JP7712554B2 - Manufacturing method of press-molded products - Google Patents

Description

The present invention relates to a method for manufacturing press-molded products.

Conventionally, a technique has been used in which a material heated to a specified temperature is pressed with a press. For example, in hot pressing, the material, a steel plate for hot pressing, is heated to the austenite region (approximately 900°C or higher) and hot press-formed. This allows for quenching treatment along with forming, resulting in a press-formed product with a strength of, for example, 1500 MPa or higher. In general hot pressing, quenching is performed by rapidly cooling the material through contact heat transfer with a die during press forming. For this reason, in order to obtain a sufficient quenching effect, it is necessary to ensure that the temperature of the material at the start of press forming, which roughly corresponds to the quenching start temperature, is equal to or higher than a specified temperature. In this case, the specified temperature at the start of press forming is, for example, 700°C or higher, depending on the material.

Japanese Patent No. 5910305 and Japanese Patent No. 5910306 disclose a hot press forming method having a process of heating multiple overlapping conductive plate-shaped workpieces by attaching electrodes to the overlapping conductive plate-shaped workpieces and passing an electric current through the workpieces. The heated plate-shaped workpieces are placed at a predetermined press position different from the electric current passing position. The plate-shaped workpieces placed at the press position are each press-formed. By simultaneously heating multiple plate-shaped workpieces by passing an electric current through the workpieces, productivity is improved.

In the hot press processing method disclosed in JP 2019-177394 A, the first and second workpieces are heated without overlapping each other, and are carried in between the upper and lower dies, with the second workpiece placed on top of the first workpiece, and the upper die is lowered to press them. Before and after the pressing process, a mold tool is lowered independently of the upper die, and the first and second workpieces are plastically deformed. This causes the overlapping portions of the first and second workpieces to engage with each other and not shift. Also disclosed is a carrying device equipped with an arm for carrying the first workpiece and a holder for carrying the second workpiece.

In the above-mentioned conventional technology, heat dissipates during transport of the workpiece, causing the temperature of the workpiece to drop. As a result, the required temperature of the workpiece cannot be maintained when the workpiece is transported into the die of the press machine, and there is a risk that the press-molded product will not be sufficiently hardened.

Patent Publication No. 5814669 discloses a hot press transport device that holds and transports a heated panel-shaped transported object between each process of a production line where hot pressing is performed. The hot press transport device transports the heated transported object while covering it with a heat-retaining cover. This keeps the transported object at the temperature required for hardening during transport.

The hot press forming apparatus disclosed in Patent Publication No. 4673656 has a primary heating means using induction heating or electrical heating, and a secondary heating means using radiation heat transfer, as a heating device for the metal plate, which is the workpiece. The secondary heating means using radiation heat transfer is disposed in the transport device from the primary heating means to the hot press forming die. The secondary heating using radiation heat transfer allows the metal plate to be heated uniformly, and temperature deviation in the metal plate can be reduced.

Patent No. 5910305 Patent No. 5910306 JP 2019-177394 A Patent No. 5814669 Patent No. 4673656

The inventors realized that when the material for hot pressing is made thinner, the temperature drop during transportation of the material to the press machine after heating can affect the quality of the press-molded product. Therefore, they investigated a method for suppressing the temperature drop of the material during transportation. In their investigation, they found that it may be difficult to sufficiently suppress the temperature drop by simply covering the material with a heat-retaining cover during transportation, as in the above-mentioned conventional technology. It is also possible to provide a secondary heating means for heating the material during transportation. In this case, however, it is necessary to add equipment including a heat source for the secondary heating means to the transportation route. This may lead to an increase in the size of the equipment and an increase in equipment costs and operating costs.

Therefore, this application discloses a method for manufacturing a press-molded product that can efficiently mitigate the temperature drop of the heated workpiece during the time it takes to transport the heated workpiece to the press molding position.

The manufacturing method of the press-molded product in the embodiment of the present invention includes a heating process in which at least two plate-shaped workpieces are heated simultaneously by a heating device, a transport process in which the two heated workpieces heated in the heating process are transported to a press machine, and a press process in which the two heated workpieces transported to the press machine in the transport process are processed by the press machine. In the transport process, the two heated workpieces are held in a state facing each other. In at least a part of the end of the first heated workpiece of the two heated workpieces, the end region including the end of the first heated workpiece has a shape curved toward the second heated workpiece, and the distance between the end of the first heated workpiece and the second heated workpiece in the facing direction of the two heated workpieces is smaller than the maximum distance between the two heated workpieces in the facing direction.

According to the present disclosure, it is possible to efficiently mitigate the temperature drop of the heated workpiece during the transport time from when the material is heated in press molding until the start of press molding.

1 is a diagram showing an outline of a press production line according to an embodiment of the present invention; FIG. 2 is a diagram showing an example of a workpiece to be heated during transportation shown in FIG. 1 . FIG. 3 is a diagram showing radiant heat of the heating workpiece in the state shown in FIG. 2 . FIG. 13 is a diagram showing radiant heat when flat heating workpieces are stacked vertically. 13 is a perspective view showing an example in which inclined portions are provided at both ends in one direction perpendicular to the opposing direction of the first heated workpiece W1. FIG. 13 is a perspective view showing an example in which inclined portions are provided at both ends in two directions within a virtual plane perpendicular to the opposing direction of the first heated workpiece W1. FIG. 13A and 13B are diagrams showing modified examples of two heating workpieces in a conveying process. 13A and 13B are diagrams showing modified examples of two heating workpieces in a conveying process. 13A and 13B are diagrams showing modified examples of two heating workpieces in a conveying process. 13A and 13B are diagrams showing modified examples of two heating workpieces in a conveying process. 13A and 13B are diagrams showing modified examples of two heating workpieces in a conveying process. FIG. 2 is a side view showing a configuration example of the conveying device of FIG. 1 . 13 is a side view showing a state in which the second arm of the transport device of FIG. 12 is open. FIG. 1. FIG. 4 is a side view showing the configuration example of the conveying device of FIG. 1 as viewed from another direction. FIG. 13 is a diagram showing a modified example of the press production line according to the embodiment. FIG. 16 is a top view of the tray shown in FIG. 17 is a side view of the tray shown in FIG. 16 as viewed in the direction of arrow F. 1A shows the arrangement of steel plates in an example, and FIG. 1B shows the arrangement of steel plates in Comparative Example 1. FIG. 19 is a graph showing the average temperature decreasing rate of the upper steel plate as a result of the measurement. FIG. 20 is a graph showing the average temperature decreasing rate of the lower steel plate as a measurement result.

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 during the time it takes to transport the material to the press forming die after heating. The heating temperature of the material is determined by metallurgical conditions. The transport time to the die after heating is determined by the equipment configuration and specifications. The amount of temperature drop during the transport depends on the heat capacity of the material. For example, in the case of steel plates, heat is mainly lost by heat transfer to the atmosphere from the front and back sides and by heat radiation (radiation). The inventors have found that the amount of temperature drop is largely dependent on the thickness of the material. That is, as mentioned above, as the thickness of the material becomes thinner, the amount of temperature drop increases even with the same transport time, and it may be difficult to ensure the forming start temperature required for hardening. As a result, it may not be possible to obtain the part strength required for press formed products.

The inventors have studied ways to suppress temperature drop during transportation without adding a heat source. As a result of their study, they came up with a configuration in which multiple plate-shaped materials (heated workpieces) that are heated at the same time are transported facing each other. With this configuration, the opposing heated workpieces can receive each other's radiant heat, thereby compensating for each other's heat. Furthermore, a heat retention effect can be obtained by retaining air that has been warmed by heat transfer from both heated workpieces in the space between the opposing heated workpieces. As a result, it is possible to mitigate temperature drop during transportation.

After further investigation, the inventors came up with a configuration in which the end region including the edge of at least one of the two heated workpieces being transported has a shape that is curved toward the other opposing heated workpiece. They found that this makes it possible to efficiently mitigate the temperature drop of the heated workpieces. The following embodiment is based on this finding.

A method for producing a press-molded 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 process of conveying the two heated workpieces heated in the heating process to a press machine;
and a pressing process in which the two heated workpieces transported to the press machine in the transporting process are processed by the press machine.
In the transport step,
The two heating workpieces are held facing each other,
In at least a portion of the end of a first heated work of the two heated works, an end region including the end of the first heated work has a curved shape toward the second heated work, and the distance between the end of the first heated work and the second heated work in the opposing direction of the two heated works is smaller than the maximum spacing between the two heated works in the opposing direction.

According to the above manufacturing method, during transportation, at least a portion of the end of the first heated workpiece, the end region including the end has a shape that bends 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 region of the first heated workpiece has a shape in which the distance to the second heated workpiece becomes closer as the end is approached. This reduces the amount of radiant heat radiated from the end regions of the two heated workpieces that does not reach the opposing surface and escapes, and makes it difficult for the warmed stagnant air in the space between the two heated workpieces to escape. Therefore, during the time when the heated heated workpiece is transported to the press molding position, the overall temperature drop including the end region of the heated workpiece can be efficiently mitigated.

When two heated workpieces are transported, the state in which they face each other is when the plate surface (surface other than the side surface (i.e., end surface)) of the first heated workpiece faces the plate surface (surface other than the side surface) of the second heated workpiece. If there is a portion where the plate surfaces of the two heated workpieces facing each other are parallel, the facing direction is the direction perpendicular to the parallel plate surfaces. If there is no parallel portion on the plate surfaces of the two heated workpieces, the facing direction is the normal direction to the plate surface at the center of gravity of the first heated workpiece. If there are multiple parallel portions on the plate surfaces of the two heated workpieces, the facing direction is the direction perpendicular to the plate surface of the part with the largest area of the parallel portions.

When viewed from the opposing direction of the two heated workpieces, at least a portion of the first heated workpiece overlaps with the second heated workpiece. From the viewpoint of mitigating temperature drop, it is preferable that at least 70%, and preferably at least 80%, of both the first heated workpiece and the second heated workpiece overlap with the opposing other heated workpiece when viewed from the opposing direction.

In the first heated workpiece and the second heated workpiece, the end region is a region that includes the ends of the workpiece and the vicinity of the ends. The end region may be within a certain distance from the end of the workpiece. For example, the end region may be a portion that is 20% of the workpiece dimension from the end of the workpiece in a direction perpendicular to the facing direction.

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

In the conveying process, the first heated work may have an end region including the end of the first heated work that has a curved shape toward the second heated work at both ends in at least one direction perpendicular to the facing direction, and the distance between the end of the first heated work and the second heated work in the facing direction may be smaller than the maximum distance. This makes it possible to more efficiently mitigate the temperature drop of the heated work. Note that the distance between the second heated work and the first heated work in the facing direction may be smaller than the maximum distance only at one end of the both ends of the first heated work in the direction perpendicular to the facing direction. In this case, too, the effect of improving the efficiency of mitigating the temperature drop can be obtained.

For example, the distance between the first heated workpiece and the second heated workpiece may be smaller than the maximum distance between the two heated workpieces in the opposing direction in both the end region of one end and the end region of the other end of the first heated workpiece in at least one direction perpendicular to the opposing direction. In this case, there may be a portion between the one end and the other end where the distance between the two heated workpieces in the opposing direction is maximum.

In the conveying process, at least a portion of the end of the second heated workpiece, an end region including the end of the second heated workpiece, may have a shape that is curved toward the first heated workpiece. This makes it possible to more efficiently mitigate the temperature drop of the heated workpiece.

In the transport process, the end region of the first heated work, including the end of the first heated work where the distance from the second heated work is smaller than the maximum distance, may include an inclined portion inclined toward the second heated work with respect to a virtual plane perpendicular to the facing direction. This makes it possible to efficiently reduce the amount of radiant heat radiated from the inclined portion that does not reach the second heated work and escapes.

In the conveying process, it is preferable that 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. This makes it possible to more effectively mitigate the temperature drop of the heated workpiece. From the same viewpoint, the above angle is more preferably 40° or more, and even more preferably 60° or more. The end of the second heated workpiece closest to the inclined portion of the first heated workpiece is the end of the second heated workpiece at the position where the distance from the inclined portion of the first heated workpiece is the smallest. When the plate surface of the inclined portion of the first heated workpiece and the plate surface of the portion including the end of the second heated workpiece closest to the inclined portion are both flat, the angle between these planes or a virtual plane extending from them is the angle between the inclined portion of the first heated workpiece and the portion of the second heated workpiece. When the portion of the second heated workpiece includes an inclined portion inclined toward the first heated 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 heated workpiece or a virtual plane extending from it. When the plate surface of the inclined portion of the first heated work is curved, the above angle is determined based on a virtual plane that is tangent to the plate surface at the position closest to the end of the first heated work on the plate surface of the inclined portion. When the plate surface of the portion including the end of the second heated work closest to the inclined portion of the first heated work includes a curved surface, the above angle is determined based on a virtual plane that is tangent to the plate surface at the position closest to the end of the second heated work on the curved surface. In addition, in the inclined portion of the first heated work, if the plate surface on the inner side in the facing direction, i.e., the plate surface facing the second heated work, and the plate surface on the back side outside the facing direction, i.e., the plate surface opposite the second heated work, are not parallel, the above angle is determined based on the plate surface on the inner side in the facing direction. In the second heated work, in the portion including the end closest to the inclined portion of the first heated work, if the plate surface on the inner side in the facing direction (the plate surface facing the first heated work) and the plate surface on the outer side in the facing direction (the plate surface opposite the first heated work) are not parallel, the above angle is determined based on the plate surface on the inner side in the facing direction.

In the transport process, an end region including an end of the second heated workpiece facing the inclined portion of the end region of the first heated workpiece may include an inclined portion that is inclined toward the first heated workpiece with respect to a virtual plane perpendicular to the facing direction. This makes it possible to more efficiently reduce the amount of radiant heat radiated from the inclined portion of the second heated workpiece that does not reach the first heated workpiece and escapes.

In the conveying process, the distance in the facing direction between the end of the first heated workpiece and the second heated workpiece, which is smaller than the maximum distance, is preferably 30 mm or less. This makes it possible to more effectively mitigate the temperature drop of the heated workpiece. 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 heated workpiece and the second heated workpiece is not particularly limited, but from the viewpoint of mitigating the temperature drop, it is preferable that it is small. For example, the maximum distance is preferably 300 mm or less, more preferably 200 mm or less, and even more preferably 100 mm or less.

In the conveying step, the two heating workpieces may be conveyed by a conveying device. In this case, the conveying step includes:
A step of driving a pair of first arms rotatably attached to a base frame of the conveying device to support and lift the lower surfaces of both ends of the first heated workpiece with the claws of the pair of first arms;
Driving a pair of second arms rotatably attached to the base frame of the conveying device to support and lift the lower surfaces of both ends of the second heated workpiece with the claws of the pair of second arms;
A process of transporting the first heated workpiece, the lower surfaces of both ends of which are supported by the claws of the pair of first arms of the transport device, and the second heated workpiece, the lower surfaces of both ends of which are supported by the claws of the pair of second arms, in a state where they face each other;
A step of driving the pair of first arms to lower the first heated work supported by the pair of first arms to a press position (first press position) of the press machine;
The method may also include a step of driving the pair of second arms to lower the second heated workpiece supported by the pair of second arms into a press position (second press position) of the press machine.

This allows the first heated workpiece and the second heated workpiece to be transported in a state where they can efficiently receive heat radiation from each other, using a simple device configuration. Since both ends of the first heated workpiece and the second heated workpiece are supported by the first claw and the second claw, respectively, the distance between both ends of the two workpieces can be stably maintained. Therefore, the first and second heated workpieces can be transported simply and efficiently while suppressing temperature drop.

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.

In the transport process, one of the first heated workpiece and the second heated workpiece may be placed on a first group of at least three supports extending upward from a tray body having a hollow portion penetrating vertically when viewed from above, and the other of the first heated workpiece and the second heated workpiece may be placed on a second group of at least three supports extending upward from the tray body, and may be transported together with the tray body in a state where it is stacked vertically above the one heated workpiece.

In the above manufacturing method, after heating, the first heated workpiece and the second heated workpiece are transported from the heating device to a lifting position together with the tray. Therefore, after leaving the heating device, the first heated workpiece and the second heated workpiece are stacked vertically, for example, until they are lifted by a conveying device. In addition, one heated workpiece is placed on the first pillar group, and the other heated workpiece placed on the second pillar group is placed above it. The pillar group is formed by extending upward from the tray body. Therefore, for example, when the second heated workpiece and the first heated workpiece placed on the pillar group are lifted upward by a conveying device, the pillar group does not become an obstacle. The lifting operation can be performed simply and quickly. As a result, the first and second heated workpieces can be transported simply and efficiently while suppressing a temperature drop.

In the above manufacturing method, in the heating step, similar to the transport step, the one heating workpiece may be placed on a first group of at least three support columns extending upward from the tray body, and the other heating workpiece may be placed on a second group of at least three support columns extending upward from the tray body, and may be heated in a state where it is vertically stacked above the one heating workpiece. This allows the two heating workpieces to be transported while still in the heating step state on the tray body.

The following describes in detail an embodiment of the present invention with reference to the drawings. The same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated. The dimensional ratios between the components shown in each drawing do not necessarily represent the actual dimensional ratios.

(Embodiment 1)
Fig. 1 is a diagram showing an outline of a press production line 10 used in the production method of a press-molded product according to this embodiment. For the sake of explanation, Fig. 1 defines an xyz Cartesian coordinate system in which the vertical direction is the z direction. The vertical direction is the same as the direction of gravity. The press production 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.

In the heating device 14, two heated workpieces W1 and W2 are heated simultaneously. The heated workpieces W1 and W2 are transported to a lifting position RM on the transport table 16. At the lifting position RM, the heated workpieces W1 and W2 are lifted by the transport device 46 and transported to the pressing position of the press machine 20. The lifting position RM is preferably a position close to the outlet 14A of the heating device 14. The transport device 46 holds the heated workpieces W1 and W2 facing each other and transports them from the lifting position RM to the pressing position of the press machine 20. The press machine 20 press-forms the heated workpieces W1 and W2. As a result, the heated workpieces W1 and W2 are processed into press-formed products.

2 is a diagram showing an example of the heating workpieces W1 and W2 being transported by the transport device 46 shown in FIG. 1. As shown in FIG. 2, when transporting the heating workpieces W1 and W2, the two heating workpieces W1 and W2 are held in a vertically overlapping state. The two heating workpieces W1 and W2 are transported facing each other. In this example, the facing direction is the same as the vertical direction, as an example. In addition, at least a part of the end of the first heating workpiece W1 of the two heating workpieces W1 and W2, the end area including the end has a shape curved toward the second heating workpiece W2. Furthermore, at least a part of the end of the first heating workpiece W1, the distance D in the facing direction with the second heating workpiece W2 is smaller than the maximum distance Dmax in the facing direction of the two heating workpieces W1 and W2. That is, at least a part of the end of the first heating workpiece W1, the end area including the end includes a part that is not parallel to the part of the second heating workpiece W2 facing it. In the example shown in FIG. 2, in the area inside the end area of the plate surface of the first heated workpiece W1, the plate surface of the first heated workpiece and the plate surface of the opposing second heated workpiece are parallel.

In this way, by transporting the heating workpieces with the end regions of the two heating workpieces arranged close to each other, the amount of radiant heat radiated from the end regions of the heating workpieces W1 and W2 that does not reach the surface of the opposing heating workpiece can be reduced. 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 tilting the end region of one of the heating workpieces W1 and W2 inward, the radiant heat that reaches the other opposing heating workpiece can be increased. That is, as shown in FIG. 4, in a state where flat heating workpieces with no 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 direction of the arrows N1 and N2 in FIG. 4) does not reach the opposing heating workpiece and misses it. In the example of FIG. 3, the inclination of the end regions of the heating workpieces W1 and W2 can reduce the radiant heat that does not reach the heating workpiece and misses it. In addition, the warmed air trapped in the space between the two heating workpieces W1 and W2 is less likely to escape to the outside of the space. As a result, the temperature drop in the heating workpieces W1 and W2 during transport can be efficiently mitigated.

In the example of FIG. 2, the end region of the first heated workpiece W1 is bent toward the second heated workpiece W2, and the end region of the second heated workpiece W2 is bent toward the first heated workpiece W1. In this way, by transporting the two heated workpieces W1 and W2 in an inclined state so that their end regions approach each other, it becomes easier to achieve the effect of mitigating temperature drops.

Specifically, the end region of the first heated workpiece W1 includes an inclined portion W1k that inclines toward the second heated workpiece with respect to an imaginary plane perpendicular to the facing direction. Similarly, the end region of the second heated workpiece W2 also includes an inclined portion W2k that inclines toward the first heated workpiece with respect to an imaginary plane perpendicular to the facing direction. In this way, both the end region of the first heated workpiece W1 and the end region of the second heated workpiece W2, which face each other, are provided with inclined portions that approach each other as they approach the ends. This makes it possible to effectively suppress heat radiation and leakage of stagnant air.

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

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

From the viewpoint of enhancing the effect of mitigating temperature drop, it is preferable that the distance D between the end of the first heated workpiece W1 and the second heated workpiece W2 in the opposing direction is small. Although not limited thereto, for example, the distance D is preferably D≦30 mm, more preferably D≦20 mm, and even more preferably D≦10 mm.

2, at both ends in the x direction, which is a direction perpendicular to the facing direction of the first heated work W1, the distance D in the facing direction with the second heated work W2 is smaller than the maximum distance Dmax (D<Dmax). In this way, by reducing the distance between the two heated workpieces at both ends in the direction perpendicular to the facing direction, the stagnant air warmed between the first heated workpiece W1 and the second heated workpiece W2 is less likely to leak from the space between the heated workpieces. Also, in the example of FIG. 2, a sloping portion W1k is provided in the end region of each of both ends in the x direction of the first heated workpiece W1. By providing a sloping portion in the end region of both ends, the amount of heat radiated from the end region of both ends that does not reach the opposing heated workpiece and escapes is reduced. In the example of FIG. 2, a sloping portion W2k is also provided at both ends in the x direction of the second heated workpiece W2.

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

The inclined portions of the first heated workpiece W1 or the second heated workpiece W2 may be provided in the end regions at both ends in two mutually orthogonal directions, for example, the x and y directions, in a virtual plane perpendicular to the facing direction. This can further enhance the effect of mitigating temperature drops. In addition, two heated workpieces W1 and W2 may be arranged around the entire circumference of the end of the first heated workpiece W1 so that D<Dmax.

Figure 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 heated workpiece W1, and inclined portions are not provided in the end regions at both ends in the y direction. In the example of Figure 5, the end region at a portion of the end of the first heated workpiece W1 has a shape that is curved toward the second heated workpiece. Figure 6 is an example in which inclined portions are provided in the end regions at both ends in the x direction and y direction of the first heated workpiece W1. In the example of Figure 6, the end region at the entire end of the first heated workpiece W1 has a shape that is curved toward the second heated workpiece.

Figures 7 to 11 are diagrams showing modified examples of the arrangement of the first heated workpiece W1 and the second heated workpiece W2 in the conveying process. In the example of Figure 7, an inclined portion W1k is provided in the end region at both ends of the first heated workpiece W1 in one direction (for example, the x direction) perpendicular to the facing direction. The second heated workpiece W2 is a flat plate. In this case, the distance D in the facing direction between each of the two ends of the first heated workpiece W1 in the x direction and the second heated workpiece W2 is D < Dmax. In the example of Figure 7, the end of the first heated workpiece W1 is located at a position that overlaps with the end of the second heated workpiece W2 in the facing direction. In contrast, the end of the first heated workpiece W1 and the end of the second heated workpiece W2 do not have to overlap in the facing direction. For example, the end of the second heated workpiece W2 may be located inside the end of the first heated workpiece W1 when viewed from the facing direction. In such a case, the distance between the imaginary plane extending from the inner plate surface of the second heated workpiece W2 in the facing direction and the end of the first heated workpiece W1 is defined as the distance D between the end of the first heated workpiece W1 and the second heated workpiece W2 in the facing direction.

In the example of FIG. 8, an inclined portion W1k is provided in the end region of one of the ends in one direction (x direction as an example) perpendicular to the facing direction of the first heated workpiece W1. The end region of the second heated workpiece W2 facing the inclined portion W1k does not have an inclined portion and extends horizontally. An inclined portion W2k is provided in the end region of one of the ends in the direction perpendicular to the facing direction of the second heated workpiece W2 (x direction). The end of the first heated workpiece W1 facing the inclined portion W2k does not have an inclined portion and extends horizontally. In this case, too, the distance D in the facing direction between each of the ends in the x direction of the first heated workpiece W1 and the second heated workpiece W2 is D<Dmax. In this way, the heated workpieces W1 and W2 may be transported with an inclined portion arranged in one of the facing end regions of the two heated workpieces W1 and W2 and no inclined portion arranged in the other. Note that Figure 8 shows an example in which the end region of the first heated workpiece has a shape that is bent toward the second heated workpiece. In the examples of Figures 7 and 8, the preferred range of the angle θ1 between the inclined portion W1k of the first heated workpiece W1 and the portion including the end of the second heated workpiece W2 closest to the inclined portion W1k is the same as in the case of Figure 2 above.

In the example of FIG. 9, the inclined portion W1k of the first heated workpiece W1 and the inclined portion W2k of the second heated workpiece W2 both extend perpendicular to a virtual plane perpendicular to the opposing direction. The angle θ1 between the inclined portion W1k of the first heated workpiece W1 and the portion (inclined portion W2k) including the end of the second heated workpiece W2 closest to the inclined portion W1k is θ1 = 180°. In this way, the angle θ1 may be θ1 = 180°. However, in order to increase the angle θ1, it is necessary to increase the angle at which the workpiece is bent. In this case, the cost of processing the workpiece tends to be high. From the viewpoint of the workpiece processability, θ1 ≦ 180° is preferable, θ1 ≦ 160° is more preferable, and θ1 ≦ 140° is even more preferable. The inclined portions of the heated 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 that it is easy to press-form into the desired product shape.

In the example of FIG. 9, both ends of the first heated workpiece W1 in the x direction are in contact with the second heated workpiece W2. In this manner, the heated workpieces W1 and W2 may be transported with at least a portion of the end of the first heated workpiece W1 in contact with the second heated workpiece W2. This can further enhance the effect of mitigating the temperature drop.

In the example of FIG. 10, the first heated work W1 and the second heated work W2 are formed so that their central portions have a convex shape that protrudes in the same direction in the plate thickness direction, and the end regions include a shape that curves in a direction toward each other. In this way, the two intermediately formed workpieces can be transported facing each other as the first heated work W1 and the second heated work W2. In the example of FIG. 10, the first heated work W1 and the second heated work W2 are hat members. Parts of the flanges of the hat members are inclined portions W1k and W2k. As a modified example, the entire flange of the hat member may be inclined portions W1k and W2k. The hat 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 of the vertical wall opposite the top plate.

In the example of FIG. 11, the first heated work W1 and the second heated work W2 are curved to have a curvature (R) overall. Therefore, the inclined portions W1k and W2k in the end regions of the first heated work W1 and the second heated work W2 have a curvature (R). The plate surfaces of the inclined portions W1k and W2k are curved. In this way, the first heated work W1 may have a shape that is curved overall so that the central portion protrudes outward in the opposing direction. When the inclined portions of the end regions of the first heated work W1 or the second heated work W2 have a curvature, for example, as shown in FIG. 11, the angle between the imaginary plane that is in contact with the plate surface of the inclined portion of the first heated work W1 at a position closest to the end of the first heated work and the imaginary plane that is in contact with the plate surface of the second heated work W2 at a position closest to the end of the second heated work is the angle θ1. In the examples of FIG. 10 and FIG. 11, the preferred range of the angle θ1 is the same as that of FIG. 2 above.

The two heating workpieces W1 and W2 shown in Figures 2 and 5 to 11 above can be formed by bending a metal plate, except for the second heating workpiece W2 in Figure 7. In this embodiment, the first heating workpiece W1 and the second heating workpiece W2 that have been bent are heated in the heating device 14. In other words, the bending of the workpieces is performed before heating. The bending of the workpieces is performed, for example, by press forming.

(Example of a press production line)
An example of the device configuration of the press production line 10 shown in Fig. 1 will be described below. As an example, the press production line 10 is a hot press production line. In the example shown in Fig. 1, a conveying table 16 is arranged on a path from the heating device 14 to the press machine 20. An end of the conveying table 16 is connected to an outlet 14A of the heating device 14. An entrance 14B of the heating device 14 may be connected to, for example, another conveying table (not shown). A part of the conveying table 16 is a lifting position RM.

(heating device)
The heating device 14 is a device that heats the heating object (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, and may be, for example, a high-frequency induction heating device, a low-frequency induction heating device, or a current-carrying heating device that heats the heating object by directly applying current to the heating object. The heating device 14 may have a heating chamber. The heating device 14 may include a plurality of indoor rollers inside the heating chamber that are rotated by a driving mechanism (not shown). The heating object on the indoor rollers is transported by rotating the indoor rollers.

(Transport table)
The conveying table 16 includes a plurality of conveying rollers 26 that are rotated by a driving mechanism (not shown). Each conveying roller 26 rotates in synchronization with the indoor rollers, so that the conveying object (heated work) can be conveyed between the conveying table 16 and the heating chamber of the heating device 14. The plurality of conveying rollers 26 are arranged at intervals. The conveying table 16 is an example of a platform on which the heated work heated by the heating device is placed. The conveying table 16 is also an example of a conveying path that conveys the heated work from the heating device to the lifting position. The configuration of the conveying path is not limited to the conveying table 16 shown in FIG. 1. For example, the conveying path may be a belt conveyor or a rail. In the example shown in FIG. 1, the lifting position is on the conveying path, but the lifting position does not have to be on the conveying path. A platform that serves as the lifting position may be provided separately from the conveying path.

(Press machine)
The press machine 20 includes a lower die and an upper die for press-molding the object to be pressed. The lower die is, for example, a punch die, and the upper die is, for example, a die die. The upper die and the lower die may be provided with a coolant flow path. This allows the heat taken from the object to be pressed during pressing to be released through the coolant. Two heated workpieces can be arranged between the upper die and the lower die. The upper die and the lower die can be moved relatively. The press machine 20 presses the two heated workpieces by bringing the upper die and the lower die relatively close to each other with the two heated workpieces arranged between the upper die and the lower die. The operation 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 machine 20 are shaped to be able to manufacture multiple press-molded products at the same time. This is an example of a case where two pairs of dies are provided in one press machine. In this example, multiple workpieces are arranged between the lower die and the upper die of the press machine 20, and the multiple workpieces are pressed at the same time. Note that multiple press machines may be provided. For example, two press machines each having a pair of dies may be provided.

(manipulator)
The manipulator 44 uses the conveying device 46 to convey the object to be conveyed between the conveying table 16 and the press machine 20. The conveying device 46 lifts, holds, and places the workpiece to be conveyed. The manipulator 44 controls the position and attitude of the conveying device 46. The conveying device 46 may be an end effector of the manipulator 44. The manipulator 44 moves the conveying device 46 between a position above the conveying table 16 and a position between two pairs of dies (upper and lower dies) of the press machine 20. The manipulator 44 includes a base portion that can rotate around at least one axis, and an arm portion that extends from the base portion and has at least one joint. The conveying device 46 is rotatably attached to the tip of the arm portion. The moving device that moves the conveying device 46 is not limited to the manipulator. For example, the moving device may include a rail connecting the conveying table 16 and the press machine 20, and a suspension device that suspends the conveying device 46 on the rail so as to be movable up and down.

(controller)
The controller 22 controls the heating device 14, the conveying table 16, the press machine 20, and the manipulator 44. The controller 22 is configured as a control system including, for example, at least one computer. As an example, the controller 22 may include a control unit (for example, configured with a circuit or a processor) provided in each of the heating device 14, the conveying table 16, the manipulator 44, and the press machine 20, and controlling 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 manufacturing line 10. The operation of the arm of the conveying device 46 described later may be controlled by a part of the controller 22, for example, the control unit of the manipulator 44.

(Transportation device)
Fig. 12 is a side view showing a configuration example of the transport device 46 in Fig. 1 as viewed from the lateral direction (y direction). Fig. 13 is a diagram showing a state in which the second arm 72 of the transport device 46 in Fig. 12 is opened outward. Fig. 14 is a side view showing a configuration example of the transport device 46 in Fig. 1 as viewed from the lateral direction (x direction). Note that Figs. 12 to 14 show an example in which the first heated workpiece W1 is stacked on top of the second heated workpiece W2.

(Base frame)
12 and 13, the transport device 46 includes a base frame 48, a pair of first arms 71 and a pair of second arms 72 rotatably attached to the base frame 48. The shape of the base frame 48 is rectangular when viewed from above. In this example, the up-down direction (vertical direction) is defined as the z direction. The direction in a plane perpendicular to the up-down direction is defined as the lateral direction. Within the lateral direction, the long dimension direction of the base frame 48 is defined as the y direction, and the short dimension direction is defined as the x direction.

A joint 56 that is 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 an axis in the vertical direction relative to the manipulator 44.

(First Arm and Second Arm)
The pair of first arms 71 are disposed spaced apart in the horizontal direction (x direction). Each of the pair of first arms 71 has a first base 71a extending in the up-down direction from the base frame 48, and a first claw 71b bending and extending in the horizontal direction 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.

The pair of second arms 72 are spaced apart in the horizontal direction (x direction). Each of the pair of second arms 72 has a second base 72a extending in the vertical direction from the base frame 48, and a second claw 72b extending and bending in the horizontal direction 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.

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

In the example shown in Figures 12 and 13, the rotation shaft 60 of the first arm 71 and the rotation shaft 60 of the second arm 72 are coaxial. This allows the first arm 71 and the second arm 72 to be efficiently arranged on the base frame 48. Note that the rotation shaft 60 of the first arm 71 and the rotation shaft 60 of the second arm 72 do not have to be coaxial.

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

The actuator 82 is, for example, an air cylinder. The actuator 82 adjusts the extension amount 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 inserted in a long hole of a link 90 fixed to the second arm 72 so as to be movable and rotatable.

When each actuator 82 extends the operating shaft 82A, the corresponding second arm 72 extends downward, and the pair of second claws 72b of the pair of second arms 72 move closer to each other, entering a closed state, as shown in FIG. 12. When each actuator 82 retracts the operating shaft 82A, the pair of second claws 72b of the pair of second arms 72 move away from each other, entering an open state, as shown in FIG. 13.

The 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 to change the distance between the pair of first claws 71b in the lateral direction (x direction). The first drive unit that drives the first arms 71 can also be configured to include an actuator similar to the actuator 82 shown in Figures 12 and 13. The pair of first arms 71 are also controlled by the first drive unit to be in a closed state (see Figure 12) in which the pair of first claws 71b are close to each other, or in an open state in which the pair of first claws 71b are farther apart from each other than in the closed state. 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.

The pair of first claws 71b can support the undersides of both lateral ends of the first heated workpiece W1 when they are close to each other in the lateral direction, i.e., closed. The pair of second claws 72b can support the undersides of both lateral ends of the second heated workpiece W2 when they are close to each other in the lateral direction, i.e., closed.

(Third Arm and Fourth Arm)
12, 13, and 14, a pair of third arms 73 and a pair of fourth arms 74 are rotatably attached to a base frame 48. Although not shown, a third drive unit that drives the pair of third arms 73 and a fourth drive unit that drives the pair of fourth arms 74 are provided on the base frame 48. Note that the first to fourth drive units are not shown in FIG.

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 attached to the base frame 48 so as to be rotatable about a rotation axis 62 perpendicular to the rotation axis 60 of the first arm (x direction). 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 heated workpiece W1. In this example, the distance of the third claws 73b from the base frame 48 is different from the distance of the first claws 71b from the base frame 48. The distance of the third claws 73b from the base frame 48 can be determined depending on the shape of the workpiece to be supported.

The pair of fourth arms 74 are arranged side by side in a direction (y direction) perpendicular to the direction (x direction) in which the pair of second arms 72 are arranged (see FIG. 14). Each fourth arm 74 is attached to the base frame 48 so as to be rotatable about a rotation axis 62 perpendicular to the rotation axis 60 of the second arm (x direction). 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 pair of fourth claws 74b and the pair of second claws 72b support the lower surface of the second heated workpiece W2. In this example, the distance of the fourth claws 74b from the base frame 48 is different from the distance of the second claws 72b from the base frame 48. The distance of the fourth claws 74b from the base frame 48 can be determined depending on the shape of the workpiece to be supported.

(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. In addition, the third arm 73 and the fourth arm 74 are also 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.

(Example of transportation using trays)
The first heated workpiece W1 and the second heated workpiece W2 may be placed on a tray in a vertically overlapping state and transported to the lifting position RM. FIG. 15 is a diagram showing a modified example of the press production line 10 of FIG. 1. In the press production line 10 shown in FIG. 15, two heated workpieces W1 and W2 are heated and transported using a tray. The tray 1 is a tray on which the first heated workpiece W1 and the second heated workpiece W2 are placed in the heating device 14 and the transport 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 heated workpieces W1 and W2, and a second column group for placing the other heated workpiece. The first column group includes at least three columns configured to be able to support the lower surface of one heated workpiece. The second column group includes at least three columns configured to be able to support the other heated workpiece above one heated workpiece supported by the first column group. The first group of columns are arranged such that imaginary lines connecting the columns form at least one triangle when viewed from above. The second group of columns are arranged at a different position from the first group of columns when viewed from above, and are arranged such that imaginary lines connecting the columns form at least one triangle when viewed from above. All of the second group of columns are higher than the lowest column of the first group of columns.

In the heating device 14, the second heating workpiece W2 is placed on the first group of supports, and the first heating workpiece W1 is placed on the second group of supports and heated in a state where it is stacked above the second heating workpiece W2. The first heating workpiece W1 and the second heating workpiece W2 are transported from the heating device 14 to a lifting position on the transport table 16 by the transport device 46 while placed on the tray 1. As a result, the first and second heating workpieces W1 and W2 face each other during the period from when they are heated until when they are lifted by the transport device 46. This mitigates the temperature drop.

At the lifting position on the conveying table 16, the second heated work W2 placed on the first column group and the first heated work W1 placed on the second column group may be lifted upward at the same time while being supported by the second claw 72b of the second arm 72 of the conveying device 46 and the first claw 71b of the first arm 71, respectively, and conveyed to the respective pressing positions of the press machine 20 by the conveying device 46. At this time, the operation of driving the first arm 71 to place the pair of first claws 71b on the underside of the first heated work W1 and the operation of driving the second arm 72 to place the pair of second claws 72b on the underside of the second heated work W2 may be performed simultaneously or sequentially. By simultaneously lifting the first and second heated work W1 and W2 placed on the tray 1 by the conveying device 46, the conveying time can be shortened and the temperature drop can be further reduced. Also, the first heated workpiece W1 placed on the second pillar group may be lifted upward by the first claw 71b of the first arm 71 of the transport device 46, and then the second heated workpiece W2 placed on the first pillar group may be lifted by the second arm 72 of the transport device 46, and each may be transported to the pressing position of the press machine 20 by the transport device 46. When the transport device 46 simultaneously or sequentially lifts upward the second heated workpiece W2 placed on the first pillar group of the pillar group 3 and the first heated workpiece W1 placed on the second pillar group, the pillar group 3 does not become an obstacle.

The tray body 2 has a shape that extends vertically in the up-down direction, and may include a hollow portion that penetrates vertically. This allows heat from below the tray body 2 to be easily transferred to the first heated workpiece W1 and the second heated workpiece W2 during the heating process. The first and second support groups may be located between the hollow portions of the tray body 2 when viewed from above. This allows heat from below the tray body 2 to be easily transferred through the hollow portions around the first and second support groups to the second heated workpiece W2 placed on the first support group and the first heated workpiece W1 placed on the second support group.

(Tray)
FIG. 16 is a top view of the tray 1. FIG. 17 is a side view of the tray 1 shown in FIG. 16 as viewed from the direction of the arrow F. In the example shown in FIG. 16, the tray body 2 has a shape that spreads 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 larger than the area of the components of the tray body 2. The tray 1 has a plurality of supports 3 (3a, 3b) extending upward from the tray body 2. The plurality of supports 3 include a first support group 3a on which the second heating workpiece W2 can be placed, and a second support group 3b on which the first heating workpiece W1 can be placed above the second heating workpiece W2. 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.

(Tray body)
In the example shown in FIG. 16, the tray body 2 has a frame 2c and a bar member 2f that is bridged 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 parallel to each other with a space between them in the horizontal direction. The pair of horizontal frames 2a are arranged parallel to each other with a space between them in the vertical direction, between the pair of vertical frames 2b. The pair of vertical frames 2b and horizontal frames 2a form a rectangular frame 2c when viewed from above. The bar member 2f includes a vertical bar member 2d and a horizontal bar member 2e. The vertical bar member 2d is bridged between the pair of horizontal frames 2a. The horizontal bar member 2e is bridged between the pair of vertical frames 2b. The bar members 2f are arranged in a lattice pattern inside the frame 2c.

The bar member 2f (at least one of the vertical bar member 2d and the horizontal bar member 2e) may be configured so that its position in the frame 2c can be adjusted. For example, the frame 2c may be provided with a plurality of positioning holes or locking pieces. In this case, the bar member 2f is fixed to the holes or locking pieces of the frame 2c using fasteners or the like as necessary. By changing the position of the holes or locking pieces that fix the bar member 2f, the position of the bar member 2f in the frame 2c can be adjusted.

The components of the tray body 2 (in the example of FIG. 16, the frame 2c and the rod member 2f) may be pipe material or solid material. The components of the tray body 2 may be angle material with an L-shaped cross section or channel material with a U-shaped cross section. The material of the components of the tray body 2 is not particularly limited, but is formed of a heat-resistant material, such as heat-resistant steel or ceramics. The maximum operating temperature of the components is preferably 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 heat-resistant steel (heat-resistant alloy steel) that can be used as components include SCH22 (0.4C-25Cr-20Ni) and SCH24 (0.4C-25Cr-35Ni-Mo, Si). If the components of the tray body 2 are formed of heat-resistant alloy steel, processing and manufacturing are easier. In addition, the materials that can be used as components of the tray body 2 can also be used as materials for the support posts 3.

(post)
The first pillar group 3a includes at least three pillars whose virtual lines connecting the pillars form a triangle when viewed from above. The second pillar group 3b includes at least three pillars whose virtual lines connecting the pillars form a triangle when viewed from above. All of the second pillar group 3b are arranged at positions different from those of the first pillar group 3a when viewed from above. All of the second pillar group 3b are higher than the lowest pillar of the first pillar group 3a. This makes it possible for the first pillar group 3a and the second pillar group 3b to support the first heated workpiece W1 and the second heated workpiece W2 in a vertically stacked state.

The second support group 3b is arranged in an area where the other heated workpiece is placed when viewed from above, but does not overlap with the area where one heated workpiece is placed. The second support group 3b is also configured so that it does not overlap with the area where one heated workpiece is placed when viewed from above. In other words, the second support group 3b is configured so that one heated workpiece does not get caught on the second support group 3b when it is lifted upward by the conveying device 46.

In the example shown in FIG. 16, one of the heating workpieces (the second heating workpiece W2 in this example) has a notch on its edge (end) when viewed from above. The second support group 3b is arranged in the area corresponding to the notch of the second heating workpiece W2. In this way, by arranging the second support group 3b in the area corresponding to the notch or hole of one of the heating workpieces, the second support group 3b can be arranged in an area that does not overlap with one of the heating workpieces when viewed from above. The configuration of the first support group, the second support group, and the heating workpiece is not limited to the example shown in FIG. 16. For example, the first heating workpiece W1 and the second heating workpiece W2 of the same shape may be arranged in a shifted position 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 group 3b is arranged in a position that is an area where the first heating workpiece W1 is arranged and does not overlap with the area where the second heating workpiece W2 is arranged. In this case, there is no need to provide notches or holes in the second heated workpiece W2.

Referring to FIG. 17, the height of each of the first support group 3a corresponds to the shape of one of the heated workpieces (the second heated workpiece W2 in this example), and the height of each of the second support group 3b corresponds to the shape of the other heated workpiece (the first heated workpiece W1 in this example).

[Specific examples of manufacturing processes for press-molded products]
A description will now be given of an example of a process for manufacturing a press-molded product using the above-mentioned press production line 10. As described above, the manufacturing process for the press-molded product in this embodiment includes a heating process for heating a workpiece, a transport process for transporting the heated workpiece, and a pressing process for pressing the heated workpiece.

(Heating process)
In the heating process, at least two plate-shaped workpieces W1 and W2 are heated simultaneously by the heating device 14. Here, the mode of simultaneously heating multiple workpieces may be one in which the heating of multiple workpieces ends simultaneously, and the heating does not necessarily start simultaneously. In addition to the case where the heating of multiple workpieces ends exactly simultaneously, the mode of simultaneously heating multiple workpieces also includes the case where the heating ends slightly differently. For example, even if there is a difference of about the time it takes to lift the heated workpiece with the conveying device 46, it can be considered to be almost simultaneous from the viewpoint of the temperature drop of the heated workpiece during conveyance. The heated workpiece that has been heated is taken out of the heating device 14 by the rotation of the roller 13 of the heating device 14 and the conveying roller 26 of the conveying table 16.

(Transportation process)
As an example, the transport process includes a process of transporting the first heated workpiece W1 and the second heated workpiece W2 from the heating device 14 to a lifting position, a process of lifting the first heated workpiece W1 by the transport device 46, a process of lifting the second heated workpiece W2 by the transport device 46, a process of transporting the first and second heated workpieces W1, W2, a process of lowering the first heated workpiece W1 to the press position, and a process of lowering the second heated workpiece W2 to the press position.

An example of a process in which the transport device 46 lifts the first heated workpiece W1 is as follows. A pair of first arms 71 rotatably attached to the base frame of the transport device 46 is driven, and the claws of the pair of first arms 71 support and lift the underside of both ends of the first heated workpiece W1. At this time, the pair of first arms 71 and the pair of second arms 72 are opened, and the transport device 46 is lowered to approach the first heated workpiece W1 on the transport roller 26 of the transport table 16. By rotating the pair of first arms 71 to a closed state, the first claws of the pair of first arms 71 are inserted below the underside of both ends of the first heated workpiece W1. In this state, the transport device 46 is raised, and the underside of both ends of the first heated workpiece W1 is supported and lifted by the first claws of the pair of first arms 71.

An example of the process in which the transport device 46 lifts the second heated workpiece W2 is as follows. The transport device 46 drives a pair of second arms 72 to lift the second heated workpiece W2 while supporting and holding the underside of the first heated workpiece W1 with a pair of first arms 71. The transport device 46 supports and lifts the undersides of both ends of the second heated workpiece W2 with the second claws of the pair of second arms 72, similar to the lifting operation of the first heated workpiece W1.

The conveying device 46 conveys the first heated workpiece W1, the underside of which is supported by the first claws of the pair of first arms 71, and the second heated workpiece W2, the underside of which is supported by the second claws of the pair of second arms 72, in a state in which they overlap each other in the vertical direction of the first heated workpiece W1, i.e., in a state in which they face each other. Then, the conveying device 46 moves, for example, to the pressing position of the second heated workpiece W2. With the pair of first arms 71 supporting and holding the underside of the first heated workpiece W1, the conveying device 46 drives the pair of second arms 72 to an open state, and lowers the second heated workpiece W2 to the pressing position of the press machine 20. Then, the conveying device 46 moves to the pressing position of the first heated workpiece W1, drives the pair of first arms 71 to an open state, and lowers the first heated workpiece W1 to the pressing position of the press machine 20.

[Heated workpiece material]
The material of the heating workpiece may be any metal that can be molded. Examples of the material of the heating workpiece include, but are not limited to, Fe-based carbon steel, stainless steel, Al-based, and Ti-based materials. The heating workpiece may also have a plating layer. For example, the heating workpiece may be a plated steel sheet. Examples of the plating layer include an aluminum alloy, an aluminum-based alloy, a zinc alloy, or a zinc-based alloy.

In the above example, the heating workpiece has a constant thickness throughout. In contrast, the heating workpiece may be a differential thickness plate with thicknesses that vary in parts. A differential thickness plate may be, for example, a tailored blank material in which the ends of steel plates of different thicknesses are butted together and joined.

(Other Modifications)
The present invention is not limited to the above embodiment. For example, the positions of the first heated work W1 and the second heated work W2 in the above embodiment may be interchanged. For example, in the example of FIG. 7, the first heated work W1 is arranged on the second heated work W2, but conversely, the second heated work W2 may be arranged on the first heated work W1. Similarly, in the examples of FIG. 8 and FIG. 10, the upper and lower arrangements of the first heated work W1 and the second heated work W2 may be interchanged. In the above example, the opposing direction of the two heated workpieces W1 and W2 is vertical, but the opposing direction may be inclined relative to the vertical direction. In the above example (excluding the example of FIG. 7), the first heated workpiece W1 may be referred to as the second heated workpiece W2, and the second heated workpiece W2 may be referred to as the first heated workpiece W1. In the above example, the entire end region of the first heated workpiece is curved toward the second heated workpiece, but a part of the end region may be parallel to the second heated workpiece. In this case, the effect of efficiently mitigating the temperature drop of the heated workpiece can be obtained. For example, a small portion of the end region of the first heated workpiece, including the tip of the workpiece, may be parallel to an opposing portion of the second heated workpiece.

The transport 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 horizontal direction in which the pair of first arms 71 are lined up and the horizontal direction in which the pair of second arms 72 are lined up are both the same in the x direction. As a variation of this, for example, the pair of first arms 71 may be lined up in the x direction, and the pair of second arms 72 may be lined up 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.

In the above embodiment, multiple pairs of first arms 71 and multiple pairs of second arms 72 are provided. Alternatively, one pair of first arms 71 and one pair of second arms 72 may be provided.

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

In the above example, the conveying device 46 and tray 1 convey the first heated workpiece W1 and the second heated workpiece W2 with the opposing direction of the first heated workpiece W1 and the second heated workpiece W2 coinciding with the vertical direction. At least one of the conveying device 46 or tray 1 may convey the first heated workpiece W1 and the second heated workpiece W2 with the opposing direction of the first heated workpiece W1 and the second heated workpiece W2 inclined with respect to the vertical direction. In addition, three or more heated workpieces may be conveyed simultaneously by the conveying device 46 or tray 1. In other words, the embodiment of the present invention also includes a form in which three or more heated workpieces are conveyed overlapping in one direction and two of them are opposed to each other.

(Experimental Example 1)
The steel plate was heated, and the temperature change after heating was measured under different conditions. Specifically, the following experiment was carried out. A thermocouple was attached to the 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 the steel plate was transported after being removed from the heating furnace. The conditions for the example and comparative examples 1 and 2 were as follows. Figure 18(a) shows the arrangement of the steel plate in the example. Figure 18(b) shows the arrangement of the steel plate in comparative example 1.

(Example) Two steel plates were stacked vertically, and 20 mm from the ends of two opposing sides of each steel plate were bent inward at an angle of 30° to form inclined portions. The distance between the top and bottom ends of the two steel plates was 10 mm.
(Comparative Example 1) Two flat steel plates were stacked vertically with a distance of 30 mm between them, and were heated and transported.
(Comparative Example 2) One flat steel plate was heated and transported alone.

Figures 19 and 20 are graphs showing the average temperature drop rate as a result of the measurements. Figure 19 shows the measurement results for the upper steel plate, and Figure 20 shows the measurement results for the lower steel plate. From the measured temperature drop curves, the average temperature drop rate for approximately 8 seconds from removal from the furnace to the end of robot transport was derived.

The measurement results showed that the temperature drop rate was slower in both Comparative Example 1 and the Example, where the steel plates were arranged in two layers, compared to Comparative Example 2, which used a single flat plate. That is, by transporting the steel plates in two layers, facing each other, the effect of mitigating temperature drop was observed. Furthermore, compared to Comparative Example 1, the temperature drop rate in the Example was further slowed, and the difference with the inner temperature measurement position was reduced. That is, it was found that the temperature drop in the steel plate can be efficiently mitigated by transporting the steel plates in two layers, with the end regions folded inward.

46 Conveying device 48 Base frame 71 First arm 71b First jaw 72 Second arm 72b Second jaw W1 First heated workpiece W2 Second heated workpiece

Claims (9)

A heating step of simultaneously heating at least two plate-shaped workpieces by a heating device;
A conveying process of conveying the two heated workpieces heated in the heating process to a press machine;
A pressing process in which the two heated workpieces transported to the press machine in the transport process are processed by the press machine,
In the transport step,
The two heating workpieces are held facing each other,
A method for manufacturing a press-molded product, wherein in at least a portion of the end of a first heated work of the two heated works, an end region including the end of the first heated work has a curved shape toward the second heated work, and the distance between the end of the first heated work and the second heated work in the opposing direction of the two heated works is smaller than the maximum distance between the two heated works in the opposing direction. A method for producing a press-molded product according to claim 1,
A method for manufacturing a press-molded product, wherein, in the conveying process, at both ends of the first heated work in at least one direction perpendicular to the facing direction, an end region including the end of the first heated work has a curved shape toward the second heated work, and the distance in the facing direction between the end of the first heated work and the second heated work is smaller than the maximum distance. A method for producing a press-molded product according to claim 1 or 2,
A method for manufacturing a press-molded product, wherein in the conveying process, in at least a portion of the end of the second heated work, an end region including the end of the second heated work has a shape curved toward the first heated work. A method for producing a press-molded product according to any one of claims 1 to 3,
A method for manufacturing a press-molded product, wherein in the conveying process, the end region of the first heated work, including the end of the first heated work whose distance from the second heated work is smaller than the maximum distance, includes an inclined portion that is inclined toward the second heated work with respect to a virtual plane perpendicular to the opposing direction. A method for producing a press-molded product according to claim 4,
A method for manufacturing a press-molded product, wherein, in the conveying process, the angle between the inclined portion of the end region of the first heated work and the portion including the end of the second heated work closest to the inclined portion is 20° or more. A method for producing a press-molded product according to claim 4 or 5,
A method for manufacturing a press-molded product, wherein in the conveying process, an end region including the end of the second heated work facing the inclined portion of the end region of the first heated work includes an inclined portion that is inclined toward the first heated work with respect to a virtual plane perpendicular to the facing direction. A method for producing a press-molded product according to any one of claims 1 to 6,
A method for manufacturing a press-molded product, wherein in the conveying process, the distance in the opposing direction between the end of the first heated workpiece and the second heated workpiece, which is smaller than the maximum gap, is 30 mm or less. A method for producing a press-molded product according to any one of claims 1 to 7,
In the conveying step, the two heating workpieces are conveyed by a conveying device,
The conveying step includes:
A step of driving a pair of first arms rotatably attached to a base frame of the conveying device to support and lift the lower surfaces of both ends of the first heated workpiece with the claws of the pair of first arms;
Driving a pair of second arms rotatably attached to the base frame of the conveying device to support and lift the lower surfaces of both ends of the second heated workpiece with the claws of the pair of second arms;
A process of transporting the first heated workpiece, the lower surfaces of both ends of which are supported by the claws of the pair of first arms of the transport device, and the second heated workpiece, the lower surfaces of both ends of which are supported 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 heated work supported by the pair of first arms to a pressing position of the press machine;
A method for manufacturing a press-molded product, comprising: a step of driving the pair of second arms to lower the second heated workpiece supported by the pair of second arms into a pressing position of the press machine. A method for producing a press-molded product according to any one of claims 1 to 8,
In the transport step,
A manufacturing method for a press-molded product, in which one of the first heated work and the second heated work is placed on a group of at least three first pillars extending upward from a tray body having a hollow portion that penetrates vertically when viewed from above, and the other of the first heated work and the second heated work is placed on a group of at least three second pillars extending upward from the tray body, and is transported together with the tray body in a state where it is vertically stacked on top of one of the heated works above the other heated work.