Stacking system and stacking method

Abstract

To shorten a cycle time relating to stacking.SOLUTION: A stacking system 10 stacks a plurality of workpieces 30 placed on acquisition places, which are separate from each other, on a predetermined arrangement place, and includes: a robot arm 20 on which a hand 40 for holding the workpiece 30 is mounted at a tip end; and a control device 50 which controls an operation of the robot arm 20. The hand 40 has a structure capable of holding all of the plurality of workpieces 30 simultaneously in a state that the workpieces are stacked in multiple stages. The control device 50 executes holding processing in which a tip end of the robot arm 20 is moved to the periphery of the acquisition place and each of the plurality of workpieces 30 is held by the hand 40 one by one, and arrangement processing in which the tip end of the robot arm 20 is moved to the periphery of the arrangement place after all of the plurality of workpieces 30 are held by the hand 40 by repeatedly executing the holding processing, and all of the plurality of workpieces 30 are placed on the arrangement place while maintaining a state that the workpieces are stacked in multiple stages.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a stacking system and a stacking method using a robot arm. [Background technology]

[0002] In a production line or the like, there is a process in which a plurality of flat workpieces, which are randomly placed at a distance from each other, are stacked in a predetermined location. Stacking refers to stacking in multiple layers vertically. Patent Document 1 discloses a stacking device for performing such stacking. The stacking device disclosed in Patent Document 1 has a complex structure that is fixed at the position where stacking is performed. Therefore, in the past, a system for stacking using a robot arm has been considered for the purpose of improving the degree of freedom of movement and simplifying the structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-081741 A Summary of the Invention [Problem to be solved by the invention]

[0004] Normally, when stacking is performed using a robot arm, the operation flow is as follows. First, the tip of the robot arm is moved to the vicinity of the acquisition location where the workpiece is placed, and the workpiece is grasped by a hand attached to the tip of the robot arm. Then, the tip of the robot arm is moved to the vicinity of the placement location, and the workpiece is temporarily placed at the placement location. By performing these grasping and temporary placement operations for all the workpieces, multiple workpieces are stacked at the placement location. In stacking according to such a normal operation flow, the workpieces are temporarily placed one by one at the placement location and then stacked, which increases the movement distance of the robot arm, and as a result, there is a risk of extending the cycle time related to stacking.

[0005] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a stacking system and a stacking method that can shorten the cycle time related to stacking. [Means for solving the problem]

[0006] The stacking system of the embodiment is a system that stacks a plurality of workpieces placed at acquisition locations separated from each other in a predetermined placement location using a robot arm. The stacking system includes the robot arm having a hand attached to its tip for gripping the workpiece, and a control device that controls the operation of the robot arm. The hand is structured to be able to grip all of the plurality of workpieces simultaneously in a state where the workpieces are stacked in multiple layers. The control device executes a gripping process in which the tip of the robot arm is moved to the vicinity of the acquisition location and each of the plurality of workpieces is gripped one by one by the hand, and an arrangement process in which the tip of the robot arm is moved to the vicinity of the arrangement location and all of the plurality of workpieces are placed in the arrangement location while maintaining the state where the workpieces are stacked in multiple layers. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of a stacking system according to an embodiment, showing a state in which a plurality of workpieces are located at different acquisition locations; [Diagram 2] FIG. 1 is a schematic diagram illustrating a configuration of a stacking system according to an embodiment, showing a state in which a plurality of works are stacked in a placement location. [Diagram 3] FIG. 1 is a diagram showing a first specific configuration example of a hand according to an embodiment; [Figure 4] FIG. 13 is a diagram showing a second specific configuration example of a hand according to an embodiment; [Diagram 5] FIG. 13 is a diagram showing a third specific configuration example of the hand according to an embodiment; [Figure 6]FIG. 11 is a diagram showing a fourth specific configuration example of a hand according to an embodiment; [Figure 7] FIG. 13 is a diagram showing a fourth specific configuration example of the hand according to the embodiment, illustrating a state in which the placement unit is tilted upward. [Figure 8] FIG. 13 is a diagram showing a fifth specific configuration example of the hand according to the embodiment, illustrating a state in which the hand is not gripping a workpiece. [Figure 9] FIG. 13 is a diagram showing a fifth specific configuration example of the hand according to the embodiment, illustrating a state in which one workpiece is being gripped; [Figure 10] FIG. 13 is a diagram showing an example of the contents of a first process executed by a control device according to an embodiment; [Figure 11] FIG. 1 is a diagram for explaining a flow of a series of operations when a control device according to an embodiment executes a first process; [Figure 12] FIG. 11 is a diagram showing an example of the content of a second process executed by the control device according to an embodiment; [Figure 13] FIG. 11 is a diagram for explaining a flow of a series of operations when a control device according to an embodiment executes a second process; [Figure 14] FIG. 11 is a diagram showing an example of the content of a third process executed by the control device according to an embodiment; [Figure 15] FIG. 11 is a diagram for explaining a flow of a series of operations when a control device according to an embodiment executes a third process; [Figure 16] FIG. 13 is a diagram for explaining the movement distance of the arm tip in stacking according to a comparative example; [Figure 17] FIG. 13 is a diagram for explaining a moving distance of an arm tip in stacking according to an embodiment; [Figure 18] FIG. 11 is a diagram for explaining an operation when gripping the second or subsequent workpieces in a case where a hand of a second configuration example according to an embodiment is adopted; [Figure 19] FIG. 1 is a diagram for explaining an operation when gripping a second or subsequent workpiece in a case where a hand of a first configuration example according to an embodiment is adopted; [Figure 20] FIG. 13 is a perspective view showing a configuration of a modified example of the hand according to the embodiment, in a state where the hand is not gripping a workpiece; [Figure 21]FIG. 13 is a perspective view showing a configuration of a modified example of the hand according to the embodiment, illustrating a state in which the hand is gripping a workpiece; [Figure 22] 1 is a diagram showing a state in which a plurality of stacked workpieces are slightly misaligned with respect to each other and a state in which the plurality of stacked workpieces are aligned according to an embodiment; FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, a stacking system according to an embodiment will be described with reference to the drawings. As shown in FIG. 1 and FIG. 2, the stacking system 10 is a system that stacks a plurality of workpieces 30a, 30b, and 30c using a robot arm 20. Specifically, the stacking system 10 is a system that stacks a plurality of workpieces 30a to 30c that are randomly placed as shown in FIG. 1, that is, a plurality of workpieces 30a to 30c that are placed at acquisition locations separated from each other, at a predetermined placement location as shown in FIG. 2. The acquisition location and the placement location are set at any location such as a platform or container having a flat surface. Stacking means stacking in multiple layers in a direction perpendicular to the plane of the placement location. In the following description, when there is no need to distinguish between the workpieces 30a to 30c, they will be collectively referred to as the workpieces 30.

[0009] In this embodiment, three workpieces 30a to 30c are stacked, but the number of workpieces 30 to be stacked is not limited to three, and may be two, four or more. However, the number of workpieces to be stacked is limited to the number that the robot arm 20 can hold. The robot arm 20 is configured as a horizontal articulated robot having, for example, a four-axis arm. The workpiece 30 is, for example, food, and has a so-called flat shape. Specifically, the workpiece 30 has a flat plate shape having two main surfaces 31 and 32 facing each other. In this specification, one of two mutually orthogonal directions along the main surfaces 31 and 32 of the workpiece 30 is defined as a left-right direction, and a direction perpendicular to the main surfaces 31 and 32 is defined as a top-bottom direction.

[0010] A hand 40 for gripping a workpiece 30 is attached to the tip of the robot arm 20. The hand 40 is structured so that it can simultaneously grip all of the workpieces 30 stacked in multiple stages. Although Fig. 1 and Fig. 2 show one configuration example of the hand 40 having such a structure, the structure of the hand 40 is not limited to this, and various structures can be adopted, including various structures described later.

[0011] The operation of the robot arm 20 including the hand 40 is controlled by a control device 50. The control device 50 controls the operation of the robot arm 20 by executing a computer program in a control means made up of a computer including a CPU, a ROM, a RAM, etc. (not shown). The control device 50 includes functional blocks such as a gripping processing unit 51 and a placement processing unit 52. Each of these functional blocks is realized by a CPU included in the control device 50 executing a computer program stored in a ROM or the like to perform processing corresponding to the computer program, that is, by software. Note that at least a part of each functional block may be realized by hardware.

[0012] The gripping processing unit 51 executes a gripping process in which the arm tip 21, which is the tip of the robot arm 20, is moved to the vicinity of the acquisition location, and each of the multiple workpieces 30 is gripped one by one by the hand 40. The placement processing unit 52 executes a placement process in which the gripping processing unit 51 repeatedly executes the gripping process to grip all of the multiple workpieces 30 with the hand 40, and then moves the arm tip 21 to the vicinity of the placement location, and places all of the multiple workpieces 30 at the placement location while maintaining them in a state of being stacked in multiple layers.

[0013] <Specific examples of hand configuration> As a specific configuration of the hand 40 attached to the arm tip 21 of the robot arm 20, the following five configuration examples can be adopted.

[0014] [1] First configuration example As shown in FIG. 3, the hand 40A of the first configuration example includes two claws 41A and 42A that move in parallel in the left-right direction to open and close. The tips of the two claws 41A and 42A are provided with placement sections 43A and 44A that extend in the left-right direction. The placement section 43A has a uniform thickness, which is the dimension in the up-down direction, from the base end, which is the left end in FIG. 3, to the tip end, which is the right end in FIG. 3. The placement section 44A has a uniform thickness from the base end, which is the right end in FIG. 3, to the tip end, which is the left end in FIG. 3. The thickness of the placement sections 43A and 44A is smaller than the thickness of the workpiece 30.

[0015] [2] Second configuration example As shown in FIG. 4, the hand 40B of the second configuration example includes two claws 41B and 42B that move in parallel in the left-right direction to open and close. The tips of the two claws 41B and 42B are provided with placement parts 43B and 44B that extend in the left-right direction. The placement part 43B has a shape in which the thickness gradually decreases from the base end, which is the left end in FIG. 4, to the tip end, which is the right end in FIG. 3, that is, a shape that slopes downward from the base end to the tip end. The placement part 44B has a shape in which the thickness gradually decreases from the base end, which is the right end in FIG. 4, to the tip end, which is the left end in FIG. 4, that is, a shape that slopes downward from the base end to the tip end. In addition, the thickness of the placement parts 43B and 44B at the base end is approximately the same as or larger than the thickness of the workpiece 30.

[0016] [3] Third configuration example As shown in FIG. 5, the hand 40C of the third configuration example includes two claws 41C and 42C that move in parallel in the left-right direction to open and close. The tips of the two claws 41C and 42C are provided with placement sections 43C and 44C that extend along the left-right direction. The placement section 43C has a uniform thickness, which is the dimension in the up-down direction, from the base end, which is the left end in FIG. 5, to the tip end, which is the right end in FIG. 5. The placement section 44C has a uniform thickness from the base end, which is the right end in FIG. 5, to the tip end, which is the left end in FIG. 5. The thickness of the placement sections 43C and 44C is approximately the same as or larger than the thickness of the workpiece 30.

[0017] [4] Fourth configuration example As shown in FIG. 6, the hand 40D of the fourth configuration example includes two claws 41D and 42D that move in parallel in the left-right direction to open and close. At the tips of the two claws 41D and 42D, placement sections 43D and 44D are provided that extend along the left-right direction. The placement section 43D has a uniform thickness, which is the dimension in the up-down direction, from the base end, which is the left end in FIG. 6, to the tip end, which is the right end in FIG. 6. The placement section 44D has a uniform thickness from the base end, which is the right end in FIG. 6, to the tip end, which is the left end in FIG. 6. The thickness of the placement sections 43D and 44D is smaller than the thickness of the workpiece 30.

[0018] As shown in Fig. 7, the placement portion 43D is configured so that its tip portion can rotate upward around its base end portion. Although not shown, the placement portion 44D is also configured so that its tip portion can rotate upward around its base end portion, similar to the placement portion 43D. In other words, the placement portions 43D and 44D are configured so that their tips can only tilt upward.

[0019] [5] Fifth configuration example As shown in FIG. 8 and FIG. 9, the hand 40E of the fifth configuration example includes one claw portion 41E. At the tip of the claw portion 41E, three placement portions 43E, 44E, and 45E extending in the left-right direction are provided so as to be stacked in the up-down direction. The number of placement portions is not limited to three, and may be any number equal to or greater than the number of works 30 to be stacked. The placement portions 43E to 45E are configured to be individually movable in the up-down direction. In addition, the placement portions 43E to 45E are configured to be individually or collectively movable toward the outside of the hand 40E in the left-right direction. In other words, the placement portions 43E to 45E are configured to be removable from the hand 40E.

[0020] <Specific examples of gripping and placement processing> The following contents can be adopted as specific contents of the gripping process and the placement process executed by the control device 50. In the following, examples of specific processing contents corresponding to each of the first to fifth configuration examples of the hand 40 will be described with reference to Figs. 10 to 15.

[0021] [1] Contents of the first process corresponding to the first to third configuration examples When the hand 40A of the first configuration example, the hand 40B of the second configuration example, or the hand 40C of the third configuration example is adopted as the hand 40, the control device 50 can execute a first process having contents as shown in Fig. 10. The first process is a process for realizing a method of adding a workpiece 30 to be grasped by the hand 40 by opening and closing the hand 40. In this case, steps S102, S103, S104, and S105 correspond to the grasping process, and steps S107, S108, and S109 correspond to the placement process.

[0022] In step S101, one of the three workpieces 30 that has not yet been gripped by the hand 40 is set as a target workpiece that is a workpiece to be gripped. In step S102, a process is executed to move the hand 40 to a position above the target workpiece, that is, to a position above the target workpiece. In step S103, a process is executed to open the two claws 41A, 42A, etc. in the left-right direction, that is, to open the hand 40. Steps S102 and S103 can be executed in reverse order or simultaneously.

[0023] In step S104, the hand 40 is moved downward, that is, the hand 40 is lowered toward the target workpiece. In step S105, the two claws 41A, 42A, etc. are closed in the left-right direction, that is, the hand 40 is closed to place the target workpiece on the placement parts 43A, 44A, etc. In step S106, it is determined whether or not all of the three workpieces 30 are gripped by the hand 40. Here, if all of the three workpieces 30 are not gripped by the hand 40, the result in step S106 is "NO" and the process returns to step S101. On the other hand, if all of the three workpieces 30 are gripped by the hand 40, the result in step S106 is "YES" and the process proceeds to step S107.

[0024] In step S107, a process is executed to move the hand 40 to a position above the placement location. In step S108, a process is executed to move the hand 40 downward, that is, to lower the hand 40 toward the placement location. In step S109, a process is executed to open the two claws 41A, 42A, etc. in the left-right direction, that is, to open the hand 40, thereby placing the target workpiece at the placement location. After execution of step S109, this process ends.

[0025] When the first process is performed by the control device 50, the workpieces 30 are stacked by a series of operations as shown in FIG. 11. Note that FIG. 11 illustrates an example in which the hand 40A of the first configuration example is used as the hand 40, but the workpieces 30 are stacked by a similar series of operations even when the hand 40B of the second configuration example or the hand 40C of the third configuration example is used as the hand 40. First, as shown in the first row of FIG. 11, an operation of gripping the first workpiece 30a is performed. The operations of gripping the workpiece 30 are, from the left side of FIG. 11, "(1) moving the hand 40A above the target workpiece" → "(2) opening the hand 40A" → "(3) lowering the hand 40A toward the target workpiece" → "(4) closing the hand 40A to place the target workpiece on the placement parts 43A and 44A."

[0026] Next, as shown in the second row of Fig. 11, an operation of gripping the second workpiece 30b is performed. After that, as shown in the third row of Fig. 11, an operation of gripping the third workpiece 30c is performed, and finally, an operation of placing the three workpieces 30 at the placement location is performed. Although not shown in the figure, the operation of placing the three workpieces 30 at the placement location is as follows: "Move hand 40A to a position above the placement location" -> "Descend hand 40A toward the placement location" -> "Open hand 40A". As a result, the three workpieces 30 are placed at the placement location in a stacked state.

[0027] [2] Details of the second process corresponding to the fourth configuration example When the hand 40D of the fourth configuration example is adopted as the hand 40, the control device 50 can execute the second process shown in Fig. 12. The second process is a process that realizes a method of adding a workpiece 30 to be gripped by the hand 40D by utilizing the structure in which the tips of the placement parts 43D and 44D are tilted only upward. The second process differs from the first process shown in Fig. 10 in that steps S103 and S105 are omitted. In this case, steps S102 and S104 correspond to the gripping process, and steps S107, S108, and S109 correspond to the placement process.

[0028] In the second process, step S104 is executed after step S102 is executed. In this case, when step S104 is executed, the tip of the hand 40D descends until it reaches the plane of the acquisition location, and the placement units 43D and 44D at the tip of the hand 40D tilt upward, so that the target workpiece enters inside the hand 40D. After that, the placement units 43D and 44D at the tip of the hand 40D return to their original state, so that the target workpiece is placed on the placement units 43D and 44D. In this case, step S104 corresponds to a process of placing the target workpiece on the placement units 43D and 44D by moving the hand 40D downward.

[0029] When the hand 40D of the fourth configuration example is employed as the hand 40 and the second process is executed by the control device 50, the workpieces 30 are stacked in layers by a series of operations as shown in Fig. 13. First, as shown in the first row of Fig. 13, an operation of gripping the first workpiece 30a is performed. The operations of gripping the workpiece 30 are, in order from the left side of Fig. 13, "(1) moving the hand 40D above the target workpiece" -> "(2) lowering the hand 40D toward the target workpiece to place the target workpiece inside the hand 40D" -> "(3) placing parts 43D, 44D return to their original states to place the target workpiece on placing parts 43D, 44D."

[0030] Next, as shown in the second row of Fig. 13, an operation of gripping the second workpiece 30b is performed. After that, as shown in the third row of Fig. 13, an operation of gripping the third workpiece 30c is performed, and finally, an operation of placing the three workpieces 30 at the placement location is performed. Although not shown in the figure, the operation of placing the workpieces 30 at the placement location is as follows: "Move the hand 40D to a position above the placement location" -> "Descend the hand 40D toward the placement location" -> "Open the hand 40D". As a result, the three workpieces 30 are placed at the placement location in a stacked state.

[0031] [3] Contents of the third process corresponding to the fifth configuration example When the hand 40E of the fifth configuration example is adopted as the hand 40, the control device 50 can execute a third process as shown in Fig. 14. The third process is a process for realizing a method of adding a workpiece 30 to be gripped by the hand 40E by placing the workpiece on the placement parts 43E-45E and raising the placement parts 43E-45E.

[0032] The third process differs from the first process shown in Fig. 10 in that step S103 is omitted, steps S201 and S202 are provided instead of step S105, and step S203 is provided instead of step S109. In this case, steps S102, S104, S201, and S202 correspond to the gripping process, and steps S107, S108, and S203 correspond to the placement process.

[0033] Step S201 is executed after step S104. In step S201, a process is executed to move the hand 40E in the right direction, which is the direction toward the target work, of the left and right directions, so that the placement unit 43E, etc. is placed under the target work, that is, the target work is placed on the placement unit 43E, etc. In this case, steps S104 and S201 correspond to a process of placing the target work on any of the placement units 43E to 45E by moving the hand 40E downward and in the left and right directions.

[0034] In the following step S202, a process is executed to move any one of the placement parts 43E-45E on which the target work is placed upward, that is, to raise any one of the placement parts 43E-45E on which the target work is placed. After execution of step S202, step S106 is executed. Step S203 is executed after step S108. In step S203, a process is executed to place the target work in the placement location, specifically, a process to tilt the hand 40E in the vertical direction, or a process to move the placement parts 43E-45E in the horizontal direction to remove the target work from the hand 40E. After execution of step S203, this process ends.

[0035] When the hand 40E of the fifth configuration example is employed as the hand 40 and the third process is executed by the control device 50, the workpieces 30 are stacked in layers by a series of operations as shown in Fig. 15. First, as shown in the first row of Fig. 15, an operation to grip the first workpiece 30a is performed. The operations to grip the workpiece 30 are, in order from the left side of Fig. 15, "(1) move the hand 40E above the target workpiece" → "(2) lower the hand 40E toward the target workpiece" → "(3) move the hand 40E rightward to place one of the placement units 43E to 45E under the target workpiece" → "raise one of the placement units 43E to 45E on which the target workpiece is placed."

[0036] Next, as shown in the second row of FIG. 15, an operation of gripping the second workpiece 30b is performed. After that, as shown in the third row of FIG. 15, an operation of gripping the third workpiece 30c is performed, and finally, an operation of placing the three workpieces 30 at the placement location is performed. Although some illustrations are omitted, the operation of placing the workpieces 30 at the placement location is as follows: "Move the hand 40E to a position above the placement location" -> "Descend the hand 40E toward the placement location" -> "(X) Tilt the hand 40E" or "(Y) Pull out the placement parts 43E-45E". As a result, the three workpieces 30 are placed at the placement location in a stacked state.

[0037] According to the present embodiment described above, the following effects can be obtained. The stacking system 10 of this embodiment is a system that stacks multiple workpieces 30 placed at acquisition locations separated from each other in a predetermined placement location using a robot arm 20. The stacking system 10 includes a robot arm 20 having a hand 40 attached to its tip for gripping the workpieces 30, and a control device 50 that controls the operation of the robot arm 20. The hand 40 is structured to be able to grip all of the multiple workpieces 30 simultaneously in a state where they are stacked in multiple layers. The control device 50 executes a gripping process in which the tip of the robot arm 20 is moved to the vicinity of the acquisition location and each of the multiple workpieces 30 is gripped one by one by the hand 40, and an arrangement process in which the tip of the robot arm 20 is moved to the vicinity of the arrangement location and all of the multiple workpieces 30 are placed in the arrangement location while maintaining the state where they are stacked in multiple layers.

[0038] In this way, the movement distance of the arm tip 21 of the robot arm 20 is kept short compared to stacking according to a normal operation flow in which the workpieces 30 are temporarily placed one by one, and therefore the cycle time related to stacking can be significantly shortened. The effects obtained by this embodiment will be described in detail below with reference to Figs. 16 and 17. Note that, hereinafter, stacking according to a normal operation flow in which the workpieces 30 are temporarily placed one by one may be referred to as stacking according to a comparative example. In Figs. 16 and 17, the initial position of the arm tip 21 of the robot arm 20 is indicated by a hollow circle, and the general movement trajectory of the arm tip 21 is indicated by an arrow.

[0039] In the stacking according to the comparative example, as shown in Fig. 16, the arm tip 21 of the robot arm 20 moves in the order of "initial position" → "acquisition location of the first workpiece 30a" → "placement location" → "acquisition location of the second workpiece 30b" → "placement location" → "acquisition location of the third workpiece 30c" → "placement location." In contrast, in the stacking according to the present embodiment, as shown in Fig. 17, the arm tip 21 of the robot arm 20 moves in the order of "initial position" → "acquisition location of the first workpiece 30a" → "acquisition location of the second workpiece 30b" → "acquisition location of the third workpiece 30c" → "placement location."

[0040] 16 and 17, according to the stacking of this embodiment, the movement distance of the arm tip 21 of the robot arm 20 is kept shorter than that of the stacking of the comparative example. Specifically, according to the stacking of this embodiment, the movement distance of the arm tip 21 is kept shorter than that of the stacking of the comparative example by a distance mainly corresponding to the movement distance for returning from the placement location to the acquisition location, and as a result, the cycle time can be shortened by the time required for such movement.

[0041] By adopting any one of the first to third configuration examples as the hand 40 and having the control device 50 execute the first process, the hand 40 only needs to be configured to be capable of performing opening and closing operations, so that the structure can be simple and a relatively inexpensive hand 40 can be adopted, resulting in cost reduction effects.

[0042] By adopting the fourth configuration example for the hand 40 and having the control device 50 execute the second process, opening and closing of the hand 40 is not required when grasping the workpiece 30, making it possible to further shorten the cycle time for stacking.

[0043] When the hand 40A of the first configuration example or the hand 40D of the fourth configuration example is used as the hand 40, there are the following advantages over when the hand 40B of the second configuration example or the hand 40C of the third configuration example is used as the hand 40. That is, as shown in Fig. 18, the thickness of the placement portions 43B and 44B of the hand 40B is approximately the same as or greater than the thickness of the workpiece 30. Although not shown in the drawings, the same is true of the hand 40C.

[0044] 19, the thickness of the placement portions 43A and 44A of the hand 40A is smaller than the thickness of the workpiece 30. Although not shown, the same is true for the hand 40D. In this manner, the thickness of the placement portions 43A and 44A of the hand 40A is smaller than the thickness of the placement portions 43B and 44B of the hand 40B.

[0045] With a hand 40B having relatively thick mounting portions 43B, 44B, when the hand 40B is opened to grasp a second or subsequent workpiece 30, as shown in FIG. 18, the lower main surface 32 of the lowermost workpiece 30b of the works 30 already being held is largely separated from the upper main surface 31 of the workpiece 30c to be grasped, causing the already held workpiece 30 to fall from a relatively high position and receive an impact.

[0046] In contrast, with the hand 40A having the placement portions 43A and 44A that are relatively thin, as shown in Fig. 19, when the hand 40A is opened to grasp the second or subsequent workpieces 30, the lower main surface 32 of the lowermost workpiece 30b among the already held workpieces 30 and the upper main surface 31 of the workpiece 30c to be grasped are in close proximity to each other, so that the already held workpiece 30 does not fall from a relatively high position and no impact is applied to the workpiece 30. In this way, if the hand 40A of the first configuration example or the hand 40D of the fourth configuration example is used as the hand 40, it is possible to prevent the already held workpiece 30 from falling and applying an impact to the workpiece 30 when grasping the second or subsequent workpieces 30.

[0047] <Modifications regarding hand configuration> The configuration of the hand 40 can be modified by adding a mechanism for preventing the workpiece 30 from dropping when the tip of the robot arm 20 is moved while gripping the workpiece 30, that is, while the workpiece 30 is being transported. An example of such a modification will be described with reference to Figs. 20 to 22. As shown in Figs. 20 and 21, a hand 40F of this modification has four support parts 46, 47, 48, and 49 added to the hand 40A of the first configuration example.

[0048] The support parts 46-49 are each formed of a rectangular plate-like member. As shown in Fig. 21, the support parts 46-49 are provided so as to support two of the four side surfaces 33 of the workpiece 30 excluding the main surface when the workpiece 30 is gripped. The remaining two of the side surfaces 33 are supported by the claw parts 41A and 42A of the hand 40F. According to the hand 40F of this modification, when the workpiece 30 is gripped, all four sides of the workpiece 30 are covered by the components of the hand 40F including the support parts 46-49, so that the workpiece 30 is prevented from dropping during transportation.

[0049] Moreover, according to the hand 40F of this modification, the workpiece 30 can be pressed from all sides simply by gripping the workpiece 30 due to the structure of the hand 40F, so that the three workpieces 30 can be arranged uniformly, and as a result, the three workpieces 30 can be stacked in an aligned state. Furthermore, according to the hand 40F of this modification, even if the workpieces 30 are slightly misaligned from each other as shown in the left side of Fig. 22 when all the workpieces 30 are gripped, by moving the tip of the robot arm 20 to a position above the placement location in that state and suddenly stopping it at the position above the placement location, an inertial force acts on the workpieces 30, so that the three workpieces 30 can be stacked in an aligned state reliably as shown in the right side of Fig. 22.

[0050] (Other embodiments) The present invention is not limited to the embodiments described above and shown in the drawings, and can be modified, combined, or expanded as desired without departing from the spirit and scope of the present invention. The numerical values ​​and the like shown in the above embodiment are merely examples and are not intended to be limiting.

[0051] The robot arm 20 does not have to be configured as a horizontal multi-joint type robot, and various types of robot arms can be used, such as a vertical multi-joint type robot having an arm with six or seven axes.

[0052] Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure. [Explanation of symbols]

[0053] 10...stacking system, 20...robot arm, 30, 30a, 30b, 30c...workpiece, 31, 32...main surface, 33...side surface, 40, 40A, 40B, 40C, 40D, 40E, 40F...hand, 41A, 41B, 41C, 41D, 41E, 42A, 42B, 42C, 42D...jaw portion, 43A, 43B, 43C, 43D, 43E, 44A, 44B, 44C, 44D, 44E, 45E...mounting portion, 46, 47, 48, 49...support portion, 50...control device.

Claims

1. A system for stacking a plurality of workpieces placed at separate acquisition locations at a predetermined placement location using a robot arm, comprising: The robot arm has a hand attached to its tip for gripping the workpiece; A control device for controlling the operation of the robot arm; Equipped with The hand is structured so as to be able to simultaneously grasp all of the workpieces stacked in multiple stages, The control device includes: a gripping process in which a tip end of the robot arm is moved to the vicinity of the acquisition location and each of the plurality of workpieces is gripped by the hand one by one; a placement process in which all of the plurality of workpieces are grasped by the hand by repeatedly executing the grasping process, and then a tip end of the robot arm is moved to the vicinity of the placement location, and all of the plurality of workpieces are placed at the placement location while maintaining the state in which they are stacked in multiple layers; A stacking system that performs the above.

2. The workpiece has a flat plate shape having two main surfaces facing each other, When one of two mutually orthogonal directions along the main surface is defined as a left-right direction and the direction orthogonal to the main surface is defined as a top-bottom direction, The hand includes two claws that move in parallel in the left-right direction to open and close, The two claws have a mounting portion at the tip thereof, the mounting portion having a shape extending along the left-right direction. The control device includes: In the gripping process, A process of moving the hand to a position above a target workpiece that is a target workpiece to be grasped; a process of opening the two claw portions in a left-right direction and moving the hand downward; A process of placing the target work on the placement section by closing the two claw portions along the left-right direction; 2. The stacking system according to claim 1, further comprising:

3. The workpiece has a flat plate shape having two main surfaces facing each other, When one of two mutually orthogonal directions along the main surface is defined as a left-right direction and the direction orthogonal to the main surface is defined as a top-bottom direction, The hand includes two claws that move in parallel in the left-right direction to open and close, The two claws have a mounting portion at the tip thereof, the mounting portion having a shape extending along the left-right direction. The mounting portion is configured so that its tip portion can rotate upward around its base end portion, The control device includes: In the gripping process, A process of moving the hand to a position above a target workpiece that is a target workpiece to be grasped; A process of placing the target work on the placement section by moving the hand downward; 2. The stacking system according to claim 1, further comprising:

4. The stacking system according to claim 2 , wherein a vertical dimension of the placement portion is smaller than a vertical dimension of the workpiece.

5. The workpiece has a flat plate shape having two main surfaces facing each other, When one of two mutually orthogonal directions along the main surface is defined as a left-right direction and the direction orthogonal to the main surface is defined as a top-bottom direction, The hand includes one claw portion, A plurality of placement portions each having a shape extending in the left-right direction are provided at the tip of the claw portion so as to be stacked in the up-down direction, Each of the plurality of placement sections is configured to be movable in the up-down direction and the left-right direction, The control device includes: In the gripping process, A process of moving the hand to a position above a target workpiece that is a target workpiece to be grasped; a process of placing the target work on the placement section by moving the hand downward and left and right; A process of moving the placement unit on which the target work is placed in an upward direction; Run In the arrangement process, The stacking system according to claim 1 , further comprising a process of tilting the hand in a vertical direction or a process of removing the plurality of placement units from the hand by moving the placement units in a horizontal direction.

6. The stacking system according to claim 2 , wherein the hand is provided with a support portion that supports a side surface of the workpiece other than the main surface when the hand is gripping the workpiece.

7. A method for stacking a plurality of workpieces placed at acquisition locations separated from each other at a predetermined placement location using a robot arm, comprising the steps of: The robot arm has a hand attached to its tip for gripping the workpiece, The hand is structured so as to be able to simultaneously grasp all of the workpieces stacked in multiple stages, a gripping process in which a tip end of the robot arm is moved to the vicinity of the acquisition location and each of the plurality of workpieces is gripped by the hand one by one; a placement process in which all of the plurality of workpieces are grasped by the hand by repeatedly executing the grasping process, and then a tip end of the robot arm is moved to the vicinity of the placement location, and all of the plurality of workpieces are placed at the placement location while maintaining the state in which they are stacked in multiple layers; A stacking method for performing the above.

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