JP2008024493A - Article transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an article transfer device capable of accurately gripping an article over a long period, by preventing excessive gripping force from acting on the gripping article. <P>SOLUTION: This article transfer device has a mast movably erected in the substantially horizontal direction, a lifting stage 6 liftably supported along the mast, a lifting device for lifting the lifting stage 6, and a pair of forks 10 arranged on the lifting stage 6, freely expandable in the opposite direction to a rack of juxtaposed storages and gripping the article W by moving in the horizontal direction orthogonal to the opposed direction, and is provided with a control means 14 controlling the gripping force for gripping the article W, by controlling a current value of a first electric motor 11d for horizontally moving the pair of forks 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an article transfer apparatus that transports articles in, for example, an automatic warehouse and loads and unloads articles with a rack that stores the articles.

  Conventionally, in an automatic warehouse where unmanned items are stored and unloaded by computer control, for example, a plurality of racks for storing items, which are made of steel frames, are arranged in parallel in the horizontal direction and the vertical direction, and the items are transported. Some racks have a stacker crane (article transfer device) for loading and unloading articles. A stacker crane provided in this type of automatic warehouse generally has a traveling cart for traveling on rails extending to the floor and ceiling along the hangar, a mast connected to the traveling cart, and a vertical mast. A lifting platform that moves up and down along the mast and a lifting device that lifts and lowers the lifting platform are provided. In addition, the lifting platform is provided with a pair of forks that can be moved horizontally so as to change the distance between them, and that can extend and contract in a direction facing the rack. In this stacker crane, when the elevator platform moves up and down while traveling along the hangar and the elevator platform is placed at a position facing a predetermined rack, the pair of forks expands and contracts, and the articles gripped by the pair of forks Warehousing to be transferred from the lifting platform to the rack side and unloading to grip the articles in the rack and transfer them from the rack to the lifting platform side are performed.

  Further, a pair of forks provided in this type of stacker crane includes a fixed fork supported by a lifting platform so as to be horizontally movable, and a plurality of movable forks supported by the fixed forks and slidably engaged. (For example, refer to Patent Document 1). Then, the pair of forks move horizontally by driving the first motor, and can grip an article placed between the pair of forks, release the gripped state, and drive the second motor. By doing so, the movable fork slides and the pair of forks expand and contract, and the gripped article can be conveyed between the rack and the lifting platform. In addition, by providing the first motor with a torque limiter, when the pair of forks move horizontally to grip the article, it prevents the gripping force from acting more than necessary and prevents the article from being damaged. ing.

On the other hand, in such a stacker crane, a position detecting means is provided on a lifting platform. This position detection means detects the bottom plate surface of the rack (the surface on which the article is placed) when the elevator is raised and lowered, and when the article is received, the bottom surface of the article (the load receiving surface of the elevator) is placed on the rack. The lifting platform is stopped in a state of being slightly above the surface. This prevents the lower end side of the article from coming into contact with the bottom plate of the rack and damaging the article gripped by the pair of forks. In addition, when the article stored in the rack is taken out, the lifting platform is stopped at the same position as when the goods are received by the laser type detection sensor, and the pair of forks are horizontally moved and expanded and contracted to grasp the article in the rack. The bottom surface of the article is separated from the mounting surface of the rack by slightly raising the lifting platform.
JP 2003-206004 A

  However, in the article transfer device (stacker crane) provided with the torque limiter in the first motor, the drive of the first motor is controlled by the operation of the mechanical torque limiter for each gripping operation for gripping the article. For example, when the gripping operation is repeatedly performed several tens of thousands of times per day, the torque limiter reaches the end of its life early, or the accuracy of the gripper is distorted as the gripping operation is repeated. There is a possibility that the torque limiter may be operated in a state where the gripper is gripped by force or a sufficient gripping force is not applied to the article.

  In the article transfer device, when the article is delivered, the pair of forks slightly raise the elevator when the article in the rack is gripped. However, there is a problem that the conveyance efficiency is lowered due to the complexity.

  In view of the above circumstances, an object of the present invention is to provide an article transfer device that can prevent an excessive gripping force from acting on an article to be gripped and can accurately grip an article over a long period of time.

  In order to achieve the above object, the present invention provides the following means.

  The article transfer apparatus according to the present invention includes a mast that is erected so as to be movable in a substantially horizontal direction, an elevator that is supported to be movable up and down along the mast, an elevator that raises and lowers the elevator, and the elevator In the article transfer apparatus, comprising: a pair of forks that are provided on the table and are extendable in a direction opposite to a rack of the hangar arranged side by side, and move in a horizontal direction perpendicular to the opposite direction to grip the article. Control means is provided for controlling a gripping force for gripping the article by controlling a current value of a first electric motor for horizontally moving the pair of forks.

  In the article transfer device according to the present invention, the pair of forks includes a grip portion having a relative coefficient of friction with respect to the article larger than that of the other portion on an inner surface of the at least one fork that holds the article. It is more desirable.

  According to the article transfer device of the present invention, the control means for controlling the current value of the first motor to control the driving of the first motor is provided, so that the driving of the first motor and the movement of the pair of forks are performed. As a result, the gripping force acting on the article can be electrically controlled, so that the gripping operation is repeated as in the case of a mechanical torque limiter, so that the life is not shortened and the accuracy is not distorted. As a result, the drive of the first electric motor can be controlled with high accuracy at all times, and an excessive gripping force can be reliably prevented from acting on the article.

  In the article transfer device of the present invention, the inner surface for holding the article of the pair of forks is provided with a grip portion having a relative coefficient of friction relative to the article as compared with the other parts, thereby reducing the article. The gripping force can be reliably gripped, and the article can be more reliably prevented from being damaged.

  Furthermore, by providing the gripping portion only on the inner surface of one of the forks, the side surface of the article gripped by the pair of forks intersects the inner surface of the pair of forks, Even when the article is tilted, the part where the gripping part of one fork of the tilted article is in contact with the frictional force and the other fork is in contact Can be slid along the other fork, and the position of the article can be corrected according to the gripping operation of the pair of forks. As a result, it is possible to reliably and stably hold an article placed in a tilted state.

  In addition, by providing the grip portion on the fork in this way, the gripping force controlled so that the article can be suitably gripped by controlling the current value of the first electric motor by the control means can be applied to the article reliably and accurately. Can do. As a result, the article can be gripped more reliably and stably.

  Hereinafter, an article transfer apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 to 8. This embodiment relates to, for example, a stacker crane (article transfer device) that transports articles in an automatic warehouse.

  In the automatic warehouse A of the present embodiment, as shown in FIG. 1, a plurality of racks 1a made of, for example, steel frames for storing articles W are arranged in parallel in the horizontal direction (arrow X direction) and the vertical direction (arrow Z direction). And a stacker crane 2 for loading and unloading articles W with respect to each rack 1a of the hangar 1.

  As shown in FIGS. 1 and 2, the stacker crane 2 of the present embodiment is provided on a floor surface and is movably provided on two floor guide rails 3 that extend in parallel along the hangar 1. The traveling cart unit 4, the guide frame 5 connected to the traveling cart unit 4 and having a substantially rectangular frame shape in a front view standing upright, and the lifting platform supported to be movable up and down inside the guide frame 5 6 and an elevating device 7 that is integrally attached to the guide frame 5 and raises and lowers the elevating platform 6 are main components.

  The guide frame 5 includes a pair of masts 5a that are vertically arranged, an upper frame member 5b that extends in a horizontal direction so as to connect the upper ends of the pair of masts 5a, a lower end of the pair of masts 5a, and a traveling carriage unit. 4, and a lower frame member 5 c connected to 4. Further, the guide frame 5 is formed in a substantially rectangular frame shape with a pair of masts 5a formed longer than the upper frame member 5b and the lower frame member 5c.

  As shown in FIG. 2, the traveling carriage unit 4 is composed of a pair of traveling mechanisms 4d and 4g. One traveling mechanism 4d rotates two rotating wheels 4b connected to each other by a rotating shaft 4a and the rotating shaft 4a. For example, a drive means 4c such as a servo motor is provided on one mast 5a side. The other traveling mechanism 4g includes two wheels 4f connected to each other by a rotation shaft 4e and is provided on the other mast 5a side. The traveling carriage unit 4 is configured such that one wheel 4b, 4f of each traveling mechanism 4d, 4g is disposed on each of the two floor guide rails 3, and can travel on the floor guide rail 3. Yes.

  As shown in FIG. 2, the lifting platform 6 is provided inside the guide frame 5 so as to be movable up and down along a pair of masts 5 a. The lifting platform 6 includes a cage frame 6a provided on both surfaces facing the inside of the pair of masts 5a and engaged with both ends in the horizontal direction (left and right direction), and a cage frame 6a supported by the cage frame 6a. A plurality of substantially rectangular flat plate-shaped load receiving bases 6b provided on the top are the main components. In addition, the plurality of cargo receiving platforms 6b form a cargo receiving surface S1 on which the upper surface is arranged on substantially the same horizontal plane and the article W is placed. Further, the lift 6 is provided with position detecting means 9 such as a laser detection sensor on the side surface of the cage frame 6a facing the rack 1a of the storage 1 shown in FIG. Further, as shown in FIGS. 2 to 4, a pair of forks 10 that can expand and contract in the facing direction with respect to the rack 1 a and can move in the horizontal direction perpendicular to the facing direction are provided above the load receiving platform 6 b. The cage frames 6a are respectively supported in parallel.

  As shown in FIGS. 2 to 5, each of the pair of forks 10 has a substantially rectangular plate-like fixed fork 10 a having a substantially U-shaped cross section, and a substantially rectangular plate shape that is engaged in parallel with each other and has a substantially U-shaped cross-section. The two movable forks (intermediate movable fork 10b, tip movable fork 10c) are configured. Of the two movable forks, the intermediate movable fork 10b is slidably engaged with the fixed fork 10a facing each other opening side, and the tip movable fork 10c is intermediately movable between the fixed fork 10a. With the fork 10b disposed, the intermediate movable fork 10b is slidably engaged.

  More specifically, as shown in FIG. 5, the pair of forks 10 are each provided with a pair of slide members 10d protruding upward and downward on the outer sides of the upper and lower ends of the fixed fork 10a. The intermediate movable fork 10b is formed with first guide grooves 10e that are opened inward and recessed outward, and second guide grooves 10f that are opened outward and recessed inward, at the upper and lower ends, respectively. Then, the pair of slide members 10d are engaged with the pair of first guide grooves 10e facing each other, so that the intermediate movable fork 10b is slidable along the fixed fork 10a. Moreover, the slide member 10g which protrudes inside is attached to the front-end | tip movable fork 10c inside the upper-lower end part, respectively. The pair of slide members 10g are engaged with the pair of second guide grooves 10f, respectively, so that the tip movable fork 10c is slidable along the intermediate movable fork 10b.

  Moreover, as shown in FIG.3 and FIG.4, the horizontal moving mechanism 11 which horizontally moves a pair of forks 10 to the longitudinal direction of the load receiving stand 6b is attached to a pair of forks 10. FIG. The horizontal movement mechanism 11 includes an endless and annular chain belt 11b connected to each fixed fork 10a via a connecting member 11a, a pair of sprockets 11c that rotatably supports the chain belt 11b, and one sprocket. For example, a first electric motor 11d such as a servo motor that rotates the 11c forward and backward is configured. Here, the connecting member 11a that connects each fixed fork 10a and the chain belt 11b is a portion of the chain belt 11b that is located above the connecting member 11a that is connected to one of the fixed forks 10a and is wound around the pair of sprockets 11c. The connecting member 11a connected to the other fixed fork 10a is connected to the chain belt 11b in the lower part. In the horizontal movement mechanism 11 configured as described above, the chain belt 11b rotates forward and backward by driving the first electric motor 11d, and the connecting members 11a and the fixed forks 10a move horizontally according to the rotation of the chain belt 11b. Thus, the pair of forks 10 can be brought close to or separated from each other.

  On the other hand, as shown in FIG. 3, the pair of forks 10 is provided with an expansion / contraction moving mechanism 12 for slidingly moving the intermediate movable fork 10b and the tip movable fork 10c. The expansion / contraction moving mechanism 12 is an endless type that is wound from outside and meshed with a spline shaft 12a extending in the left-right direction below the load receiving platform 6b and a sprocket (not shown) attached approximately at the center in the axial direction of the spline shaft 12a. A first transmission chain belt 12b having a shape, a first sprocket 12c meshed with a side of the first transmission chain belt 12b facing the spline shaft 12a, a second electric motor 12d having a rotation shaft connected to the first sprocket 12c, A second sprocket 12e in which the spline shafts 12a are coaxially arranged and are engaged with each other, a third sprocket 12f rotatably supported substantially at the center of the fixed fork 10a, a second sprocket 12e, and a second sprocket 12e. An endless second transmission chain belt 12g wound around a three-sprocket 12f; As shown in FIG. 5, a pinion 12h provided coaxially with the third sprocket 12f in a space defined by the fixed fork 10a and the intermediate movable fork 10b, and a pinion 12h fixed to the intermediate movable fork 10b, The engaged rack 12i, the fourth sprocket 12j provided on the front end side of the intermediate movable fork 10b, the fifth sprocket 12k provided on the rear end side of the intermediate movable fork 10b, as shown in FIG. A third transmission chain belt 12m fixed to the front end side of the fixed fork 10a and the other end fixed to the front end side of the front end movable fork 10c via the fifth sprocket 12k, and one end of the fixed fork 10a on the rear end side The fourth transmission chain is fixed to the rear end of the movable tip fork 10c via the fourth sprocket 12j. It is composed of a belt 12n. The second sprocket 12e shown in FIG. 3 has a spline shaft in which a spline having teeth on the inner periphery and a sprocket having teeth on the outer periphery are coaxially arranged and overlapped with each other. 12a meshes with the teeth on the inner periphery while being inserted into the communicating inner hole. The second electric chain belt 12g is wound while meshing with a sprocket having teeth on the outer periphery.

  In the telescopic movement mechanism 12, when the second electric motor 12d is driven, the first transmission chain belt 12b and the spline shaft (not shown) attached to the spline shaft 12a are wound around the first transmission chain belt 12b. 12a rotates around the axis, for example, in the positive direction. And while the 2nd sprocket 12e rotates, the 3rd sprocket 12f rotates via the 2nd power transmission chain belt 12g. The rotation of the third sprocket 12f rotates the pinion 12h, and the intermediate movable fork 10b slides and moves so as to extend the pair of forks 10 with respect to the fixed fork 10a via the rack 12i. At this time, the other end of the fourth transmission chain belt 12n is pulled toward the fourth sprocket 12j, and the tip movable fork 10c with the other end fastened is slid to extend outward from the fixed fork 10a. Thereby, a pair of forks 10 can be extended. On the contrary, when the spline shaft 12a is rotated in the reverse direction, the intermediate movable fork 10b slides so as to contract the pair of forks 10 via the rack 12i, and accordingly, the third transmission chain belt 12m. The other end is pulled toward the fifth sprocket 12k, and the tip movable fork 10c with the other end secured is pulled toward the fixed fork 10a. Thereby, a pair of forks 10 can be shrunk.

  Moreover, in this embodiment, as shown in FIG.3 and FIG.4, the electric current value sensor 13 which detects the electric current value of the 1st electric motor 11d is provided in connection with the 1st electric motor 11d. Further, a control means 14 is provided which is connected to the current value sensor 13 and the first electric motor 11d, and controls the current value of the first electric motor 11d while detecting the electric current value of the first electric motor 11d.

  Furthermore, each of the tip movable forks 10c of the pair of forks 10 has a gripping member such as foaming rubber, which extends in the longitudinal direction of the tip movable fork 10c and is parallel to the vertical direction on surfaces facing each other and facing inward. A (gripping part) 15 is provided. The gripping portion 15 has a larger relative friction coefficient with respect to the article W than other portions of the tip movable fork 10c.

  On the other hand, as shown in FIG. 2, the lifting device 7 includes a wire drum 7a provided on the upper end side of one mast 5a, a lifting motor 7b for rotating the wire drum 7a forward and backward, and an upper end of the other mast 5a. One end is wound around the sheave 7c provided on the side and the wire drum 7a, and the other end fed out from the wire drum 7a is connected to the cage frame 6a of the portion located on the one mast 5a side from above. One end side is wound around the first elevating wire 7d and the wire drum 7a, and the other end side fed out from the wire drum 7a is above the cage frame 6a of the portion located on the other mast 5a side via the sheave 7c. The second elevating wire 7e is connected to the second elevating wire 7e. Thus, the cage frame 6a (elevating platform 6) is supported in a suspended state by the two elevating wires 7d and 7e. For example, when the wire drum 7a rotates in the forward direction, both elevating wires 7d, 7e is wound around the wire drum 7a to raise the cage frame 6a. When the wire drum 7a is rotated in the reverse direction, both lifting wires 7d and 7e wound around the wire drum 7a are The cage frame 6a can be lowered by being sent out.

  The lifting device 7 receives the result of detecting the upper surface (mounting surface S2) of the bottom plate on which the article W of the predetermined rack 1a is detected by the position detecting means 9 of the cage frame 6a. Control means 16 for controlling driving is connected.

  Next, the operation and effect of the stacker crane 2 having the above configuration will be described.

  First, the pair of forks 10 is extended so that the article W conveyed by, for example, a belt conveyor arranged in parallel with the stacker crane 2 is positioned between the pair of forks 10 in a state where the lifting platform 6 is positioned at the lowermost position. . Then, as shown in FIG. 4, by driving the first electric motor 11 d of the horizontal movement mechanism 11, the pair of forks 10 is moved horizontally to the article W side, and the gripping portion 15 of the tip movable fork 10 c is moved to the side surface of the article W. To hold it in contact.

  At this time, the current value of the first motor 11d is detected by the current value sensor 13, and the detection result is sent to the control means 14, and the control means 14 determines the current of the first motor 11d based on the magnitude of the current value. The drive is controlled. 7A shows a pair of forks 10 during a gripping operation for gripping the article W, when transporting the gripped article W, and during a releasing operation for releasing the gripping state of the transported article W. The relationship between the horizontal movement speed of the fork 10 and time is shown. FIG. 7B shows the relationship between the current value of the first electric motor 11d and the time during the gripping operation, the transporting operation, and the opening operation. In FIG. 7A, the vertical axis indicates the moving speed of the pair of forks 10, with the time axis on the horizontal axis serving as a boundary so that the pair of forks 10 narrow the distance between each other on the vertical axis. The movement speed at the time of movement is shown, and the lower part of the vertical axis shows the movement speed at the time when the pair of forks 10 move so as to increase the distance between each other. In FIG. 7B, the vertical axis indicates the current value, the vertical axis indicates the current value during powering of the first electric motor 11d with the horizontal axis as the boundary, and the vertical axis indicates the regeneration. The current value at the time is shown.

  In the present embodiment, as shown in FIGS. 7A and 7B, at the time of the gripping operation, first, the control means 14 uses the torque necessary for accelerating the moving speed of the pair of forks 10. The current value is controlled to I1 so as to drive the first electric motor 11d. As a result, the pair of forks 10 approaches the article W while gradually increasing its moving speed. Next, when the moving speed of the pair of forks 10 reaches the preset maximum speed V1 (time T1), the control means 14 uses the encoder connected to the speed sensor that detects the moving speed of the pair of forks 10 for example to reach the maximum speed. While detecting that V1 has been reached, the current value is lowered to I2 so as to maintain this moving speed V1. Thereby, the torque of the first electric motor 11d decreases, and the pair of forks 10 approaches the article W at a constant speed V1. Next, since the size of the article W is known in advance, at the stage (time T2) when the pair of forks 10 moving at a constant speed V1 approaches the article W to a predetermined distance (time T2), the control means 14 controls the first electric motor 11d. Is switched to I3, which is in a regenerative state. As a result, the pair of forks 10 approaches the article W while gradually decreasing the moving speed.

  Then, when the pair of forks 10 comes into contact with the side surfaces of the article W at a slow moving speed V2 (time T3), the article W is sandwiched between the pair of forks 10 to stop the movement of the pair of forks 10. The rotation amount of the first electric motor 11d does not change. At the same time, the control means 14 switches the current value of the first electric motor 11d from the current value I3 in the regenerative state to the current value I4 in the power running state. Here, the current value I4 switched in this way is a predetermined current value set in advance, and the article W is not damaged by the torque of the first electric motor 11d driven by the current value I4. A predetermined gripping force that can be reliably gripped acts.

  Therefore, at the time of the above gripping operation, the control unit 14 controls the current value of the first electric motor 11d so that the moving speed of the pair of forks 10 and the gripping force acting on the article W are electrically controlled. Even when this kind of gripping operation is performed tens of thousands of times, the life is not shortened as in the case of the conventional mechanical torque limiter, and the control accuracy is not changed as the control is repeated. The article W can be gripped reliably and stably. In the present embodiment, the gripping portion 15 of the tip movable fork 10c has a large relative friction coefficient with respect to the article W, and the gripping portion 15 is configured to contact and grip the article W. By setting the current value I4 so that a small gripping force commensurate with the relative friction coefficient is applied to the article W, the article W can be held with a smaller gripping force than that of a conventional fork.

  Next, the pair of forks 10 that have gripped the article W on the transport device are shrunk so as to return to the original position by driving the second electric motor 12 d of the telescopic movement mechanism 12, so that the article W is received by the load receiving platform of the lifting platform 6. It is transferred (conveyed) onto 6b (on the receiving surface S1). Then, when the article W is conveyed onto the load receiving platform 6b, the stacker crane 2 is driven in the horizontal direction on the floor guide rail 3 toward the predetermined rack 1a for storing the article W by driving the traveling carriage unit 4. Move to. Simultaneously with the horizontal movement of the stacker crane 2, the wire drum 7a winds up the lifting wires 7d and 7e by driving the lifting motor 7b. As a result, the lifting platform 6 supported in a suspended state by the lifting wires 7d and 7e of the lifting device 7 rises along the pair of masts 5a, and reaches the height position of the predetermined rack 1a for storing the articles W. The elevator 6 and the article W are raised.

  In addition, even when the article W gripped by the pair of forks 10 is transferred from the transfer device onto the load receiving platform 6b or when the stacker crane 2 and the lifting platform 6 move the article W, FIG. ) And FIG. 7B, the current value of the first electric motor 11d is maintained at I4 by the control means 14. For this reason, the article W being conveyed is held by the pair of forks 10 with a suitable gripping force. Further, since the current value of the first electric motor 11d is continuously detected by the current value sensor 13, even if the current value changes during the conveyance, the change of the current value is captured and the control means 14 controls the current value so that the predetermined current value I4 is immediately maintained. Thus, the article W is reliably held and transported with a suitable gripping force.

  On the other hand, when approaching the predetermined rack 1a for storing the article W, as shown in FIG. 8A, the horizontal position of the placement surface S2 of the rack 1a is set by the position detecting means 9 provided on the cage frame 6a. Detected. The control means 16 connected to the lifting device 7 that has received the detection result controls the lifting device 7 so that the load receiving surface S1 of the lifting platform 6 is positioned above the placement surface S2 of the rack 1a. Stop rising. Thus, when the lifting platform 6 is stopped, the pair of forks 10 extends toward the inside of the rack 1a (outward in the direction facing the rack 1a), and the gripped article W is placed at a predetermined position in the rack 1a. Transport.

  Further, when the article W is stored in the predetermined rack 1a in this way, as shown in FIG. 8A, as the pair of forks 10 extend outward, the cage frames 6a and the fixed forks 10a are fixed to the fixed portions. The bending moment corresponding to the weight of the article W is gradually increased. For this reason, as the article W is conveyed into the rack 1a, it is bent and deformed so that the tip side of the tip movable fork 10c is arranged downward. In the present embodiment, even when the pair of forks 10 is bent and deformed in this way, the load receiving surface S1 of the lifting platform 6 is located above the placement surface S2 of the rack 1a. A lower end does not contact | abut to the corner | angular part (end part) of the outer side of the rack 1a. In addition, as the pair of forks 10 that grip the article W extend toward the inside of the rack 1a, the article W gripped by bending deformation is gradually arranged downward, so that the bottom surface of the article W and the mounting surface of the rack 1a The gap with S2 becomes smaller. As a result, when a pair of forks 10 described later is moved horizontally to release the gripping state of the article W, the article W falls and is placed on the placement surface S2 without receiving a large impact.

  Then, as described above, when the article W gripped by extending the pair of forks 10 is transported into the rack 1a, the gripped article W is opened as shown in FIGS. 7 (a) and 7 (b). When the opening operation is started (time T4), the control unit 14 first switches the current value I4 in the power running state of the first electric motor 11d to the current value I5 in the regenerative state. As a result, the pair of forks 10 starts to move so as to increase the distance between them, the gripping state of the article W is released, and the article W is placed on the placement surface S2 of the rack 1a. When the control means 14 switches the current value of the first motor 11d to the current value I5 in the power running state in this way, the first motor 11d is driven with a torque that accelerates the moving speed of the pair of forks 10. For this reason, the pair of forks 10 moves away from the article W while gradually increasing its moving speed. Next, when the moving speed of the pair of forks 10 reaches a preset maximum speed V3 at the time of opening (time T5), the control means 14 detects the maximum speed V3 and maintains the moving speed V3. Thus, the current value is switched to I3. As a result, the pair of forks 10 moves away from the article W at a constant speed V3. Next, at time T6 when the pair of forks 10 moving at a constant speed V3 approaches the initial position based on the size of the article W, the control means 14 uses the current value I3 of the first electric motor 11d in the regenerative state I2 Can be switched to. As a result, the moving speed of the pair of forks 10 decelerates and approaches the initial position while gradually decreasing the moving speed. Then, at time T7 when the pair of forks 10 return to the initial position at a moderate speed, the driving of the first electric motor 11d is stopped by the control means 14 and the opening operation is completed.

  On the other hand, when the article W stored in the rack 1a is delivered, the stacker crane 2 is moved horizontally and the elevator 6 that does not hold the article W is moved while the article W to be transported is stored in the rack 1a. Move closer. Then, when the lifting platform 6 approaches the predetermined rack 1a, as shown in FIG. 8 (b), the position detecting means 9 detects the placement surface S2 of the rack 1a and receives the detection result. 7 controls the elevating device 7 to stop the elevating platform 6 so that the load receiving surface S1 is positioned slightly below the placement surface S2 of the rack 1a. Thus, when the lifting platform 6 is stopped, the pair of forks 10 extends toward the inside of the rack 1a and grips the article W arranged between the pair of forks 10 by driving the first electric motor 11d. At this time, since the cargo receiving surface S1 is positioned slightly below the placement surface S2 of the rack 1a, the pair of forks 10 are also positioned below, and the lower end side of the article W is gripped by the pair of forks 10. The Also in this case, the article W is gripped with a suitable gripping force by the control means 14 controlling the current value of the first electric motor 11d as described above.

  Next, as shown in FIG. 8B, the pair of forks 10 is contracted, and the article W is delivered from the rack 1a. At this time, in the initial stage of the unloading operation, the bottom surface of the article W moves on the placement surface S2 of the rack 1a and the article W is pulled out. Then, the pair of forks 10 contracts, and the article W is completely supported by the pair of forks 10, and the pair of forks 10 are bent and deformed downward. Then, as the pair of forks 10 further shrinks, the articles W are arranged upward. For this reason, as the article W is approached, the article W is lifted upward, and since the article receiving surface S1 is positioned below the placement surface S2, the lower end of the article W is the end of the article receiving table 6b. There is no contact with the (corner).

  Therefore, according to the article transfer device (stacker crane) 2 of the present embodiment, the control means 14 for controlling the current value of the first electric motor 11d and controlling the driving of the first electric motor 11d is provided. The drive of the first electric motor 11d and the movement of the pair of forks 10 and thus the gripping force acting on the article W can be electrically controlled, which is more reliable than a conventional mechanical torque limiter that controls the gripping force. It is possible to prevent an excessive gripping force from acting on the article W.

  In addition, by providing the grip portion 15 on the inner surface that grips the article W of the pair of forks 10, the article W can be reliably gripped with a small gripping force, and the article W can be reliably prevented from being damaged. Furthermore, by providing such a gripping portion 15, the gripping force that is controlled so that the control means 14 can control the current value of the first electric motor 11 d so that the article W can be suitably gripped can be reliably and accurately applied to the article W. In addition, the article W can be gripped in a stable state.

  Further, the control means 16 connected to the lifting device 7 that has received the detection result of the position detection means 9 causes the load receiving surface S1 of the lifting platform 6 to be positioned above the placement surface S2 of the rack 1a when the article W is received. Since the lifting platform 6 can be stopped, it is possible to prevent the lower end of the article W from coming into contact with the rack 1a along with the warehousing. Further, at this time, the pair of forks 10 bend and deform as they extend toward the rack 1a, so that the separation between the placement surface S2 of the rack 1a and the bottom surface of the article W does not become too large, and the gripping of the article W is performed. When the state is released, the article W can be placed without causing a large impact. Moreover, since the lifting platform 6 is stopped when the cargo receiving surface S1 of the lifting platform 6 is positioned below the placement surface S2 of the rack 1a at the time of delivery, it is ensured that the lower end of the article W contacts the lifting platform 6. Can be prevented. Thereby, unlike the conventional article transfer device, when the article W is delivered, there is no need for the complicated work of moving the lifting platform 6 slightly upward when the article W is gripped by the pair of forks 10. For this reason, it is possible to efficiently carry in / out the goods W.

  Further, in the article transfer device 2 of the present embodiment, the pair of forks 10 that grip and convey the article W are formed by engaging a plurality of substantially flat members so as to be slidable with each other. The width of each of the pair of forks 10 can be made small, and the width dimension of the rack 1a of the hangar 1 can be formed so that the pair of forks 10 having a small width can be inserted into the width of the article W. Thereby, the dead space can be reduced and the rack 1a can be formed, and the article storage capacity of the automatic warehouse A can be improved.

  In addition, this invention is not limited to said one Embodiment, In the range which does not deviate from the meaning, it can change suitably. For example, in the present embodiment, the control means 14 for controlling the current value of the first electric motor 11d and the control means 16 connected to the lifting device 7 have been described as being provided individually. For example, other control means for controlling the operation of the stacker crane may be configured as the same control means.

  Further, in the present embodiment, the pair of forks 10 are each configured by one fixed fork 10a and two movable forks 10b and 10c. However, for example, the number of movable forks is one, or three or more. A pair of forks 10 may be configured.

  Furthermore, in the present embodiment, the grip portions 15 are provided on the inner surfaces of the pair of forks 10 facing each other. However, the grip portions 15 are provided only on the inner surface of one of the forks 10. It may be provided. When the grip portion 15 is provided only on one of the forks 10 as described above, for example, as shown in FIG. 9A, the grip 15 is mounted on the load receiving surface S1 of the lifting platform 6 (or the mounting surface S2 of the rack 1a). Even when the placed article W is inclined so that the side surfaces W1 gripped by the pair of forks 10 intersect with the inner surfaces of the pair of forks 10, as shown in FIG. Further, according to the gripping operation (horizontal movement or expansion / contraction) of the pair of forks 10, the position of the article W may be corrected and gripped so that the inner surfaces of the pair of forks 10 come into surface contact with the side surface W1 of the article W. it can. That is, as shown in FIG. 9A, the pair of forks 10 move horizontally, and the inner surfaces of the forks 10 come into contact with the corners W2 and W3 of the tilted article W, and The corner portion W <b> 2 with which the grip portion 15 provided on the inner surface of the fork 10 abuts is held at its abutting position by the frictional force with the grip portion 15, and the inner side of the other fork 10 without the grip portion 15. The corner W3 in contact with this surface slides in the inner surface of the other fork 10 by further horizontal movement or expansion or contraction of the pair of forks 10 or both horizontal movement and expansion and contraction. Thereby, according to the gripping operation of the pair of forks 10, the article W rotates around the corner W2 held by the gripping part 15, and the position of the article W is corrected. Finally, as shown in FIG. 9B, the article W such that the inner surfaces of the pair of forks 10 and the side surfaces W1 gripped by the pair of forks 10 of the article W are in surface contact. Is rotated and the position thereof is completely corrected, and the article W is gripped in a reliable and stable state by the pair of forks 10 as in the present embodiment. Therefore, by providing the grip portion 15 only on one of the forks 10 as described above, it is possible to reliably and stably grip the article W placed in an inclined state.

It is a perspective view which shows the automatic warehouse provided with the article transfer apparatus which concerns on one Embodiment of this invention. It is a perspective view which shows the article transfer apparatus which concerns on one Embodiment of this invention. It is a perspective view which shows the moving mechanism of a pair of fork and a pair of fork provided in the raising / lowering stand of the article transfer apparatus which concerns on one Embodiment of this invention. FIG. 4 is a perspective view showing a state in which a pair of forks in FIG. 3 is horizontally moved and extended. It is sectional drawing which shows the fork with which the article transfer apparatus which concerns on one Embodiment of this invention is comprised. It is a figure which shows a part of expansion-contraction movement mechanism of the fork | folk provided in the goods transfer apparatus which concerns on one Embodiment of this invention. It is a timing chart of the moving speed of a fork at the time of operation of a fork with which the article transfer device concerning one embodiment of the present invention is operated, and the current value of the 1st electric motor. It is a figure which shows the state of the goods receipt / entry operation | work with the goods transfer apparatus which concerns on one Embodiment of this invention. It is the figure which showed the operation | movement at the time of hold | gripping the inclined goods while showing the modification of a pair of fork of the goods transfer apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

1 Hangar 1a Rack 2 Stacker crane (article transfer device)
5a Mast 6 Lifting platform 6b Loading platform 7 Lifting device 9 Position detecting means 10 A pair of forks (forks)
10a fixed fork 10b intermediate movable fork 10c tip movable fork 11 horizontal movement mechanism 11d first electric motor 12 telescopic movement mechanism 12d second electric motor 13 current value sensor 14 control means 15 gripping part 16 control means A automatic warehouse S1 load receiving surface S2 of lifting platform Rack mounting surface W

Claims (2)

A mast erected so as to be movable in a substantially horizontal direction, a lifting platform supported so as to be movable up and down along the mast, a lifting device for lifting and lowering the lifting platform, and a hangar provided on the lifting platform and arranged in parallel In an article transfer apparatus comprising a pair of forks that are extendable in a direction opposite to the rack of the rack and move in a horizontal direction perpendicular to the opposite direction to grip the article,
An article transfer apparatus comprising a control means for controlling a gripping force for gripping the article by controlling a current value of a first electric motor for horizontally moving the pair of forks. The article transfer device according to claim 1,
The pair of forks is provided with a gripping portion having a relative coefficient of friction with respect to the article as compared with other parts on an inner surface for gripping the article of at least one of the forks. apparatus.

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