Workpiece transfer device and workpiece transfer 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 transfer device and a workpiece transfer program.

Background Art

[0002] Conventionally, automation of depalletizing work (or palletizing work, the same applies hereinafter) for bag bodies and the like has been implemented by using palletizing robots and handling robots. As a robot hand used for automation of such depalletizing work, for example, one described in Patent Document 1 is known.

[0003] The robot hand described in Patent Document 1 is configured such that after a suction pad is brought into contact with a workpiece to be depalletized, a vacuum suction force is applied to the suction pad via a chamber connected thereto, whereby the workpiece is sucked and lifted by the suction pad, and conveyed in the lifted state.

[0004] By the way, workpieces such as bag bodies containing rice, grains and the like are deformable without a specific fixed shape. For this reason, when stacked on a pallet, the load may collapse such that it falls inward due to an error in the loading / unloading position during palletizing work (stacking work), vibration during transportation, or the like, or the load may spread outward and collapse. That is, there are cases where all workpieces are not stacked in an orderly manner. If the position of the robot hand cannot be controlled such that the suction pad abuts against the central portion of the workpiece, a portion deviated from the central portion of the workpiece W will be eccentrically sucked and lifted. If the magnitude of the moment generated in the workpiece due to the deviation exceeds the suction force of the suction pad on the workpiece, the workpiece may come off the suction pad and fall during the depalletizing operation.

[0005] Therefore, the robot hand described 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 that changes the suction position of the suction pad on the workpiece based on the moment detected by this moment detection means. As a result, the suction pad can reliably hold the workpiece at its center of gravity. [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 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, workpieces such as bags may not only shift position, but their top surfaces may not be horizontal. In other words, workpieces such as bags containing rice or grains may change shape due to the movement of their contents, and their top surfaces 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 be created because the top surface of the workpiece is sloped, reducing the suction force and sometimes preventing stable suction.

[0009] The present invention has been made in view of the above problems, and its objective is to provide a workpiece transfer device and a workpiece transfer program that can appropriately contact the suction part with the workpiece even when there is variation in the orientation of the workpiece. [Means for solving the problem]

[0010] A workpiece transfer device to solve the above problems is: A workpiece conveying device that adsorbs and lifts a workpiece, which is a bag containing a liquid, powder, or granular material, to transport the workpiece, Robot hand and A first drive unit that moves the robot hand in the vertical direction, A second drive unit that moves or rotates the robot hand in the horizontal direction, The system comprises a drive control unit that controls the first drive unit and the second drive unit, The aforementioned robot hand is An adsorption part having an adsorption surface that generates negative pressure to adsorb to the surface of the workpiece, A connection part connected to the workpiece transport device, The system includes a floating mechanism positioned between the connecting portion and the suction portion, which causes the suction surface of the suction portion to follow the surface of the workpiece, The drive control unit, 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 a free state in which no torque is generated in any direction horizontal to the robot hand.

[0011] This allows the suction part to properly contact the surface of the workpiece and achieve stable adhesion, even when there are variations in the workpiece's orientation.

[0012] A workpiece transport program to solve the above problem, A workpiece transport program for a workpiece transport device that adsorbs and lifts a workpiece, which is a bag containing a liquid, powder, or granular material, to transport the workpiece, The workpiece transport device is, Robot hand and A first drive unit that moves the robot hand in the vertical direction, A second drive unit that moves or rotates the robot hand in the horizontal direction, The system comprises a drive control unit that controls the first drive unit and the second drive unit, The aforementioned robot hand is a suction portion having a suction surface that generates negative pressure to suction the surface of the workpiece; a connection portion connected to the workpiece transfer device; 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, causing the drive control unit to execute a free control step of controlling the second drive unit to set a free state in which no torque is generated in any one of the horizontal directions relative to the robot hand, when the first drive unit lowers the robot hand to bring the suction surface into contact with the surface of the workpiece.

[0013] Thereby, even when there are variations in the posture of the workpiece, the suction portion can be properly brought into contact with the surface of the workpiece to stably suction the workpiece. [Brief Description of the Drawings]

[0014] [Figure 1] A perspective view of the workpiece transfer device. [Figure 2] A perspective view of the robot hand as viewed from above. [Figure 3] A perspective view of the robot hand as viewed from below. [Figure 4] A front view of the robot hand. [Figure 5] A side view of the robot hand. [Figure 6] A top view of the floating mechanism. [Figure 7] A cross-sectional view taken along line A-A of the floating mechanism. [Figure 8] A partial cross-sectional view showing the operation mode of the hand unit. [Figure 9] An enlarged cross-sectional view of the floating mechanism. [Figure 10] A partial cross-sectional view showing the operation mode of the hand unit. [Figure 11] A cross-sectional view of a floating mechanism according to a modified example. [Figure 12] A block diagram showing the configuration of a control device in the second embodiment. [Figure 13]Flowchart of the transport process in the second embodiment. [Figure 14] A partial cross-sectional view showing the operation of the hand portion in the second embodiment. [Figure 15] A partial cross-sectional view showing the operation of the hand portion in the second embodiment. [Modes for carrying out the invention]

[0015] The following describes embodiments of the "robot hand" according to the present invention with reference to the drawings. In the following embodiments and modifications, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the descriptions of such parts are provided accordingly. Furthermore, in the descriptions of embodiments and modifications, it is possible to combine embodiments and modifications not only in the combinations of configurations explicitly stated, but also in any other way, as long as there are no particular problems with the combination.

[0016] (First Embodiment) As shown in Figure 1, the workpiece transport device 10 is a device that sequentially transports workpieces W from the supply location and loads them onto a portable pallet P installed at a predetermined location, in other words, it is a device that performs palletizing. The workpiece transport device 10 is also a device that sequentially transports the workpieces W loaded onto the portable pallet P installed at a predetermined location to a predetermined discharge location, in other words, it is a device that performs depalletizing. In principle, when performing depalletizing, the reverse operation of palletizing is performed, so in this embodiment, palletizing will be mainly described.

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

[0018] The workpiece W is supplied from an external transport device (such as a belt conveyor) to a roller conveyor 1 installed in the workpiece transport device 10. The supplied workpiece W is then positioned and stopped at a predetermined stationary position by a stopper (not shown) installed on the roller conveyor 1. The workpiece transport device 10 is configured to detect the workpiece W that is positioned and stationary on the roller conveyor 1 using sensors or other means, and then lift and transport it.

[0019] When depalletizing is performed, the reverse operation of the palletizing described above is carried out. In other words, the workpiece W is lifted from the pallet P by the workpiece transport device 10 and discharged to external transport equipment via the roller conveyor 1 or the like.

[0020] Next, the configuration of the workpiece transfer device 10 will be described in detail. As shown in Figure 1, the workpiece transfer device 10 comprises a hand unit 20 as a robot hand for gripping the workpiece W, a transfer mechanism 30 for moving the hand unit 20, and a rectangular parallelepiped frame 70 to which the transfer mechanism 30 is fixed. The workpiece transfer device 10 also comprises a control device 100 for controlling the operation of the hand unit 20 and the transfer mechanism 30, and a controller (not shown) as an information terminal capable of inputting and outputting various types of information.

[0021] In this embodiment, the longitudinal direction of the frame 70 is defined as the X-axis direction, the transverse direction (perpendicular to the X-axis) as the Y-axis direction, and the direction perpendicular to the X-axis and Y-axis directions as the Z-axis direction. Since the workpiece transport device 10 is typically installed on a flat surface, the Z-axis direction corresponds to the vertical direction. The X-axis and Y-axis directions correspond to the horizontal direction.

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

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

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

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

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

[0027] As shown in Figure 1, the hand portion 20 is fixed to the arm portion 60 via a rotation mechanism 23 which acts as a pivoting mechanism. The rotation mechanism 23 is configured to allow the hand portion 20 to pivot around the Z-axis (in the direction of arrow R in Figure 1) based on the driving force of a built-in pivot axis servo motor 94.

[0028] As shown in Figures 2 and 3, the hand unit 20 has a connecting part 24 that is connected to and fixed to the rotating mechanism 23, a suction pad 25 that serves as a suction part, and a floating mechanism 80 that is positioned between the connecting part 24 and the suction pad 25. The suction pad 25 is positioned with its suction surface 25a facing downwards. The suction pad 25 is connected to an ejector via air piping (not shown). The operation of the ejector creates negative pressure inside the suction pad 25, which makes it possible to suction the upper surface of the workpiece W. The contact portion of the suction pad 25 is made of rubber or sponge and is configured to absorb surface irregularities on the workpiece W to some extent.

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

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

[0031] This control device 100 is connected to various sensors, various servo motors 91-94, and controllers, and is configured to acquire various information. Furthermore, the control device 100 has various functions and executes these functions based on the acquired information. These functions are realized by executing programs stored in the storage device (memory) of the control device 100. These functions may be realized by hardware electronic circuits, or at least part of them may be realized by software, i.e., by processing executed on a computer.

[0032] Among the various functions, there is, for example, a palletizing function that transports workpieces W and loads them onto a pallet P. Briefly explaining the palletizing function, the control device 100 detects the position of the workpieces W using sensors, lifts the workpieces W with the handle unit 20, moves the handle unit 20 together with the workpieces W onto the pallet P using the transport mechanism 30, and releases them to load the workpieces W. With this function, the workpieces W are stacked on the pallet P in multiple layers in the vertical direction (Z-axis direction). At that time, the workpieces may be stacked in a manner that aligns them into multiple rows in a predetermined direction (X-axis direction or Y-axis direction).

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

[0034] By the way, as mentioned above, the workpiece W in this embodiment is a bag containing rice, grains, etc. Therefore, although the workpiece W maintains a certain shape due to the bag, its shape changes due to the movement of its contents, and the top surface may be inclined with respect to the horizontal plane. In this case, with a conventional robot hand, even if the suction pad is pressed against the workpiece W so as to be perpendicular to the horizontal direction, a gap may be created because the top surface of the workpiece W is inclined, reducing the suction force and potentially preventing stable suction.

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

[0036] As shown in Figures 2 and 4, the floating mechanism 80 comprises a first plate 81 fixed to the connecting 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 provided vertically on the second plate 82, and a coil spring 84 as an elastic body positioned between the first plate 81 and the second plate 82 and applying an elastic force in the direction that separates them.

[0037] The first plate 81 is configured in a disc shape, as shown in Figure 6. As shown in Figures 2 and 4, the first plate 81 is positioned above the hand portion 20 in the vertical direction (Z-axis direction), and the connecting portion 24 is attached to its upper surface.

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

[0039] As shown in Figure 2 and other figures, the second plate 82 is configured in the shape of a long plate, positioned below the first plate 81 in the vertical direction, and facing the first plate 81 in the vertical direction. A suction pad 25 is fixed to the lower surface of the second plate 82, and shafts 83a to 83c are erected on the upper surface of the second plate 82.

[0040] As shown in Figures 2 and 6, there are three shafts 83a to 83c, positioned to correspond to the tapered holes 81a to 81c of the first plate 81. That is, the distance between the centers of the shafts 83a to 83c is equal and the same as the distance between the centers of the tapered holes 81a to 81c. In other words, the shafts 83a to 83c are positioned so that their central axes are located at the vertices of an equilateral triangle.

[0041] As shown in Figures 4 and 7, the shafts 83a to 83c are each formed in a rod shape and are fixed perpendicular to the upper surface of the second plate 82. In other words, when the second plate 82 is positioned opposite the first plate 81, the shafts 83a to 83c are shaped to extend from the second plate 82 towards 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] As shown in Figure 7, the tips of the shafts 83a to 83c, which are inserted into the tapered holes 81a to 81c, are provided with a substantially frustoconical tapered portion 85 having a tapered surface corresponding to the shape of the tapered holes 81a to 81c. This tapered portion 85 is housed inside the tapered holes 81a to 81c and is provided so as to be able to lock into the tapered holes 81a to 81c.

[0043] More specifically, the tapered portion 85 is formed so that its diameter decreases towards the second plate 82, that is, it increases in diameter as it moves away from the second plate 82. Furthermore, the outer diameter of the small-diameter portion (lower portion) of the tapered portion 85 is greater than or equal to 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. In addition, the outer diameter R2 of the large-diameter portion (upper portion) of the tapered portion 85 is formed to be at least larger than the diameter R3 of the small-diameter portion of the tapered holes 81a to 81c. Therefore, the tapered portion 85 is locked in place by the tapered holes 81a to 81c.

[0044] Furthermore, as mentioned above, since it has a tapered surface corresponding to the shape of the tapered holes 81a to 81c, the inclination angle α of the tapered surface of the tapered portion 85 is the same as the inclination angle α of the tapered surface 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 45 degrees. Therefore, as shown in Figure 7, when the direction of the shafts 83a to 83c is aligned with the vertical direction, the tapered portion 85 will be in surface contact with the tapered holes 81a to 81c. Consequently, when the tapered portion 85 is locked to the tapered holes 81a to 81c, it will be locked stably.

[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, it is about half the length. Also, 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. In other words, when the tapered portion 85 is locked against the tapered holes 81a to 81c, a gap (clearance) is provided above the tapered portion 85. Consequently, the shafts 83a to 83c are configured to move vertically relative to the first plate 81 and to be able to move in and out of the tapered holes 81a to 81c.

[0046] Furthermore, the diameter R1 of the shafts 83a to 83c is smaller than the diameter R3 of the smaller diameter portion of the tapered holes 81a to 81c, as shown in Figure 7. Specifically, the diameter R1 of the shafts 83a to 83c is about half the size of the diameter R3 of the smaller diameter portion of the tapered holes 81a to 81c. The tapered portion 85 attached to the tip of the shafts 83a to 83c is housed in tapered holes 81a to 81c, which become larger in diameter as they move away from the second plate 82.

[0047] From the above, when the tapered portion 85 is pushed towards the first plate 81 (opposite side from the second plate 82), the shafts 83a to 83c can move a predetermined distance horizontally. In addition, as shown in Figure 9, when the tapered portion 85 is pushed towards the first plate 81, the shafts 83a to 83c can tilt by a predetermined angle (shown as angle β in Figure 9). That is, when the tapered portion 85 is pushed towards the first plate 81, the shafts 83a to 83c are configured to swing relative to the first plate 81.

[0048] Next, the coil spring 84 will be described. As shown in Figures 2 and 7, the coil spring 84 is a compression coil spring positioned between the first plate 81 and the second plate 82, and applies an elastic force in the direction that separates them. The coil spring 84 is mounted on the outside of the shafts 83a to 83c. That is, the shafts 83a to 83c are positioned inside the coil spring 84.

[0049] As shown in Figure 7, a spring support portion 86 for the coil spring is provided at the end of the coil spring 84 that faces the second plate 82. The spring support portion 86 has a cylindrical portion 87 and a flange portion 88 provided on the outer circumference of the cylindrical portion 87. Shafts 83a to 83c are inserted through the inside of the cylindrical portion 87. The cylindrical portion 87 is designed to move along the shafts 83a to 83c. The end of the coil spring 84 that faces the second plate 82 is mounted on the outside of the cylindrical portion 87 and contacts (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 designed not to shift laterally (i.e., outward) relative to the cylindrical portion 87.

[0050] Furthermore, 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 of the coil spring 84 is not displaced laterally with respect to the cylindrical portion 87, the elastic force is applied in the direction in which the shafts 83a to 83c extend, that is, perpendicular to the second plate 82.

[0051] On the other hand, at least one end of the coil spring 84 on the side of the first plate 81 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 imparts an elastic force along the direction in which the shafts 83a to 83c extend, but as mentioned above, the shafts 83a to 83c can be tilted with respect to the first plate 81. As shown in Figures 8 and 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 the elastic force of the coil spring 84 also increases. 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.

[0052] Furthermore, the inner diameter of the coil spring 84 is formed to be larger than the diameter of the smaller portion of the tapered holes 81a to 81c. And, since the end of the coil spring 84 on the second plate 82 side does not shift laterally relative to the shafts 83a to 83c due to the spring receiving portion 86, the end of the coil spring 84 on the first plate 81 side also does not shift laterally much relative to the shafts 83a to 83c. For this reason, as shown in Figure 9, even if the shafts 83a to 83c are tilted relative to the first plate 81, the coil spring 84 is prevented from entering the tapered holes 81a to 81c.

[0053] Next, the operation of the floating mechanism 80 when lifting the workpiece W by the hand unit 20 will be explained with reference to Figures 8 to 10. It is assumed that the upper surface of the workpiece W to be transported is inclined with respect to the horizontal direction. Figures 8 to 10 show the floating mechanism 80 in cross-section. For the sake of explanation, the suction pad 25 is simplified in the illustration, and the connection part 24 is omitted from the illustration.

[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 horizontal suction surface 25a is pressed against the upper surface of the workpiece W, which is inclined with respect to the horizontal direction.

[0055] At this time, depending on the orientation of the workpiece W, some or all of the shafts 83a to 83c are pushed into the tapered holes 81a to 81c of the first plate 81, as shown in Figures 8 and 9. However, because the elastic force of the coil spring 84 exerts force in the direction that separates the first plate 81 and the second plate 82, even if some of the shafts 83a to 83c are pushed in, not all of the shafts 83a to 83c are pushed in in the same way. As a result, the shafts 83a to 83c are tilted relative to the first plate 81, and the second plate 82 is tilted. Consequently, the suction surface 25a of the suction pad 25 to which the second plate 82 is fixed is tilted 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 makes contact without any gaps.

[0056] After contact, the control device 100 generates negative pressure to attract the workpiece W with the suction pad 25. After attracting the workpiece W, the control device 100 moves the hand unit 20 upward. As shown in Figure 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 portion 85 is locked into the tapered holes 81a to 81c. Once the shafts 83a to 83c are pulled out and the tapered portion 85 is locked into the tapered holes 81a to 81c, the second plate 82 becomes horizontal, and the lifted workpiece W also becomes horizontal.

[0057] The control device 100 moves the hand portion 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 when the workpiece W is moved horizontally, vibration is suppressed and it is kept in a horizontal position. Therefore, it becomes possible to move it horizontally stably.

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

[0059] A floating mechanism 80 is provided between the connecting portion 24 and the suction pad 25, which causes the suction surface 25a of the suction pad 25 to follow the surface of the workpiece W. This allows the suction pad 25 to make proper contact with the surface of the workpiece W and to stably adhere to it, even if there are variations in the orientation of the workpiece W.

[0060] The shafts 83a to 83c are configured to be retractable and swingable within the tapered holes 81a to 81c, and are equipped with a coil spring 84 that applies elastic force in a direction that separates the first plate 81 and the second plate 82. As a result, when the hand portion 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. This allows the suction surface 25a of the suction pad 25 to be inclined according to the upper surface of the workpiece W. Since the elastic force of the coil spring 84 is exerted in a direction that separates the first plate 81 and the second plate 82, even if some of the shafts 83a to 83c are pushed in, not all of the shafts 83a to 83c will be pushed in the same way, and they can be appropriately inclined according to the upper surface of the workpiece W.

[0061] Furthermore, a tapered section 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 section 20 is moved upward after suction, the weight of the workpiece W and the elastic force of the coil spring 84 cause the tapered section 85 to lock into the tapered holes 81a to 81c, thereby allowing the second plate 82 and the workpiece W to be placed in a horizontal position. Therefore, the workpiece W can be moved horizontally in a stable state. Moreover, when the tapered section 85 is locked into the tapered holes 81a to 81c, surface contact is made, which suppresses vibration and maintains a stable state.

[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 of the large diameter portion (diameter R4) of the tapered holes 81a to 81c is made larger than the size of the large diameter portion (outer diameter R2) of the tapered portion 85. As a result, by pushing the shafts 83a to 83c into the tapered holes 81a to 81c, the tapered portion 85 can be moved into the gap within the tapered holes 81a to 81c. At this time, the tapered portion 85 can be moved horizontally within the range of the tapered holes 81a to 81c. As a result, the shafts 83a to 83c can be oscillated with respect to the first plate 81.

[0063] Furthermore, since the diameter R1 of the shafts 83a to 83c is smaller than the diameter R3 of the smaller diameter portion of the tapered holes 81a to 81c, there is more clearance before the shafts 83a to 83c come into contact with the tapered holes 81a to 81c, allowing for a larger tilting angle of the shafts 83a to 83c.

[0064] A spring receiving portion 86 for the coil spring is provided at the end of the coil spring 84 that is on the side of the second plate 82. The outer diameter of the cylindrical portion 87 of the coil spring 84 is made to be approximately 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 prevents the end of the coil spring 84 on the side of the first plate 81 from shifting laterally relative to the shafts 83a to 83c. Therefore, even if the shafts 83a to 83c are tilted 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. This makes it easy to tilt the second plate 82 in the direction of rotation along the X axis and the Y axis.

[0066] Three shafts 83a to 83c are provided, and they are arranged so that the spacing between each shaft 83a to 83c is equal. This allows for a larger inclination angle compared to when four or more shafts 83a to 83c are provided. Furthermore, all shafts 83a to 83c are arranged to fit within the surface area of ​​the workpiece W. This allows for a larger inclination angle while maintaining a compact size.

[0067] (modified version) The following describes modified examples in which a part of the floating mechanism 80 in the above embodiment has been changed.

[0068] In the above embodiment, as shown in Figure 11, a spring receiving portion 101 for the coil spring may be provided at the end of the coil spring 84 on the side of the first plate 81. Similar to the spring receiving portion 86, this spring receiving portion 101 has a cylindrical portion 102 and a flange portion 103 provided on the outer circumference of the cylindrical portion 102. Shafts 83a to 83c are inserted inside 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 side of the second plate 82. Furthermore, the inner diameter R10 of the cylindrical portion 102 is set to be sufficiently larger than the diameter R1 of the shafts 83a to 83c. For this reason, a gap is provided between the shafts 83a to 83c so that they can move laterally relative to the cylindrical portion 102.

[0069] Therefore, as shown in Figure 11(b), when the shafts 83a to 83c are pushed into the tapered holes 81a to 81c, the shafts 83a to 83c can be tilted relative 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] Furthermore, the outer diameter shape of the spring receiving portion 101 is almost the same as that of the spring receiving portion 86. As a result, the coil spring 84 exerts elastic force on the first plate 81 via the flange portion 103 of the spring receiving portion 101. In addition, since the outer diameter shape of the flange portion 103 is larger than the outer diameter of the small diameter portion of the tapered holes 81a to 81c, 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 contact with the first plate 81 in a manner that allows it to slide. In other words, the spring receiving portion 101 is configured to slide in the direction of arrow T in Figure 11. Therefore, when the shaft 83 is tilted, the spring receiving portion 101 slides, preventing it from interfering with the cylindrical portion 102 of the spring receiving portion 101, and allowing the tilt angle to be increased.

[0072] In the above embodiment, as shown in Figure 11, the inclination angle of the tapered surface in 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 modifies a part of the first embodiment described above, will now be described. In the second embodiment, the mechanical configuration of the workpiece transfer device 10 is the same as in the first embodiment, so the same reference numerals are used and their description is omitted. In the second embodiment, the processing content and control content of the control device 100 will be described in detail.

[0075] As shown in Figure 12, the control device 100 is connected to various servo motors 91-94 and an ejector 95. By performing drive control of the various servo motors 91-94, the control device 100 can move the hand unit 20 along the X-axis, Y-axis, or Z-axis, or rotate the hand unit 20 around the pivot 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 pivot 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 upper surface of the workpiece W to be attracted to the suction pad 25, and to release the suction. Although not shown in the diagram, the control device 100 is connected to various sensors and, based on the detection results from the various sensors, determines the position of the workpiece W and performs drive control of various servo motors 91 to 94 and operation control of the ejector 95.

[0077] Next, we will explain the processing performed by the control device 100 when the workpiece W is lifted by the hand unit 20. The control device 100 performs the transport process shown in Figure 13 by executing the workpiece transport program 97 stored in the storage device 96 provided in the control device 100. The transport process will be explained in detail below.

[0078] When the transport process is performed, the control device 100 confirms the position of the workpiece W to be transported from the detection results of various sensors and moves the hand unit 20 horizontally so that the hand unit 20 is positioned above the workpiece W (step S101). 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 coincide 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 coincide in the Y-axis direction. The control device 100 also drives and controls the swivel 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 the Z-axis servo motor 93 to lower the hand unit 20 toward the workpiece W (step S102). Then, when the suction surface 25a of the suction pad 25 comes into contact with the surface of the workpiece W, the control device 100 sets a servo-free state (free state) in which no torque is generated in any horizontal direction relative to the hand unit 20 (step S103). Specifically, the control device 100 sets the servo-free state in which no torque is generated 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 slewing axis servo motor 94 (rotating axis motor). Step S103 in this embodiment corresponds to the free control step.

[0080] The servo-free state is one in which the hand unit 20 (more specifically the part on the first plate 81 side) can be moved or rotated arbitrarily in the horizontal direction by an external force, without its horizontal movement or rotation being restricted by the torque of the servo motors 91, 92, and 94. Therefore, if no torque is generated, it is not necessarily required 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, can be any timing between the start of the hand unit 20's descent (i.e., the start of step S102) and before the suction surface 25a of the suction pad 25 comes into contact with the surface of the workpiece W. For example, the distance between the hand unit 20 and the workpiece W may be measured by a distance measuring sensor, and the servo-free state may be set when this distance is less than or equal to a predetermined distance. Alternatively, the servo-free state may be set after a predetermined time has elapsed since the start of descent. Alternatively, 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 to pick up the workpiece W after the suction surface 25a of the suction pad 25 has come into contact with the surface of the workpiece W (step S104). After picking up the workpiece W, the control device 100 controls the drive of the Z-axis servo motor 93 to raise the hand unit 20 that has picked up the workpiece W (step S105). After raising the hand unit 20 that has picked up the workpiece W, the control device 100 releases the servo-free state (step S106). The timing of releasing the servo-free state can be any timing from the time the hand unit 20 starts to rise after the workpiece has been picked up by the suction unit until the rise is complete and the hand unit 20 moves or rotates in the horizontal direction. For example, the servo-free state may be released after a predetermined time has elapsed since the start of the rise to prevent the hand unit 20 from moving or rotating in the horizontal direction.

[0083] After the lifting is complete, the control device 100 moves the hand unit 20 horizontally to a predetermined position (on the pallet P or 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 the suction, and completes the transport of the workpiece W (step S108). Then the transport process ends.

[0084] The effects of setting the servo-free state will be explained with reference to Figures 14 and 15. It should be assumed that the upper surface of the workpiece W to be transported, as shown in Figures 14 and 15, is more inclined than the upper surface of the workpiece W shown in Figure 8. Figures 14 and 15 show the floating mechanism 80 in cross-section. For the sake of explanation, the suction pad 25 is simplified in the illustration, and the connection part 24 is omitted.

[0085] After detecting the workpiece W, the control device 100 lowers the hand unit 20 and presses the suction surface 25a of the suction pad 25 against the workpiece W. At this time, depending on the orientation of the workpiece W, some or all of the shafts 83a to 83c are pushed into the tapered holes 81a to 81c of the first plate 81, as shown in Figure 14. Note that because the elastic force of the coil spring 84 is exerted in the direction that separates the first plate 81 and the second plate 82, even if some of the shafts 83a to 83c are pushed in, not all of the shafts 83a to 83c are pushed in in the same way.

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

[0087] In this first embodiment, the hand portion 20, more specifically the portion on the first plate 81 side, was restricted from horizontal movement and rotation by the torque of the servo motors 91, 92, and 94. As a result, the shafts 83a to 83c engaged with the tapered holes 81a to 81c, preventing further tilting.

[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 portion on the first plate 81 side moves horizontally due to interference with the tapered holes 81a to 81c or due to the elastic force of the coil spring 84, as shown by the arrow in Figure 15. This allows the shafts 83a to 83c to tilt further.

[0089] Consequently, the second plate 82 and the suction pad 25 fixed to it are also tilted further relative to the first plate 81. As a result, the suction surface 25a can be made to follow the tilt of the upper surface of the workpiece W more closely and make contact without any gaps.

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

[0091] The control device 100 lowers the hand unit 20 and brings the suction surface 25a into contact with the surface (upper surface) of the workpiece W, setting a servo-free state in which no torque is generated horizontally relative to the hand unit 20. This allows the tilt angle of the floating mechanism 80 to be increased. Therefore, the suction surface 25a can be made to follow the tilt of the upper surface of the workpiece W more closely and make contact without any gaps.

[0092] The control device 100 sets a servo-free state by interrupting 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 with simple and low-power control. Furthermore, since movement in the X-axis and Y-axis directions, as well as rotation, is permitted, the device can follow the orientation of the upper surface of the workpiece W regardless of its position.

[0093] The control device 100 sets the servo-free state before the suction surface 25a contacts the upper surface of the workpiece W. After the workpiece W is picked up by the suction pad 25, the servo-free state is released. As a result, when the shafts 83a to 83c tilt, the portion on the first plate 81 side can be reliably moved without being hindered by the torque of the servo motors 91, 92, and 94.

[0094] The shafts 83a to 83c are configured to be retractable and pivotable within the tapered holes 81a to 81c, and are equipped with a coil spring 84 that applies an elastic force in the direction that separates the first plate 81 and the second plate 82. 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, making it easy to incline the shafts 83a to 83c.

[0095] Furthermore, 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, tilting does not consume power, and no special control is required.

[0096] Furthermore, the transport process by the control device 100 and the workpiece transport program 97 described in the second embodiment may be applied in combination with the first embodiment or its modified form.

[0097] In the second embodiment described above, a servo-free state was set for all of the X-axis servo motor 91, Y-axis servo motor 92, and slewing axis servo motor 94. However, it is also possible to set a servo-free state for only one of them. That is, a servo-free state may be set in which no torque is generated in any of the horizontal directions.

[0098] The following provides additional information on the technical ideas that can be derived from the above embodiments and modifications. [Configuration 1] A robotic hand used in a workpiece transport device that adsorbs and lifts a workpiece, which is a bag containing a liquid, powder, or granular material, to transport the workpiece, An adsorption part having an adsorption surface that generates negative pressure to adsorb to the surface of the workpiece, A connection part connected to the workpiece transport device, A robot hand comprising a floating mechanism disposed between the connecting 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 is, A first plate fixed to the aforementioned connection part, The adsorption portion is fixed to a second plate facing the first plate, The shaft is mounted upright on the second plate, The system comprises an elastic body positioned between the first plate and the second plate, which applies an elastic force in the direction that separates them, The first plate is provided with tapered holes that become smaller in diameter towards the second plate. The tip of the shaft is provided with a tapered portion having a tapered surface corresponding to the shape of the tapered hole. The robot hand according to configuration 1, wherein the shaft is configured to be retractable into and out of the tapered hole and to be pivotable, and the tapered portion is configured to be housed in the tapered hole and to be locked to the tapered hole. [Configuration 3] The outer diameter of the shaft is configured to be smaller than the diameter of the smaller diameter portion of the tapered hole. The robot hand according to configuration 2, wherein the vertical length of the tapered hole is longer than the vertical length 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. [Structure 4] The elastic body is a coil spring mounted on the outside of the shaft, and at least one end of the coil spring on the second plate side is provided with a spring support portion for the coil spring. The spring receiving portion has a cylindrical portion through which the shaft is inserted and a flange portion provided on the outer circumference of the cylindrical portion. The end of the coil spring on the second plate side is attached to the outside of the cylindrical portion and pressed against the second plate via the flange portion. The robot hand according to configuration 3, wherein the outer diameter of the cylindrical portion is formed to be larger than the diameter of the small-diameter portion of the tapered hole. [Composition 5] A spring support portion for the coil spring is provided at the end of the coil spring on the side of the first plate. The end 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 contacts the first plate via the flange portion of the spring receiving portion. The robot hand according to configuration 4, wherein the inner diameter of the spring receiving portion on the first plate side is formed to be larger than the diameter of the shaft. [Composition 6] The robot hand according to configuration 5, wherein the spring receiving portion on the first plate side is in contact with the first plate in a manner that allows for sliding movement. [Composition 7] The robot hand is provided with three or more shafts, and these shafts are not arranged in a straight line, as described in any of configurations 2 to 6. [Structure 8] The robot hand according to any one of configurations 2 to 6, wherein three shafts are provided, and the distances between each of the shafts are equal, and all of the shafts are arranged so that they are contained within the surface area of ​​the workpiece. [Explanation of Symbols]

[0099] 10...Workpiece transfer device, 20...Hand unit, 24...Connection unit, 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 section, 86...Spring support section, 91...X-axis servo motor, 92...Y-axis servo motor, 93...Z-axis servo motor, 94...Swivel axis servo motor, 95...Ejector, 96...Memory device, 97...Workpiece transfer program, 100...Control device, W...Workpiece.

Claims

1. A workpiece conveying device that adsorbs and lifts a workpiece, which is a bag containing a liquid, powder, or granular material, to transport the workpiece, Robot hand and A first drive unit that moves the robot hand in the vertical direction, A second drive unit that moves or rotates the robot hand in the horizontal direction, The system comprises a drive control unit that controls the first drive unit and the second drive unit, The aforementioned robot hand is An adsorption part having an adsorption surface that generates negative pressure to adsorb to the surface of the workpiece, A connection part connected to the workpiece transport device, The device comprises a floating mechanism positioned between the connecting portion and the suction portion, which allows vertical and horizontal displacement of the suction surface of the suction portion, thereby causing the suction surface of the suction portion to follow the surface of the workpiece. The drive control unit, A workpiece transfer device that, when the first drive unit lowers the robot hand and brings the suction surface into contact with the surface of the workpiece, and the floating mechanism causes the suction surface of the suction part to follow the surface of the workpiece, controls the second drive unit to a free state in which it does not generate torque in any of the horizontal directions, thereby allowing horizontal movement of the entire robot hand and allowing the suction surface to be displaced horizontally beyond the range that can be displaced by the floating mechanism alone.

2. The second drive unit comprises at least one of the following: an X-axis motor for moving the robot hand in a predetermined X-axis direction in the horizontal direction; a Y-axis motor for moving the robot hand in a Y-axis direction perpendicular to the X-axis direction in the horizontal direction; and a rotary axis motor for rotating the robot hand in the horizontal direction. The workpiece transfer device according to claim 1, wherein the drive control unit controls the first drive unit to lower the robot hand and bring the suction surface into contact with the surface of the workpiece, and sets the free state by interrupting the current to at least one of the X-axis motor, the Y-axis motor, and the rotary axis motor.

3. The drive control unit, From the time the robot hand starts descending until before the suction surface comes into contact with the surface of the workpiece, at least one of the X-axis motor, the Y-axis motor, and the rotary axis motor is set to the free state. The workpiece transfer device according to claim 2, wherein, after the workpiece is picked up by the suction part, the robot hand is started to rise, and the free state is released when the rise is completed and the robot hand is moved or rotated in the horizontal direction.

4. The floating mechanism is, A first plate fixed to the aforementioned connection part, The adsorption portion is fixed to a second plate facing the first plate, The shaft is mounted upright on the second plate, The system comprises an elastic body positioned between the first plate and the second plate, which applies an elastic force in a direction that separates them, The first plate is provided with tapered holes that become smaller in diameter towards the second plate. The tip of the shaft is provided with a tapered portion having a tapered surface corresponding to the shape of the tapered hole. The workpiece transport device according to any one of claims 1 to 3, wherein the shaft is configured to be retractable into and out of the tapered hole and to be pivotable, and the tapered portion is configured to be housed in the tapered hole and to be locked to the tapered hole.

5. A workpiece transport program for a workpiece transport device that adsorbs and lifts a workpiece, which is a bag containing a liquid, powder, or granular material, to transport the workpiece, The workpiece transport device is, Robot hand and A first drive unit that moves the robot hand in the vertical direction, A second drive unit that moves or rotates the robot hand in the horizontal direction, The system comprises a drive control unit that controls the first drive unit and the second drive unit, The aforementioned robot hand is An adsorption part having an adsorption surface that generates negative pressure to adsorb to the surface of the workpiece, A connection part connected to the workpiece transport device, The device comprises a floating mechanism positioned between the connecting portion and the suction portion, which allows vertical and horizontal displacement of the suction surface of the suction portion, thereby causing the suction surface of the suction portion to follow the surface of the workpiece. A workpiece transport program that causes the drive control unit to perform a free control step, which allows the entire robot hand to move horizontally, thereby allowing the suction surface to be displaced horizontally beyond the range that can be displaced by the floating mechanism alone, while the first drive unit lowers the robot hand, brings the suction surface into contact with the surface of the workpiece, and the floating mechanism causes the suction surface of the suction part to follow the surface of the workpiece, by controlling the second drive unit to a free state in which no torque is generated in any horizontal direction.

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