b can support the first heating workpiece W1 and the second heating workpiece W2 in a vertically stacked state.

[0088] The second support column group 3b is arranged in a region where the other heating workpiece is placed when viewed from above and does not overlap with the region where one heating workpiece is placed. Further, the second support column group 3b is configured so as not to overlap with the region where one heating workpiece is placed when viewed from above. That is, the second support column group 3b is configured so that when one heating workpiece is lifted upward by the transfer device 46, the one heating workpiece is not caught by the second support column group 3b.

[0089] In the example shown in FIG. 16, one of the heating workpieces (the second heating workpiece W2 in this example) has a notch at the edge (end) when viewed from above. The second support column group 3b is arranged in a region corresponding to the notch of the second heating workpiece W2. In this way, by arranging the second support column group 3b in a region corresponding to the notch or hole of one of the heating workpieces, the second support column group 3b can be arranged in a region that does not overlap with one of the heating workpieces when viewed from above. Note that the configurations of the first support column group, the second support column group, and the heating workpiece are not limited to the example shown in FIG. 16. For example, the first heating workpiece W1 and the second heating workpiece W2 having the same shape may be arranged at shifted positions when viewed from above. In this case, the first heating workpiece W1 and the second heating workpiece W2 are arranged so that a part of the second heating workpiece W2 does not overlap with the first heating workpiece W1 when viewed from above. The second support column group 3b is arranged at a position in the region where the first heating workpiece W1 is arranged and that does not overlap with the region where the second heating workpiece W2 is arranged. In this case, it is not necessary to provide notches, holes, or the like in the second heating workpiece W2.

[0090] Referring to FIG. 17, the height of each of the first support column groups 3a is a height corresponding to the shape of one of the heating workpieces (the second heating workpiece W2 in this example), and the height of each of the second support column groups 3b is a height corresponding to the shape of the other heating workpiece (the first heating workpiece W1 in this example).

[0091] [Specific Example of the Manufacturing Process of the Press-Formed Product] An example of the process of manufacturing a press-formed product using the above-described press production line 10 will be described. The manufacturing process of the press-formed product in the present embodiment includes, as described above, a heating process for heating the workpiece, a conveying process for conveying the heating workpiece, and a pressing process for pressing the heating workpiece.

[0092] (Heating Process) In the heating process, at least two plate-shaped workpieces W1 and W2 are simultaneously heated by the heating device 14. Here, for the mode of simultaneously heating a plurality of workpieces, it is only necessary that the heating of the plurality of workpieces ends simultaneously, and the start of heating does not necessarily have to be simultaneous. Further, in addition to the case where the end points of heating of the plurality of workpieces are exactly simultaneous, the case where the end points are slightly deviated is also included in the mode of simultaneously heating the plurality of workpieces. For example, even if there is a deviation of about the time required for the operation of lifting the heated workpiece by the transfer device 46, from the viewpoint of the temperature drop of the workpiece being transferred, it can be regarded as being substantially simultaneous. The heated workpiece after heating is discharged out of the heating device 14 by the rotation of the roller 13 of the heating device 14 and the transfer roller 26 of the transfer table 16.

[0093] (Transfer process) As an example, the transfer process includes a process of transferring the first heated workpiece W1 and the second heated workpiece W2 from the heating device 14 to the lifting position, a process of the transfer device 46 lifting the first heated workpiece W1, a process of the transfer device 46 lifting the second heated workpiece W2, a process of transferring the first and second heated workpieces W1 and W2, a process of lowering the first heated workpiece W1 to the pressing position, and a process of lowering the second heated workpiece W2 to the pressing position.

[0094] An example of the process of the transfer device 46 lifting the first heated workpiece W1 is as follows. A pair of first arms 71 rotatably attached to the base frame of the transfer device 46 are driven, and the lower surfaces of both ends of the first heated workpiece W1 are supported and lifted by the claws of the pair of first arms 71. At this time, the pair of first arms 71 and the pair of second arms 72 are opened, and the transfer device 46 is lowered to approach the first heated workpiece W1 on the transfer roller 26 of the transfer table 16. By rotating the pair of first arms 71 to the closed state, the first claws of the pair of first arms 71 are made to dive below the lower surfaces of both ends of the first heated workpiece W1. In this state, by raising the transfer device 46, the lower surfaces of both ends of the first heated workpiece W1 are supported and lifted by the first claws of the pair of first arms 71.

[0095] An example of the process in which the transfer device 46 lifts the second heating workpiece W2 is as follows. While the transfer device 46 supports and holds the lower surface of the first heating workpiece W1 with a pair of first arms 71, the transfer device 46 drives a pair of second arms 72 to lift the second heating workpiece W2. Similar to the lifting operation of the first heating workpiece W1, the transfer device 46 supports and lifts the lower surfaces of both ends of the second heating workpiece W2 with the second claws of the pair of second arms 72.

[0096] The transfer device 46 conveys the first heating workpiece W1 supported on the lower surface by the first claws of the pair of first arms 71 and the second heating workpiece W2 supported on the lower surface by the second claws of the pair of second arms 72 in a state where they overlap each other in the vertical direction of the first heating workpiece W1, that is, in a state where they face each other. Then, the transfer device 46 moves, for example, to the press position of the second heating workpiece W2. While the transfer device 46 supports and holds the lower surface of the first heating workpiece W1 with a pair of first arms 71, the transfer device 46 drives the pair of second arms 72 to an open state and lowers the second heating workpiece W2 to the press position of the press 20. Thereafter, the transfer device 46 moves to the press position of the first heating workpiece W1, drives the pair of first arms 71 to an open state, and lowers the first heating workpiece W1 to the press position of the press 20.

[0097] [Material of the heating workpiece] The material of the heating workpiece may be a formable metal. Examples of the material of the heating workpiece include, but are not limited to, carbon steel and stainless steel of the Fe series, Al series, and Ti series materials. Further, the heating workpiece may have a plating layer. For example, the heating workpiece may be a plated steel sheet. Examples of the plating layer include plating layers of aluminum alloy, aluminum-based alloy, zinc alloy, or zinc-based alloy.

[0098] In the above example, the heating workpiece has a constant thickness throughout. In contrast, the heating workpiece may be a stepped plate with a different thickness in part. The stepped plate may be, for example, a tailored blank material in which the ends of steel sheets with different plate thicknesses are butted and joined.

[0099] (Other Modifications) The present invention is not limited to the above-described embodiments. For example, the positions of the first heating workpiece W1 and the second heating workpiece W2 in the above-described embodiments may be interchanged with each other. For example, in the example of FIG. 7, the first heating workpiece W1 is disposed on top of the second heating workpiece W2, but conversely, the second heating workpiece W2 may be disposed on top of the first heating workpiece W1. Similarly, in the examples of FIGS. 8 and 10, the vertical arrangements of the first heating workpiece W1 and the second heating workpiece W2 may be interchanged. Also, in the above example, the facing direction of the two heating workpieces W1 and W2 is the vertical direction, but the facing direction may be inclined with respect to the vertical direction. In the above examples (except for the example of FIG. 7), the first heating workpiece W1 may be referred to as the second heating workpiece W2, and the second heating workpiece W2 may be referred to as the first heating workpiece W1. Also, in the above example, the entire end region of the first heating workpiece is bent toward the second heating workpiece, but a part of the end region may be parallel to the second heating workpiece. Even in this case, the effect of efficiently alleviating the temperature drop of the heating workpiece can be obtained. For example, a portion including the tip of the workpiece in the end region of the first heating workpiece may be parallel to the opposing portion of the second heating workpiece.

[0100] The conveying device is not limited to the above example. For example, the third arm 73 and the fourth arm 74 may be omitted. Also, in the above example, the lateral direction in which the pair of first arms 71 are arranged and the lateral direction in which the pair of second arms 72 are arranged are both the same in the x direction. As a modification of this, for example, a configuration may be adopted in which the pair of first arms 71 are arranged in the x direction and the pair of second arms 72 are arranged in the y direction perpendicular to the x direction. In the above example, the second arm 72 is longer than the first arm 71, but the first arm 71 may be longer than the second arm 72. Similarly, the third arm 73 may be longer than the fourth arm 74.

[0101] In the above-described embodiment, a plurality of pairs of the first arms 71 and a plurality of pairs of the second arms 72 are provided. In contrast, one pair of the first arms 71 and one pair of the second arms 72 may be provided.

[0102] The base frame 48 may be stretchable in the lateral direction (at least one of the x-direction and the y-direction).

[0103] In the above example, the conveying device 46 and the tray 1 convey the first heating workpiece W1 and the second heating workpiece W2 in a state where the facing direction of the first heating workpiece W1 and the second heating workpiece W2 coincides with the vertical direction. At least one of the conveying device 46 or the tray 1 may convey them in a state where the facing direction of the first heating workpiece W1 and the second heating workpiece W2 is inclined with respect to the vertical direction. Note that three or more heating workpieces may be conveyed simultaneously by the conveying device 46 or the tray 1. That is, a form in which three or more heating workpieces overlap in one direction and two of them are conveyed in a facing state is also included in the embodiments of the present invention.

[0104] (Experimental Example 1) The steel plate was heated, and the temperature change after the heating was measured under different conditions. Specifically, the following experiment was conducted. A thermocouple was attached to the plate surface of a steel plate with a thickness of 0.8 mm to measure the temperature. The steel plate was heated to 950 °C in a heating furnace, and the temperature drop was measured while being conveyed after being taken out of the heating furnace. The conditions of the examples and Comparative Examples 1 and 2 were as follows. Fig. 18(a) shows the arrangement of the steel plates in the example. Fig. 18(b) shows the arrangement of the steel plates in Comparative Example 1.

[0105] (Example) Two steel plates were stacked vertically (in the vertical direction), and 20 mm was bent inward at an angle of 30° from the ends of two opposite sides of each steel plate to form inclined portions. The vertical distance between the ends of the two steel plates was 10 mm. (Comparative Example 1) Two flat steel plates were stacked vertically (in the vertical direction) at a distance of 30 mm and heated and conveyed. (Comparative Example 2) One flat steel plate was heated and conveyed alone.

[0106] Figs. 19 and 20 are graphs of the average temperature drop rate as the measurement results. Fig. 19 shows the measurement results of the upper steel plate, and Fig. 20 shows the measurement results of the lower steel plate. From the measured temperature drop curve, the average temperature drop rate during about 8 seconds from when it was taken out of the furnace until the robot conveying was completed was derived.

[0107] In the measurement results, compared with Comparative Example 2 under the condition of a single flat plate, in Comparative Example 1 and the Example where steel plates were stacked in two upper and lower layers, the temperature drop rate decreased in both cases. That is, by transporting the steel plates in a state where they are stacked in two upper and lower layers and facing each other, a temperature drop mitigation effect was observed. Further, in the Example compared with Comparative Example 1, the temperature drop rate in the end region further decreased, and the difference from the inner temperature measurement position decreased. That is, it was found that the temperature drop of the steel plate can be efficiently mitigated by transporting under the condition that the end region is bent inward and stacked in two upper and lower layers with respect to the condition of stacking two flat plates in two upper and lower layers.

[0108] 46 Conveyor 48 Base frame 71 First arm 71b First claw 72 Second arm 72b Second claw W1 First heating workpiece W2 Second heating workpiece

Claims

1. A heating step of simultaneously heating at least two plate-shaped workpieces by a heating device, A conveying step of conveying the two heated workpieces heated in the heating step to a press machine, A pressing step of processing the two heated workpieces conveyed to the press machine in the conveying step by the press machine, and comprising: In the conveying step, The two heated workpieces are held in a state of facing each other, In at least a part of the end of the first heated workpiece among the two heated workpieces, an end region including the end of the first heated workpiece has a shape bent toward the second heated workpiece, and the distance in the facing direction of the two heated workpieces between the end of the first heated workpiece and the second heated workpiece is smaller than the maximum interval in the facing direction of the two heated workpieces. A method for manufacturing a press-formed product.

2. A method for manufacturing a press-formed product according to Claim 1, In the conveying step, at both ends of the first heated workpiece in at least one direction perpendicular to the facing direction, an end region including the end of the first heated workpiece has a shape bent toward the second heated workpiece, and the distance in the facing direction between the end of the first heated workpiece and the second heated workpiece is smaller than the maximum interval. A method for manufacturing a press-formed product.

3. A method for manufacturing a press-formed product according to Claim 1 or 2, In the conveying step, in at least a part of the end of the second heated workpiece, an end region including the end of the second heated workpiece has a shape bent toward the first heated workpiece. A method for manufacturing a press-formed product.

4. A method for manufacturing a press-formed product according to any one of Claims 1 to 3, In the conveying step, the end region of the first heated workpiece including the end of the first heated workpiece, the distance of which from the second heated workpiece is smaller than the maximum interval, includes an inclined portion inclined toward the second heated workpiece side with respect to a virtual plane perpendicular to the facing direction. A method for manufacturing a press-formed product.

5. A method for manufacturing a press-formed product according to Claim 4, In the conveying step, the angle between the inclined portion of the end region of the first heated workpiece and the portion including the end of the second heated workpiece closest to the inclined portion is 20° or more. A method for manufacturing a press-formed product.

6. A method for manufacturing a press-formed product according to Claim 4 or 5, In the transfer process, an end region including the end of the second heating workpiece facing the inclined portion of the end region of the first heating workpiece is inclined toward the first heating workpiece side with respect to a virtual plane perpendicular to the facing direction, and includes an inclined portion. A method for manufacturing a press-formed product.

7. A method for manufacturing a press-formed product according to any one of claims 1 to 6, In the transfer process, the distance in the facing direction between the end of the first heating workpiece that is smaller than the maximum distance and the second heating workpiece is 30 mm or less. A method for manufacturing a press-formed product.

8. A method for manufacturing a press-formed product according to any one of claims 1 to 7, In the transfer process, the two heating workpieces are transferred by a transfer device, The transfer process includes driving a pair of first arms rotatably attached to a base frame provided in the transfer device, and supporting and lifting the lower surfaces of both ends of the first heating workpiece with the claws of the pair of first arms; driving a pair of second arms rotatably attached to the base frame provided in the transfer device, and supporting and lifting the lower surfaces of both ends of the second heating workpiece with the claws of the pair of second arms; transferring the first heating workpiece supported by the lower surfaces of both ends with the claws of the pair of first arms of the transfer device and the second heating workpiece supported by the lower surfaces of both ends with the claws of the pair of second arms in a state of facing each other; driving the pair of first arms to lower the first heating workpiece supported by the pair of first arms to the press position of the press; driving the pair of second arms to lower the second heating workpiece supported by the pair of second arms to the press position of the press. A method for manufacturing a press-formed product.

9. A method for manufacturing a press-formed product according to any one of claims 1 to 8, In the transfer process, One of the first heating workpiece and the second heating workpiece is placed on at least three first support columns extending upward from a tray body having a hollow portion penetrating vertically when viewed from above, and the other heating workpiece of the first heating workpiece and the second heating workpiece is placed on at least three second support columns extending upward from the tray body, and above the one heating workpiece, in a state of being vertically overlapped with the one heating workpiece, a method for manufacturing a press-molded product, which is conveyed together with the tray body.

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