Workpiece conveyance device and workpiece conveyance program

Abstract

To provide a workpiece conveyance device and a workpiece conveyance program capable of appropriately bringing a suction part into contact with a workpiece.SOLUTION: A workpiece conveyance device 10 sucks and lifts a workpieces to convey the workpiece. The workpiece conveyance device 10 includes: a hand part 20; servo motors 91 to 93 that move the hand part 20; and a control device 100 that controls the servo motors 91 to 93. The hand part 20 includes: a suction pad including a suction surface that sucks the workpiece; a connection part to be connected to the workpiece conveyance device 10; and a floating mechanism that is arranged between the connection part and the suction pad and causes the suction surface to follow the workpiece W. When the hand part 20 is lowered by a Z-axis servo motor 93 and the suction surface is brought into contact with the workpiece W, the control device 100 controls the servo motors 91, 92 so as to set a free state where a torque is not generated in one of horizontal directions with respect to the hand part 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a workpiece transport device and a workpiece transport program. [Background technology]

[0002] Conventionally, a palletizing robot or a handling robot has been used to automate the depalletizing work (or palletizing work, the same applies below) of bags and the like. As a robot hand used for automating such a depalletizing work, for example, the one described in Patent Document 1 is known.

[0003] The robot hand described in Patent Document 1 brings a suction pad into contact with the workpiece to be depalletized, and then applies a vacuum suction force to the suction pad via the chamber to which it is connected, thereby adsorbing and lifting the workpiece with the suction pad, and transporting it in this lifted state.

[0004] Incidentally, workpieces such as bags containing rice, grains, etc. are intangible and easily deformed. For this reason, when stacked on a pallet, the load may collapse inward or may break and collapse outward due to an error in the loading and unloading position during palletizing (stacking) work or vibration during transportation. In other words, all the workpieces may not be stacked regularly. If the position of the robot hand cannot be controlled so that the suction pad abuts on the center of the workpiece, the workpiece W will be lifted by eccentric suction at a part that is offset from the center. If the magnitude of the moment generated in the workpiece due to the offset exceeds the suction force of the suction pad, the workpiece may come off the suction pad and fall during depalletizing work.

[0005] Therefore, the robot hand in Patent Document 2 is provided with a moment detection means for detecting the moment caused by the eccentricity of the workpiece held by the suction pad, and a control unit for changing the suction position of the suction pad on the workpiece based on the moment detected by the moment detection means, thereby enabling the suction pad to reliably pick up the center of gravity of the workpiece. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-80370 [Patent Document 2] Japanese Patent Application Publication No. 9-262786 Summary of the Invention [Problem to be solved by the invention]

[0007] However, not only may the bag or other workpiece be misaligned, but the top surface may not be horizontal. That is, the shape of the bag or other workpiece containing rice or grains may change due to the movement of the contents, and the top surface may be inclined relative to the horizontal plane.

[0008] In this case, even if the suction pad is pressed vertically downward against the workpiece, a gap may occur because the upper surface of the workpiece is inclined, reducing the suction force and making it impossible to suction the workpiece stably.

[0009] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a work transport device and a work transport program that can properly abut the suction portion against the workpiece even if there is variation in the workpiece posture. [Means for solving the problem]

[0010] A workpiece transport device for solving the above problems is provided. A workpiece conveying device that adsorbs a workpiece, which is a bag containing a liquid, a powder, or a granular material, and lifts and conveys the workpiece, A robot hand and A first drive unit that moves the robot hand in a vertical direction; A second drive unit that moves or rotates the robot hand in a horizontal direction; a drive control unit that controls the first drive unit and the second drive unit, The robot hand includes: A suction unit having a suction surface that generates negative pressure to suction the surface of the workpiece; A connection portion connected to the workpiece transport device; a floating mechanism disposed between the connection portion and the suction portion and adapted to cause an adsorption surface of the suction portion to follow the surface of the workpiece; The drive control unit is When the first drive unit lowers the robot hand and brings the suction surface into contact with the surface of the workpiece, the second drive unit is controlled to set the robot hand to a free state in which no torque is generated in any horizontal direction.

[0011] This allows the suction portion to properly abut against the surface of the workpiece and ensure stable suction even if the workpiece has varying postures.

[0012] A workpiece transport program for solving the above problems includes: A workpiece conveying program for a workpiece conveying device that adsorbs a workpiece, which is a bag containing a liquid, a powder, or a granular material, and conveys the workpiece by lifting it up, The workpiece transport device is A robot hand and A first drive unit that moves the robot hand in a vertical direction; A second drive unit that moves or rotates the robot hand in a horizontal direction; a drive control unit that controls the first drive unit and the second drive unit, The robot hand includes: A suction unit having a suction surface that generates negative pressure to suction the surface of the workpiece; A connection portion connected to the workpiece transport device; a floating mechanism disposed between the connection portion and the suction portion and adapted to cause an adsorption surface of the suction portion to follow the surface of the workpiece; When the first drive unit lowers the robot hand and brings the suction surface into contact with the surface of the workpiece, the drive control unit executes a free control step of controlling the second drive unit to set a free state in which no torque is generated for the robot hand in any horizontal direction.

[0013] This allows the suction portion to properly abut against the surface of the workpiece and ensure stable suction even if the workpiece has varying postures. [Brief description of the drawings]

[0014] [Figure 1] FIG. [Diagram 2] FIG. 2 is a perspective view of the robot hand as viewed from above. [Diagram 3] FIG. 2 is a perspective view of the robot hand as viewed from below. [Figure 4] Front view of the robot hand. [Diagram 5] Side view of a robotic hand. [Figure 6] FIG. [Figure 7] Cross-sectional view of the floating mechanism taken along line AA. [Figure 8] FIG. 4 is a partial cross-sectional view showing an operation mode of the hand portion. [Figure 9] FIG. [Figure 10] FIG. 4 is a partial cross-sectional view showing an operation mode of the hand portion. [Figure 11] FIG. 11 is a cross-sectional view of a floating mechanism according to a modified example. [Figure 12] FIG. 11 is a block diagram showing the configuration of a control device in a second embodiment. [Figure 13]10 is a flowchart of a transport process according to a second embodiment. [Figure 14] 13 is a partial cross-sectional view showing an operation mode of a hand portion in the second embodiment. FIG. [Figure 15] 13 is a partial cross-sectional view showing an operation mode of a hand portion in the second embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of a "robot hand" according to the present invention will be described with reference to the drawings. In the following embodiments and modifications, parts that are the same or equivalent to each other are given the same reference numerals in the drawings, and the explanations of the parts with the same reference numerals are incorporated herein by reference. In addition to the combinations of configurations explicitly shown in the description of the embodiments and modifications, it is also possible to combine the embodiments and modifications as long as there is no particular problem with the combination.

[0016] (First embodiment) As shown in Fig. 1, the work transport device 10 is a device that sequentially transports workpieces W from a supply location and aligns and loads them on a portable pallet P installed at a predetermined position, that is, a device that performs palletizing. Note that the work transport device 10 is also a device that sequentially transports the workpieces W aligned and loaded on a portable pallet P installed at a predetermined position to a predetermined discharge location, that is, a device that performs depalletizing. When depalletizing is performed, the operations when palletizing are basically performed in reverse, so in this embodiment, palletizing will be mainly described.

[0017] As shown in Fig. 10, the workpiece W is a bag containing rice, grains, etc. The object contained in the bag may be a liquid, a powder, or a granular material, such as a raw material for plastics made of granular material, or wheat flour.

[0018] The workpiece W is supplied from an external conveying facility (such as a belt conveyor) to a roller conveyor 1 provided in the workpiece conveying device 10. The supplied workpiece W is then positioned and stopped at a predetermined rest position by a stopper (not shown) provided on the roller conveyor 1. The workpiece conveying device 10 is configured to detect the workpiece W positioned and stopped on the roller conveyor 1 by a sensor or the like, and to hoist and convey it.

[0019] When depalletizing is performed, the reverse operation of the palletizing described above is performed. That is, the workpieces W are lifted from the pallet P by the workpiece transport device 10 and discharged to an external transport facility via a roller conveyor 1 or the like.

[0020] Next, a detailed description will be given of the configuration of the workpiece transport device 10. As shown in Fig. 1, the workpiece transport device 10 includes a hand unit 20 serving as a robot hand for gripping a workpiece W, a transport mechanism 30 for moving the hand unit 20, and a rectangular parallelepiped frame 70 to which the transport mechanism 30 is fixed. The workpiece transport device 10 also includes a control device 100 for controlling the operations of the hand unit 20 and the transport mechanism 30, and a controller (not shown) serving as an information terminal capable of inputting and outputting various information.

[0021] In this embodiment, the longitudinal direction of the frame 70 is the X-axis direction, the lateral direction (the direction perpendicular to the X-axis) is the Y-axis direction, and the direction perpendicular to the X-axis and Y-axis directions is the Z-axis direction. Note that since the workpiece conveying device 10 is usually installed on a flat surface, the Z-axis direction corresponds to the up-down direction (vertical direction). Also, the X-axis direction and the Y-axis direction correspond to the horizontal direction.

[0022] The conveying mechanism 30 has a pillar portion 50 fixed to a frame body 70 and formed to extend along the Z-axis direction, and an arm portion 60 fixed to the pillar portion 50 and formed to extend along the Y-axis direction.

[0023] An X-axis guide rail 51 is provided on the frame 70 along the X-axis direction, and the pillar portion 50 is fixed to the X-axis guide rail 51 so as to be movable along the X-axis direction. The pillar portion 50 is drivingly connected to the output shaft of an X-axis servo motor 91 disposed at the bottom of the frame 70 via a toothed belt or the like. In other words, the pillar portion 50 is configured to reciprocate in the X-axis direction along the X-axis guide rail 51 based on the driving force of the X-axis servo motor 91.

[0024] A Z-axis guide rail 61 is provided on the pillar portion 50 along the Z-axis direction, and the arm portion 60 is fixed to the Z-axis guide rail 61 so as to be movable along the Z-axis direction. The arm portion 60 is drivingly connected to the output shaft of a Z-axis servo motor 93 provided on the pillar portion 50 via a toothed belt or the like. In other words, the arm portion 60 is configured to reciprocate in the Z-axis direction along the Z-axis guide rail 61 based on the driving force of the Z-axis servo motor 93.

[0025] A Y-axis guide rail 21 is provided on the arm unit 60 along the Y-axis direction, and the hand unit 20 is fixed to the Y-axis guide rail 21 so as to be movable along the Y-axis direction. The hand unit 20 is drivingly connected to the output shaft of a Y-axis servo motor 92 provided on the arm unit 60 via a toothed belt or the like. In other words, the hand unit 20 is configured to reciprocate in the Y-axis direction along the Y-axis guide rail 21 based on the driving force of the Y-axis servo motor 92.

[0026] As described above, the transport mechanism 30 is configured to be able to linearly move the hand unit 20 in two directions (X-axis direction and Y-axis direction) that are orthogonal to the horizontal direction, and in the vertical direction (Z-axis direction).

[0027] 1, the hand unit 20 is fixed to the arm unit 60 via a rotation mechanism 23 serving as a rotation unit. The rotation mechanism 23 is configured to be able to rotate the hand unit 20 around the Z axis (in the direction of arrow R in FIG. 1) with the rotation mechanism 23 as the center based on the driving force of a built-in rotation axis servo motor 94.

[0028] 2 and 3, the hand unit 20 has a connection part 24 connected to and fixed to the rotation mechanism 23, a suction pad 25 as a suction part, and a floating mechanism 80 arranged between the connection part 24 and the suction pad 25. The suction pad 25 is provided with its suction surface 25a facing downward. An ejector is connected to the suction pad 25 via an air pipe (not shown). The inside of the suction pad 25 becomes negative pressure due to the operation of the ejector, which makes it possible to suction the upper surface of the workpiece W. The contact part of the suction pad 25 is made of rubber or sponge and is configured to be able to absorb unevenness on the surface of the workpiece W to a certain extent.

[0029] The floating mechanism 80 is for causing the suction surface 25a of the suction pad 25 to follow the surface of the workpiece W (the upper surface in this embodiment), and will be described in detail later.

[0030] Next, the control device 100 will be described. The control device 100 is an electronic control device equipped with a known microcomputer including a CPU, a ROM, a RAM, a flash memory, etc. The control device 100 includes a drive circuit for driving the various servo motors 91-94 described above, and is configured to be able to control the operation of the various servo motors 91-94 via the drive circuit.

[0031] The control device 100 is connected to various sensors, various servo motors 91-94, a controller, etc., and is configured to be able to acquire various information. The control device 100 also has various functions, and executes the various functions based on the acquired information. These functions are realized by executing a program stored in a storage device (storage memory) included in the control device 100. The various functions may be realized by electronic circuits, which are hardware, or at least a part of them may be realized by software, that is, processing executed on a computer.

[0032] Among the various functions, for example, there is a palletizing function that transports the workpieces W and loads them on a pallet P. To briefly explain the palletizing function, the control device 100 detects the position of the workpieces W using a sensor or the like, lifts the workpieces W with the hand unit 20, moves the hand unit 20 together with the workpieces W onto the pallet P using the transport mechanism 30, and releases them, thereby loading the workpieces W. With this function, the workpieces W are stacked in multiple stages in the vertical direction (Z-axis direction) on the pallet P. At that time, the workpieces W may be stacked in multiple rows in each stage in a predetermined direction (X-axis direction or Y-axis direction).

[0033] Among the various functions, for example, there may be a depalletizing function that transports the workpieces W loaded on the pallet P one by one. Briefly explaining the depalletizing function, it is a function that detects the position of each workpiece W loaded on the pallet P using a sensor or the like, lifts the workpiece W whose position has been detected using the hand unit 20, and transports it from the pallet P to a predetermined discharge location.

[0034] Incidentally, the workpiece W in this embodiment is a bag containing rice, grains, etc., as described above. Therefore, although the workpiece W maintains its shape to some extent due to the bag, the shape may change due to the movement of the contents, and the upper surface may be inclined relative to the horizontal plane. In this case, with a conventional robot hand, even if a suction pad is pressed against the workpiece W so as to be perpendicular to the horizontal direction, a gap may occur because the upper surface of the workpiece W is inclined, the suction force may decrease, and stable suction may not be achieved.

[0035] In the hand unit 20 of this embodiment, a floating mechanism 80 is provided between the connection portion 24 and the suction pad 25, which causes the suction surface 25a of the suction pad 25 to follow the surface (the upper surface in this embodiment) of the workpiece W. Hereinafter, the floating mechanism 80 will be described in detail with reference to Figs. 2 to 7.

[0036] As shown in Figures 2 and 4, the floating mechanism 80 comprises a first plate 81 fixed to the connection portion 24, a second plate 82 to which the suction pad 25 is fixed and which faces the first plate 81 (in the vertical direction in Figure 4), shafts 83a to 83c arranged upright on the second plate 82, and a coil spring 84 as an elastic body disposed between the first plate 81 and the second plate 82 and applying an elastic force in the direction in which they move apart.

[0037] The first plate 81 is configured in a disk shape as shown in Fig. 6. As shown in Fig. 2 and Fig. 4, the first plate 81 is disposed above the hand unit 20 in the vertical direction (Z-axis direction), and the connection unit 24 is attached to the upper surface thereof.

[0038] As shown in FIG. 7, the first plate 81 has tapered holes 81a to 81c that penetrate the first plate 81 in the vertical direction in FIG. 7. The tapered holes 81a to 81c have tapered surfaces that become smaller in diameter toward the second plate 82 (i.e., toward the bottom). The inclination angle α (the elevation angle with respect to the horizontal direction, see FIG. 7) of the tapered surfaces of the tapered holes 81a to 81c is set within a range of 45 to 60 degrees, and is set to 45 degrees in this embodiment. As shown in FIG. 6, the tapered holes 81a to 81c are provided in three locations, and are arranged so that the distance between the centers of the tapered holes 81a to 81c is equal to each other. In other words, the tapered holes 81a to 81c are arranged so that the centers of the tapered holes 81a to 81c are located at the vertices of an equilateral triangle.

[0039] 2 and other figures, the second plate 82 is configured in a long plate shape, and is disposed below the first plate 81 in the vertical direction, facing the first plate 81 in the vertical direction. The suction pad 25 is fixed to the lower surface of the second plate 82, and shafts 83a to 83c are provided upright on the upper surface of the second plate 82.

[0040] 2 and 6, three shafts 83a to 83c are provided and are arranged at positions corresponding to the tapered holes 81a to 81c of the first plate 81. That is, the shafts 83a to 83c are arranged so that the distance between the centers of the shafts 83a to 83c is equal to each other and is the same as the distance between the centers of the tapered holes 81a to 81c. In other words, the shafts 83a to 83c are arranged so that the central axes of the shafts 83a to 83c are located at the vertices of an equilateral triangle.

[0041] 4 and 7, the shafts 83a to 83c are each formed in a rod shape and are fixed so as to be perpendicular to the upper surface of the second plate 82. In other words, when the second plate 82 is disposed opposite to the first plate 81, the shafts 83a to 83c are shaped to extend from the second plate 82 toward the first plate 81. The tips of the shafts 83a to 83c (the ends opposite to the second plate 82) are inserted into the tapered holes 81a to 81c of the first plate 81.

[0042] 7, the tips of the shafts 83a to 83c to be inserted into the tapered holes 81a to 81c are provided with tapered sections 85 having a generally truncated cone shape with a tapered surface corresponding to the shape of the tapered holes 81a to 81c. The tapered sections 85 are accommodated inside the tapered holes 81a to 81c and are provided so as to be able to be engaged with the tapered holes 81a to 81c.

[0043] More specifically, the tapered portion 85 is formed so that the diameter becomes smaller toward the second plate 82, that is, the diameter becomes larger as it moves away from the second plate 82. The outer diameter of the small diameter portion (lower portion) of the tapered portion 85 is equal to or larger than the diameter R3 of the small diameter portion of the tapered holes 81a to 81c. In this embodiment, the outer diameter of the small diameter portion of the tapered portion 85 is set to be slightly larger than the diameter R3 of the small diameter portion of the tapered holes 81a to 81c. The outer diameter R2 of the large diameter portion (upper portion) of the tapered portion 85 is formed to be larger than at least the diameter R3 of the small diameter portion of the tapered holes 81a to 81c. Therefore, the tapered portion 85 is locked by the tapered holes 81a to 81c.

[0044] As described above, the tapered portion 85 has a tapered surface corresponding to the shape of the tapered holes 81a to 81c, and therefore the inclination angle α of the tapered surface of the tapered portion 85 is the same as the inclination angle α of the tapered surfaces of the tapered holes 81a to 81c. That is, the inclination angle α of the tapered surface of the tapered portion 85 in this embodiment is set to 45 degrees. Therefore, as shown in FIG. 7, when the direction of the shafts 83a to 83c is along the vertical direction, the tapered portion 85 comes into surface contact with the tapered holes 81a to 81c. Therefore, when the tapered portion 85 is engaged with the tapered holes 81a to 81c, it is stably engaged.

[0045] Furthermore, the vertical length dimension L1 of the tapered portion 85 is shorter than the vertical length dimension L2 of the tapered holes 81a to 81c, and in this embodiment, is approximately half the length dimension. The outer diameter R2 of the large diameter portion of the tapered portion 85 is smaller than the diameter R4 of the large diameter portion of the tapered holes 81a to 81c. That is, when the tapered portion 85 is engaged with the tapered holes 81a to 81c, a gap (clearance) is provided above the tapered portion 85. Therefore, the shafts 83a to 83c are vertically movable relative to the first plate 81, and are configured to be able to be inserted into and removed from the tapered holes 81a to 81c.

[0046] 7, the diameter R1 of the shafts 83a to 83c is smaller than the diameter R3 of the small diameter portion of the tapered holes 81a to 81c. Specifically, the diameter R1 of the shafts 83a to 83c is about half the diameter R3 of the small diameter portion of the tapered holes 81a to 81c. The tapered portions 85 attached to the ends of the shafts 83a to 83c are housed in the tapered holes 81a to 81c, which have a larger diameter as they move away from the second plate 82.

[0047] From the above, in a state in which the tapered portion 85 is pressed toward the first plate 81 side (the side opposite to the second plate 82), the shafts 83a to 83c are able to move a predetermined distance in the horizontal direction. In addition, as shown in Fig. 9, in a state in which the tapered portion 85 is pressed toward the first plate 81 side, the shafts 83a to 83c are able to incline at a predetermined angle (indicated by angle β in Fig. 9). In other words, when the tapered portion 85 is pressed toward the first plate 81 side, the shafts 83a to 83c are configured to be able to swing relative to the first plate 81.

[0048] Next, the coil spring 84 will be described. As shown in Fig. 2 and Fig. 7, the coil spring 84 is a compression coil spring disposed between the first plate 81 and the second plate 82, and applies elastic force in the direction in which they move apart. The coil spring 84 is attached to the outside of each of the shafts 83a to 83c. In other words, the shafts 83a to 83c are disposed inside the coil spring 84.

[0049] As shown in FIG. 7, the coil spring 84 has a spring receiving portion 86 for the coil spring at the end on the second plate 82 side of both ends. The spring receiving portion 86 has a cylindrical portion 87 and a flange portion 88 provided on the outer periphery of the cylindrical portion 87. The shafts 83a to 83c are inserted into the inside of the cylindrical portion 87. The cylindrical portion 87 is adapted to move along the shafts 83a to 83c. The end of the coil spring 84 on the second plate 82 side is attached to the outside of the cylindrical portion 87 and abuts (presses) against the second plate 82 via the flange portion 88. The outer diameter of the cylindrical portion 87 is approximately the same as the inner diameter of the coil spring 84. Therefore, the end of the coil spring 84 is prevented from shifting laterally (i.e., outward) relative to the cylindrical portion 87.

[0050] The outer diameter of the flange portion 88 is formed to be larger than that of the coil spring 84. As a result, the coil spring 84 exerts an elastic force on the second plate 82 via the flange portion 88 of the spring receiving portion 86. At this time, since the end portion of the coil spring 84 is configured not to shift laterally relative to the cylindrical portion 87, an elastic force is applied in the direction in which the shafts 83a to 83c extend, i.e., in the direction perpendicular to the second plate 82.

[0051] On the other hand, at least the end of the coil spring 84 on the first plate 81 side is in direct contact with the first plate 81 and exerts an elastic force directly on the first plate 81. At this time, the coil spring 84 exerts an elastic force along the direction in which the shafts 83a to 83c extend, and as described above, the shafts 83a to 83c are tiltable with respect to the first plate 81. As shown in FIG. 8 and FIG. 9, when the shafts 83a to 83c are tilted with respect to the first plate 81, the distance between the first plate 81 and the second plate 82 becomes shorter, and therefore the elastic force of the coil spring 84 also becomes larger. As a result, the tapered portion 85 engages with the tapered holes 81a to 81c, and the coil spring 84 exerts an elastic force so that the first plate 81 and the second plate 82 are parallel to each other.

[0052] The inner diameter of the coil spring 84 is larger than the diameter of the small diameter portion of the tapered holes 81a-81c. The end of the coil spring 84 on the second plate 82 side is prevented from shifting laterally relative to the shafts 83a-83c by the spring receiving portion 86, and therefore the end of the coil spring 84 on the first plate 81 side is also prevented from shifting laterally much relative to the shafts 83a-83c. Therefore, even if the shafts 83a-83c are inclined relative to the first plate 81 as shown in Fig. 9, the coil spring 84 is prevented from entering the tapered holes 81a-81c.

[0053] Next, the operation of the floating mechanism 80 when the workpiece W is lifted by the hand unit 20 will be described with reference to Figs. 8 to 10. Note that the description will be given on the assumption that the upper surface of the workpiece W to be transported is inclined with respect to the horizontal direction. Also, Figs. 8 to 10 show the floating mechanism 80 in cross section. For convenience of explanation, the suction pads 25 are illustrated in a simplified manner, and the connection parts 24 are not illustrated.

[0054] After detecting the workpiece W, the control device 100 moves the hand unit 20 downward in the vertical direction (Z-axis direction) to press the suction surface 25a of the suction pad 25 against the workpiece W. That is, the suction surface 25a in a horizontal state is pressed against the upper surface of the workpiece W that is inclined with respect to the horizontal direction.

[0055] At this time, as shown in Figs. 8 and 9, depending on the posture of the workpiece W, some or all of the shafts 83a to 83c are pressed into the tapered holes 81a to 81c of the first plate 81. Since the elastic force of the coil spring 84 is exerted in the direction in which the first plate 81 and the second plate 82 are separated from each other, even if some of the shafts 83a to 83c are pressed in, all of the shafts 83a to 83c are not pressed in the same manner. As a result, the shafts 83a to 83c are inclined relative to the first plate 81, and the second plate 82 is inclined. Accordingly, the suction surface 25a of the suction pad 25 to which the second plate 82 is fixed is inclined according to the upper surface of the workpiece W. In other words, the suction surface 25a follows the upper surface of the workpiece W and abuts thereon without any gap.

[0056] After the contact, the control device 100 generates a negative pressure to cause the suction pads 25 to suction the workpiece W. After suction, the control device 100 moves the hand unit 20 upward. As shown in FIG. 10, when the hand unit 20 is moved upward, the weight of the workpiece W and the elastic force of the coil spring 84 cause the shafts 83a to 83c to be pulled out from the tapered holes 81a to 81c until the tapered portions 85 are engaged with the tapered holes 81a to 81c. When the shafts 83a to 83c are pulled out and the tapered portions 85 are engaged with the tapered holes 81a to 81c, the second plate 82 becomes horizontal, and the workpiece W being lifted also becomes horizontal.

[0057] The control device 100 moves the hand unit 20 upward, and then moves it horizontally. At this time, the tapered portion 85 comes into surface contact with the tapered holes 81a to 81c, so even if the workpiece W is moved horizontally, vibration is suppressed and the workpiece W is kept horizontal. This allows the workpiece W to be moved stably in the horizontal direction.

[0058] According to the above embodiment, the following effects can be obtained.

[0059] A floating mechanism 80 is provided between the connection part 24 and the suction pad 25, which allows the suction surface 25a of the suction pad 25 to follow the surface of the workpiece W. As a result, even if the posture of the workpiece W varies, the suction pad 25 can be appropriately abutted against the surface of the workpiece W and stably adsorbed.

[0060] The shafts 83a to 83c are configured to be able to be inserted and removed from the tapered holes 81a to 81c and to be able to swing, and are provided with a coil spring 84 that applies an elastic force in a direction in which the first plate 81 and the second plate 82 are separated from each other. As a result, when the hand unit 20 is moved downward and the suction pad 25 is pressed against the workpiece W, some or all of the shafts 83a to 83c can be pushed into the tapered holes 81a to 81c according to the inclination of the surface of the workpiece W. As a result, the suction surface 25a of the suction pad 25 can be inclined according to the upper surface of the workpiece W. Note that, since the elastic force of the coil spring 84 is exerted in a direction in which the first plate 81 and the second plate 82 are separated from each other, even if some of the shafts 83a to 83c are pressed in, all of the shafts 83a to 83c are not pressed in the same way, and can be appropriately inclined according to the upper surface of the workpiece W.

[0061] Further, a tapered portion 85 having a tapered surface corresponding to the shape of the tapered holes 81a to 81c is provided at the tip of the shafts 83a to 83c, and is housed in the tapered holes 81a to 81c. As a result, when the hand unit 20 is moved upward after the workpiece W is attracted, the tapered portion 85 is engaged with the tapered holes 81a to 81c by the weight of the workpiece W and the elastic force of the coil spring 84, and the second plate 82 and the workpiece W can be kept in a horizontal state. Therefore, the workpiece W can be moved in the horizontal direction in a stable state. When the tapered portion 85 is engaged with the tapered holes 81a to 81c, it is in surface contact, so that vibration can be suppressed and a stable state can be maintained.

[0062] The vertical length dimension L2 of the tapered holes 81a to 81c is made longer than the vertical length dimension L1 of the tapered portion 85, and the size (diameter R4) of the large diameter portion of the tapered holes 81a to 81c is made larger than the size (outer diameter R2) of the large diameter portion of the tapered portion 85. This allows the tapered portion 85 to move into the gaps in the tapered holes 81a to 81c by pushing the shafts 83a to 83c into the tapered holes 81a to 81c. At this time, the tapered portion 85 can be moved in the horizontal direction within the range of the tapered holes 81a to 81c. As a result, it becomes possible to swing the shafts 83a to 83c relative to the first plate 81.

[0063] Furthermore, since the diameter R1 of the shafts 83a-83c is made smaller than the diameter R3 of the small diameter portions of the tapered holes 81a-81c, there is a margin before the shafts 83a-83c come into contact with the tapered holes 81a-81c, and the tiltable angle of the shafts 83a-83c can be increased.

[0064] A spring receiving portion 86 for the coil spring is provided at the end of the coil spring 84 on the second plate 82 side of both ends. The outer diameter of a cylindrical portion 87 of the coil spring 84 is set to be substantially the same as the inner diameter of the coil spring 84, so that the end of the coil spring 84 does not shift laterally relative to the cylindrical portion 87. This makes it possible to prevent the end of the coil spring 84 on the first plate 81 side from shifting laterally relative to the shafts 83a to 83c. Therefore, even if the shafts 83a to 83c are inclined relative to the first plate 81, the coil spring 84 can be prevented from entering the tapered holes 81a to 81c.

[0065] Three shafts 83a to 83c are provided and are not arranged in a straight line, which makes it easy to tilt the second plate 82 in the rotation direction about the X-axis and the rotation direction about the Y-axis.

[0066] Three shafts 83a to 83c are provided and arranged so that the distance between each of the shafts 83a to 83c is equal. This allows the inclination angle to be larger than when four or more shafts 83a to 83c are provided. Also, all of the shafts 83a to 83c are arranged so as to fit within the surface area of ​​the workpiece W. This allows the inclination angle to be larger while still being compact.

[0067] (Modification) A modified example in which the floating mechanism 80 in the above embodiment is partially modified will be described below.

[0068] In the above embodiment, as shown in FIG. 11, a spring receiving portion 101 for the coil spring may be provided at the end of the coil spring 84 on the first plate 81 side. The spring receiving portion 101 has a cylindrical portion 102 and a flange portion 103 provided on the outer periphery of the cylindrical portion 102, similar to the spring receiving portion 86. The shafts 83a to 83c are inserted into the inside of the cylindrical portion 102. However, the inner diameter R3 of the cylindrical portion 102 is larger than the inner diameter of the cylindrical portion 87 of the spring receiving portion 86 on the second plate 82 side. The inner diameter R10 of the cylindrical portion 102 is configured to be sufficiently larger than the diameter R1 of the shafts 83a to 83c. Therefore, a gap is provided so that the shafts 83a to 83c can move laterally relative to the cylindrical portion 102.

[0069] 11(b), when the shafts 83a to 83c are pressed into the tapered holes 81a to 81c, the shafts 83a to 83c can tilt with respect to the cylindrical portion 102. In other words, the spring receiving portion 101 does not interfere with the tilting of the shafts 83a to 83c.

[0070] The outer diameter shape of the spring receiving portion 101 is substantially the same as that of the spring receiving portion 86. This allows the coil spring 84 to exert an elastic force on the first plate 81 via the flange portion 103 of the spring receiving portion 101. In addition, the outer diameter shape of the flange portion 103 is configured to be larger than the outer diameters of the small diameter portions of the tapered holes 81a to 81c, so that it is possible to reliably prevent the coil spring 84 from entering the tapered holes 81a to 81c.

[0071] Furthermore, the spring receiving portion 101 on the first plate side is in slidable contact with the first plate 81. That is, the spring receiving portion 101 is configured to be slidable in the direction of the arrow T in Fig. 11. Therefore, when the shaft 83 is tilted, the spring receiving portion 101 slides and does not interfere with the cylindrical portion 102 of the spring receiving portion 101, and the tilt angle can be increased.

[0072] In the above embodiment, as shown in FIG. 11, the inclination angle of the tapered surfaces of the tapered holes 81a to 81c and the tapered portion 85 may be changed to 60 degrees.

[0073] In the above embodiment, the number and arrangement of the shafts 83a to 83c and the tapered holes 81a to 81c may be changed as desired.

[0074] Second embodiment A second embodiment, which is a partial modification of the first embodiment, will be described. In the second embodiment, the mechanical configuration of the workpiece transport device 10 is the same as that in the first embodiment, so the same reference numerals are used and the description will be omitted. In the second embodiment, the processing contents and control contents by the control device 100 will be mainly described.

[0075] As shown in FIG. 12, the control device 100 is connected to various servo motors 91-94 and an ejector 95. The control device 100 controls the drive of the various servo motors 91-94 to move the hand unit 20 along the X-axis direction, the Y-axis direction, or the Z-axis direction, or to turn (rotate) the hand unit 20 around a turning axis (rotation axis). Therefore, in this embodiment, the control device 100 functions as a drive control unit. In this embodiment, the Z-axis servo motor 93 constitutes a first drive unit that moves the hand unit 20 in the vertical direction. In addition, the X-axis servo motor 91, the Y-axis servo motor 92, and the turning axis servo motor 94 constitute a second drive unit that moves or rotates the hand unit 20 in the horizontal direction.

[0076] Furthermore, the control device 100 can control the operation of the ejector 95 to cause the suction pad 25 to suction the upper surface of the workpiece W or release the suction. Although not shown, the control device 100 is connected to various sensors, and grasps the position of the workpiece W based on the detection results from the various sensors, and controls the drive of the various servo motors 91-94 and the operation of the ejector 95.

[0077] Next, a description will be given of the processing contents of the control device 100 when the workpiece W is lifted by the hand unit 20. The control device 100 performs the transfer processing shown in Fig. 13 by executing a workpiece transfer program 97 stored in a storage device 96 provided in the control device 100. The transfer processing will be described in detail below.

[0078] When the conveying process is performed, the control device 100 checks the position of the workpiece W to be conveyed from the detection results of various sensors, and moves the hand unit 20 in the horizontal direction so that the hand unit 20 is positioned above the workpiece W (step S101). More specifically, in step S101, the control device 100 drives and controls the X-axis servo motor 91 to move the hand unit 20 in the X-axis direction so that the positions of the workpiece W and the hand unit 20 match in the X-axis direction. The control device 100 also drives and controls the Y-axis servo motor 92 to move the hand unit 20 in the Y-axis direction so that the positions of the workpiece W and the hand unit 20 match in the Y-axis direction. The control device 100 also drives and controls the rotating axis servo motor 94 to rotate the hand unit 20 so that the longitudinal direction of the hand unit 20 is aligned with the longitudinal direction of the workpiece W.

[0079] Next, the control device 100 drives and controls the Z-axis servo motor 93 so as to lower the hand unit 20 toward the workpiece W (step S102). Then, the control device 100 sets a servo free state (free state) in which no torque is generated in any direction in the horizontal direction for the hand unit 20 when the suction surface 25a of the suction pad 25 is brought into contact with the surface of the workpiece W (step S103). Specifically, the control device 100 sets the servo free state so as not to generate torque in the horizontal direction by cutting off the current to the X-axis servo motor 91 (X-axis motor), the Y-axis servo motor 92 (Y-axis motor), and the swivel axis servo motor 94 (rotation axis motor). Step S103 in this embodiment corresponds to a free control step.

[0080] The servo-free state may be a state in which the horizontal movement or rotation is not restricted by the torque of the servo motors 91, 92, and 94, and the hand unit 20 (more specifically, the portion on the first plate 81 side) can freely move or rotate in the horizontal direction by an external force. For this reason, if no torque is generated, it is not necessarily necessary to cut off the current to the servo motors 91, 92, and 94.

[0081] Furthermore, the timing for setting the servo free state, i.e., the start timing of step S103, may be any timing from when the hand unit 20 starts to descend (i.e., after the start of step S102) until before the suction surface 25a of the suction pad 25 is brought into contact with the surface of the workpiece W. For example, the servo free state may be set when the distance between the hand unit 20 and the workpiece W is measured by a distance measuring sensor and the measured distance is equal to or less than a predetermined distance. Also, the servo free state may be set after a predetermined time has elapsed since the start of descent. Also, the servo free state may be set immediately after the start of descent.

[0082] The control device 100 controls the operation of the ejector 95 so as to adsorb the workpiece W after the suction surface 25a of the suction pad 25 is brought into contact with the surface of the workpiece W (step S104). After the suction, the control device 100 controls the drive of the Z-axis servo motor 93 so as to raise the hand unit 20 that has adsorbed the workpiece W (step S105). After the hand unit 20 that has adsorbed the workpiece W is raised, the control device 100 releases the servo-free state (step S106). The timing for releasing the servo-free state may be any timing from when the hand unit 20 starts to rise after the suction unit has adsorbed the workpiece to when the hand unit 20 moves or rotates in the horizontal direction after the lift is completed. For example, the servo-free state may be released after a predetermined time has elapsed since the lift was started, so that the hand unit 20 does not move or rotate in the horizontal direction.

[0083] After the lift is complete, the control device 100 moves the hand unit 20 horizontally to a predetermined position (on the pallet P or to the destination on the roller conveyor 1) (step S107). That is, the control device 100 drives and controls the X-axis servo motor 91, etc. to move the hand unit 20. After moving the hand unit 20 to the predetermined position, the control device 100 lowers the hand unit 20, releases suction, and completes the transport of the workpiece W (step S108). Then, the transport process ends.

[0084] The effect of setting the servo-free state will be described with reference to Figs. 14 and 15. Note that the explanation will be given on the premise that the top surface of the workpiece W to be transported shown in Figs. 14 and 15 is more inclined than the top surface of the workpiece W shown in Fig. 8. Also, Figs. 14 to 15 show a cross section of the floating mechanism 80. For convenience of explanation, the suction pads 25 are illustrated in a simplified manner, and the connection parts 24 are not illustrated.

[0085] After detecting the workpiece W, the control device 100 lowers the hand unit 20 to press the suction surface 25a of the suction pad 25 against the workpiece W. At this time, depending on the posture of the workpiece W, as shown in Fig. 14, some or all of the shafts 83a to 83c are pressed into the tapered holes 81a to 81c of the first plate 81. Note that since the elastic force of the coil spring 84 is exerted in the direction in which the first plate 81 and the second plate 82 move away from each other, even if some of the shafts 83a to 83c are pressed in, all of the shafts 83a to 83c are not pressed in in the same manner.

[0086] As a result, the shafts 83a-83c are inclined relative to the first plate 81, and the second plate 82 is inclined. When the shafts 83a-83c are inclined to a certain extent, the tapered portions 85 come into contact with the inclined surfaces of the tapered holes 81a-81c, or the shafts 83a-83c come into contact with the small diameter portions of the tapered holes 81a-81c.

[0087] At this time, in the above first embodiment, the horizontal movement and rotation of the hand portion 20, more specifically the portion on the side of the first plate 81, was restricted by the torque of the servo motors 91, 92, 94, so that the shafts 83a to 83c engaged with the tapered holes 81a to 81c and did not tilt any further.

[0088] However, in the second embodiment, a servo-free state is set for each of the servo motors 91, 92, and 94. Therefore, when the shafts 83a to 83c are tilted to a certain extent, the portions on the first plate 81 side move horizontally as shown by the arrows in Fig. 15 due to interference with the tapered holes 81a to 81c or due to the elastic force of the coil spring 84. This allows the shafts 83a to 83c to be tilted further.

[0089] Accordingly, the second plate 82 and the suction pad 25 fixed thereto are also further inclined with respect to the first plate 81. Therefore, the suction surface 25a can be made to more closely follow the inclination of the upper surface of the workpiece W and come into contact with it without any gaps.

[0090] According to the second embodiment, the following effects can be obtained.

[0091] When the control device 100 lowers the hand unit 20 and brings the suction surface 25a into contact with the surface (top surface) of the workpiece W, it sets a servo-free state in which no torque is generated in the horizontal direction for the hand unit 20. This allows the inclination angle to be increased in the floating mechanism 80. Therefore, the suction surface 25a can be made to more closely follow the inclination of the top surface of the workpiece W and come into contact with it without any gaps.

[0092] The control device 100 sets the servo-free state by cutting off the current to the servo motors 91, 92, and 94 when the suction surface 25a is brought into contact with the upper surface of the workpiece W. Therefore, the servo-free state can be set by simple control with low power consumption. In addition, because movement in the X-axis and Y-axis directions and rotation are permitted, the workpiece W can be made to follow any posture of the upper surface of the workpiece W.

[0093] The control device 100 sets the servo free state before the suction surface 25a is brought into contact with the upper surface of the workpiece W. In addition, the servo free state is released after the suction pad 25 has adsorbed the workpiece W. Therefore, when the shafts 83a to 83c tilt, the portion on the first plate 81 side can be reliably made movable without being hindered by the torque of the servo motors 91, 92, and 94.

[0094] The shafts 83a to 83c are configured to be able to move in and out of the tapered holes 81a to 81c, to be able to swing, and are provided with a coil spring 84 that applies an elastic force in a direction in which the first plate 81 and the second plate 82 move apart. Therefore, when the inclination angle of the upper surface of the workpiece W is large, the elastic force of the coil spring 84 allows the portion on the first plate 81 side to slide smoothly, and the shafts 83a to 83c can be easily inclined.

[0095] In addition, by setting the servo-free state and configuring the floating mechanism 80, the suction surface 25a is tilted to follow the upper surface of the workpiece W. Therefore, no power is consumed for tilting, and no special control is required.

[0096] The transfer process by the control device 100 and the workpiece transfer program 97 described in the second embodiment may be applied in combination with the first embodiment or the modified example.

[0097] In the second embodiment, the servo free state is set for all of the X-axis servo motor 91, the Y-axis servo motor 92, and the rotation axis servo motor 94, but it is also possible to set the servo free state for only one of them. In other words, it is also possible to set a servo free state in which no torque is generated in any of the horizontal directions.

[0098] Below, technical ideas that can be derived from the above embodiment and modified examples will be described. [Configuration 1] A robot hand used in a workpiece conveying device that adsorbs a workpiece, which is a bag containing a liquid, a powder, or a granular material, and lifts and conveys the workpiece, A suction unit having a suction surface that generates negative pressure to suction the surface of the workpiece; A connection portion connected to the workpiece transport device; A robot hand comprising: a floating mechanism disposed between the connection portion and the suction portion, which causes the suction surface of the suction portion to follow the surface of the workpiece. [Configuration 2] The floating mechanism includes: A first plate fixed to the connection portion; a second plate to which the adsorption portion is fixed and which faces the first plate; A shaft provided upright on the second plate; an elastic body disposed between the first plate and the second plate and applying an elastic force in a direction in which the first plate and the second plate are separated from each other; the first plate has a tapered hole that becomes smaller in diameter toward the second plate, A tapered portion having a tapered surface corresponding to the shape of the tapered hole is provided at a tip of the shaft, The robot hand of configuration 1, wherein the shaft is configured to be capable of being inserted and removed from the tapered hole and to be capable of swinging, and the tapered portion is configured to be accommodated in the tapered hole and to be capable of being engaged with the tapered hole. [Configuration 3] The outer diameter of the shaft is configured to be smaller than the diameter of the small diameter portion of the tapered hole, A robot hand as described in configuration 2, wherein the vertical length dimension of the tapered hole is longer than the vertical length dimension of the tapered portion, and the size of the large diameter portion of the tapered hole is larger than the size of the large diameter portion of the tapered portion. [Configuration 4] the elastic body is a coil spring attached to the outside of the shaft, and a spring receiving portion for the coil spring is provided at at least one end of the coil spring that is closer to the second plate, the spring receiving portion has a cylindrical portion through which the shaft is inserted and a flange portion provided on an outer periphery of the cylindrical portion, an end portion of the coil spring on the second plate side is attached to the outside of the cylindrical portion and is in pressure contact with the second plate via the flange portion; 4. The robot hand according to configuration 3, wherein the outer diameter of the cylindrical portion is larger than the diameter of the small diameter portion of the tapered hole. [Configuration 5] A spring receiving portion for the coil spring is provided at one end of each of the two ends of the coil spring that is closer to the first plate, an end portion of the coil spring on the first plate side is attached to the outside of the cylindrical portion of the spring receiving portion on the first plate side and abuts against the first plate via the flange portion of the spring receiving portion; 5. The robot hand according to configuration 4, wherein an inner diameter of the spring receiving portion on the first plate side is formed to be larger than a diameter of the shaft. [Configuration 6] The robot hand according to configuration 5, wherein the spring receiving portion on the first plate side is in slidable contact with the first plate. [Configuration 7] The robot hand according to any one of configurations 2 to 6, wherein three or more shafts are provided and are not arranged in a straight line. [Configuration 8] A robot hand described in any one of configurations 2 to 6, in which three shafts are provided, each of which is arranged so that the distance between each of the shafts is equal, and all of the shafts are arranged so as to fit within the surface area of ​​the workpiece. [Explanation of symbols]

[0099] 10...workpiece transport device, 20...hand portion, 24...connection portion, 25...suction pad, 25a...suction surface, 80...floating mechanism, 81...first plate, 81a-81c...tapered hole, 82...second plate, 83a-83c...shaft, 84...coil spring, 85...tapered portion, 86...spring support portion, 91...X-axis servo motor, 92...Y-axis servo motor, 93...Z-axis servo motor, 94...swivel axis servo motor, 95...ejector, 96...storage device, 97...workpiece transport program, 100...control device, W...workpiece.

Claims

1. A workpiece conveying device that adsorbs a workpiece, which is a bag containing a liquid, a powder, or a granular material, and lifts and conveys the workpiece, A robot hand and A first drive unit that moves the robot hand in a vertical direction; A second drive unit that moves or rotates the robot hand in a horizontal direction; a drive control unit that controls the first drive unit and the second drive unit, The robot hand includes: A suction unit having a suction surface that generates negative pressure to suction the surface of the workpiece; A connection portion connected to the workpiece transport device; a floating mechanism disposed between the connection portion and the suction portion and adapted to cause an adsorption surface of the suction portion to follow the surface of the workpiece; The drive control unit is A workpiece transport device that controls the second drive unit so as to set a free state in which no torque is generated in any horizontal direction for the robot hand when the first drive unit lowers the robot hand and abuts the suction surface against the surface of the workpiece.

2. the second driving unit includes at least one of an X-axis motor that moves the robot hand in a predetermined X-axis direction in a horizontal direction, a Y-axis motor that moves the robot hand in a Y-axis direction perpendicular to the X-axis direction in the horizontal direction, and a rotation axis motor that rotates the robot hand in the horizontal direction; 2. The workpiece transportation device according to claim 1, wherein the drive control unit sets the free state by cutting off current to at least one of the X-axis motor, the Y-axis motor, and the rotation axis motor when controlling the first drive unit to lower the robot hand and bring the suction surface into contact with the surface of the workpiece.

3. The drive control unit is setting at least one of the X-axis motor, the Y-axis motor, and the rotation axis motor to the free state after starting to lower the robot hand and before the suction surface is brought into contact with the surface of the workpiece; A workpiece transport device as described in claim 2, wherein after the suction portion suctions the workpiece, the robot hand starts to rise, and the free state is released by the time the rise is completed and the robot hand is moved or rotated in the horizontal direction.

4. The floating mechanism includes: A first plate fixed to the connection portion; a second plate to which the suction portion is fixed and which faces the first plate; a shaft provided upright on the second plate; an elastic body disposed between the first plate and the second plate and applying an elastic force in a direction in which the first plate and the second plate are separated from each other; The first plate has a tapered hole having a smaller diameter toward the second plate, A tapered portion having a tapered surface corresponding to the shape of the tapered hole is provided at a tip of the shaft, A workpiece transport device described in any one of claims 1 to 3, wherein the shaft is configured to be able to be inserted and removed from the tapered hole and to be able to swing, and the tapered portion is accommodated in the tapered hole and is configured to be able to be engaged with the tapered hole.

5. A workpiece conveying program for a workpiece conveying device that adsorbs a workpiece, which is a bag containing a liquid, a powder, or a granular material, and conveys the workpiece by lifting it up, The workpiece transport device is A robot hand and A first drive unit that moves the robot hand in a vertical direction; A second drive unit that moves or rotates the robot hand in a horizontal direction; a drive control unit that controls the first drive unit and the second drive unit, The robot hand includes: A suction unit having an adsorption surface that generates negative pressure to adsorb the surface of the workpiece; A connection portion connected to the workpiece transport device; a floating mechanism disposed between the connection portion and the suction portion and adapted to cause an adsorption surface of the suction portion to follow the surface of the workpiece; A workpiece transport program that causes the drive control unit to execute a free control step of controlling the second drive unit so as to set a free state in which no torque is generated in any horizontal direction for the robot hand when the first drive unit lowers the robot hand and brings the suction surface into contact with the surface of the workpiece.

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