Patent Publication Number: US-2022234829-A1

Title: Conveyance system

Description:
FIELD 
     The present disclosure relates to a conveyance system. 
     BACKGROUND 
     Conventionally, systems comprising a conveyance device for conveying a workpiece to a processing machine are known. For example, Patent Literature 1 discloses a system comprising a loader which conveys a workpiece acquired from a workpiece feeder to a machine tool. The loader supplies the workpiece from the workpiece feeder to the machine tool, and conveys the workpiece from the machine tool to a removal location. The loader is controlled by a loader controller. When a plurality of identical workpieces are machined in the machine tool, in an initial cycle, the loader controller measures the time required for the machine tool to complete the machining of the workpiece (i.e., a loader standby time). The loader controller moves the loader at an acceleration/deceleration time constant and a maximum speed corresponding to the measured standby time in the second and subsequent cycles. With such a configuration, it is possible to prevent decreases in the operating efficiency of the loader and decreases in machining accuracy due to vibrations caused by high-speed movements and high acceleration/deceleration of the loader. 
     CITATION LIST 
     Patent Literature 
     
         
         [PTL 1] Japanese Patent No. 3925570 
       
    
     SUMMARY 
     Technical Problem 
     The system of Patent Literature 1 is advantageous when a plurality of identical workpieces are machined, as described above, since the machining time is the same in each cycle. However, when the machining time is different in each cycle (for example, when the system handles a wide variety of machined products), there is a risk that the system of Patent Literature 1 may be ineffective. 
     In consideration of such problems, the present invention aims to provide a conveyance system which enables a conveyance device to autonomously switch operations depending on the situation. 
     One aspect of the present disclosure provides a conveyance system for conveying a workpiece between a storage shelf and a plurality of processing machines, the conveyance system comprising (i) a main controller which receives a conveyance request for a workpiece from the plurality of processing machines, the main controller retaining the received conveyance request and transmitting a standby signal indicating whether or not a plurality of conveyance requests are retained in the main controller, and (ii) a conveyance device which conveys the workpiece between the storage shelf and the plurality of processing machines, the conveyance device comprising a carriage which moves between the storage shelf and the plurality of processing machines, and a local controller for controlling the carriage, wherein the local controller of the conveyance device is configured to receive the standby signal from the main controller, move the carriage in accordance with a first traveling control parameter when the standby signal indicates that a plurality of conveyance requests are retained in the main controller, and move the carriage in accordance with a second traveling control parameter, which moves the carriage more slowly than when moved in accordance with the first traveling control parameter, when the standby signal indicates that a plurality of conveyance requests are not retained in the main controller. 
     In the conveyance system according to the aspect of the present disclosure, when the main controller commands a subsequent conveyance to the conveyance device, a standby signal indicating whether or not a plurality of conveyance requests are retained in the main controller is transmitted to the local controller of the conveyance device. The local controller which received the standby signal moves the carriage in accordance with a first traveling control parameter when the standby signal indicates that a plurality of conveyance requests are retained in the main controller, and moves the carriage more slowly in accordance with a second traveling control parameter when the standby signal indicates that a plurality of conveyance requests are not retained in the main controller. Thus, the movement of the carriage is controlled only depending on whether or not a plurality of conveyance requests are retained in the main controller. Therefore, when a plurality of workpieces having different machining times are machined, the movement of the carriage can be controlled according to only the busy status of the conveyance system without considering the machining time of each workpiece. Thus, the conveyance device can autonomously switch the operation depending on the situation. Furthermore, when the conveyance system is not busy, the load on the conveyance device can be reduced by moving the carriage more slowly in accordance with the second traveling control parameter. 
     The standby signal may indicate only whether or not there is a second conveyance request at the time point at which the standby signal is sent by the main controller. In this case, for example, only one bit of data can be used, specifying 1 when there is a second conveyance request, and specifying 0 when there is no second conveyance request. Thus, increases in the amount of data transmitted from the main controller to the local controller can be minimized, and complicated processing can be avoided. 
     The first and second traveling control parameters may include a parameter of acceleration/deceleration of the carriage. When accelerating or decelerating, a large moment is exerted on the components of the conveyance device. Thus, by adjusting the acceleration/deceleration parameter of the carriage, the load on the conveyance device can be more efficiently reduced. 
     SUMMARY 
     According to the aspect of the present disclosure, a conveyance system which enables a conveyance device to autonomously switch operations depending on the situation can be provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic top view showing a production system comprising a conveyance system according to an embodiment. 
         FIG. 2  is a schematic side view showing the production system of  FIG. 1 . 
         FIG. 3  shows an example of a conveyance request for a workpiece retained in a main controller. 
         FIG. 4  shows an example of a conveyance request for a workpiece retained in a main controller. 
         FIG. 5  shows an example of a conveyance request for a workpiece retained in a main controller. 
         FIG. 6  is a flowchart showing conveyance system operations. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The conveyance system according to an embodiment will be described below with reference to the attached drawings. Identical or corresponding elements have been assigned the same reference signs, and duplicate descriptions thereof have been omitted. To facilitate understanding, the scales of the drawings have been modified in some cases. 
       FIG. 1  is a schematic top view showing a production system  200  comprising a conveyance system  190  according to an embodiment, and  FIG. 2  is a schematic side view showing the production system  200  of  FIG. 1 . Referring to  FIG. 1 , in the production system  200 , workpieces W are conveyed between a pallet stocker (storage shelf)  2 , processing machines  1 A,  1 B, and workpiece setup stations (WSS; hereinafter also referred to simply as “stations”)  3 A,  3 B by the conveyance system  190 . The production system  200  may handle a wide variety of machined products having, for example, different machining times. Referring to  FIG. 2 , the workpieces W may be attached to, for example, pallets P, and the pallets P may be carried by a conveyance device  100 . In another embodiment, the workpieces W may be directly carried by the conveyance device  100 . Referring to  FIG. 1 , the production system  200  comprises a plurality of processing machines  1 A,  1 B, the pallet stocker  2 , the stations  3 A,  3 B, and the conveyance system  190 . The production system  200  may further comprise other constituent elements. Note that in  FIG. 2 , in order to facilitate understanding, some components such as the processing machines  1 A,  1 B and the stations  3 A,  3 B are not shown. 
     Referring to  FIG. 1 , the processing machines  1 A,  1 B can be any of various types of machine tools, such as machining centers. For example, each processing machine  1 A,  1 B has a pallet changer PC which is capable of exchanging a pallet P having an unmachined workpiece W with a pallet P having a machined workpiece W. Furthermore, the processing machines  1 A,  1 B have respective local controllers  160 A,  160 B (which will be described in detail later) for controlling the processing machines  1 A,  1 B. 
     In the stations  3 A,  3 B, an operator can attach a workpiece W to a pallet P and can remove a workpiece W from a pallet P. The stations  3 A,  3 B have respective local controllers  170 A,  170 B (which will be described in detail later) for controlling the stations  3 A,  3 B. 
     Referring to  FIG. 2 , the pallet stocker  2  can house pallets P with or without a workpiece W. The pallet stocker  2  has a plurality of stock areas S (two rows×10 columns in  FIG. 2 ) having differing heights for housing pallets P. For example, each stock area S can have a pair of leg members Sa for supporting the pallets P. 
     The conveyance system  190  comprises the conveyance device  100  and a main controller  150 . The conveyance device  100  comprises a carriage  10 , a support column  20 , a lifting device  30 , a loading platform  90 , and a slide device  80 . Furthermore, referring to  FIG. 1 , the conveyance device  100  comprises a local controller  70  for controlling the various constituent elements of the conveyance device  100 . The conveyance device  100  may further comprise other constituent elements. 
     The carriage  10  is configured so as to travel horizontally along rails R, and can move between the pallet stocker  2 , the processing machines  1 A,  1 B, and the stations  3 A,  3 B. In the present embodiment, the carriage  10  travels along two rails R. In another embodiment, the carriage  10  may travel along a single rail R. The carriage  10  can be driven by, for example, a servomotor (not illustrated). The driving of the servomotor (i.e., the X direction traveling of the carriage  10 ) can be controlled by the local controller  70 . 
     Regarding the coordinate axes with respect to the conveyance device  100 , the axis parallel to the direction in which the carriage  10  moves (also referred to as the “forward-rearward directions”) is the X-axis (also referred to as the “travel axis”). With respect to the support column  20 , the side on which the loading platform  90  is present is the “front”, and the side opposite thereto is the “rear.” Among horizontal directions, the direction orthogonal to the front-rear direction is the left-right direction, and the axis parallel to the left-right direction (i.e., the horizontal axis orthogonal to the X-axis) is the Z-axis (also referred to as the “transfer axis”). The axis parallel to the vertical direction (also referred to as the “up-down directions”) is the Y-axis (also referred to as the “elevation axis”). 
     The support column  20  protrudes vertically upward from the carriage  10 . The lifting device  30  moves in the up-down directions along the support column  20 . The lifting device  30  is driven by a motor M. The motor M can be, for example, a servomotor. The driving of the motor M (i.e., the Y direction movement of the lifting device  30 ) can be controlled by the local controller  70 . The loading platform  90  is supported by the lifting device  30  and is moved in the up-down directions by the lifting device  30 . 
     The slide device  80  is provided on the loading platform  90 . The slide device  80  has one or a plurality of slide members which move in the left-right directions relative to the loading platform  90 , and which can access the processing machines  1 A,  1 B, the pallet stocker  2 , and the stations  3 A,  3 B. The slide device  80  has a fork which is capable of engaging with pallets P. The slide members can be driven by, for example, a servomotor (not illustrated). The driving of the servomotor (i.e., the Z direction movement of the slide device  80 ) can be controlled by the local controller  70 . 
     The local controller  70  is capable of communicating by wire or wirelessly with the motors for driving the carriage  10 , the lifting device  30 , and the slide device  80 , and is configured so as to control the carriage  10 , the lifting device  30 , and the slide device  80 . The local controller  70  may further control other constituent elements of the conveyance device  100  (which will be described in detail later). 
     The main controller  150  is capable of communicating by wire or wirelessly with each of the local controllers described above, and is configured so as to control all conveyance in the production system  200  (which will be described in detail later). 
     Next, the main controller  150  and the local controllers  70 ,  160 A,  160 B,  170 A,  170 B will be described in detail. 
     The local controllers  70 ,  160 A,  160 B,  170 A,  170 B each comprise a processor (for example, a CPU (Central Processing Unit))  71 ,  161 ,  171 , and a memory (for example, a hard disk drive)  72 ,  162 ,  172 . Furthermore, the local controllers  70 ,  160 A,  160 B,  170 A,  170 B can each comprise other constituent elements such as ROM (read-only memory), RAM (random access memory), and an input device and/or output device (for example, mouse, keyboard, liquid crystal display, and/or touch panel, etc.), and the constituent elements of each local controller can be connected to each other via busses or the like. The processors  71 ,  161 ,  171  can execute various processes, including the processes described below, in accordance with programs stored in, for example, the memories  72 ,  162 ,  172 . The memories  72 ,  162 ,  172  can store various data including various programs used by the processors  71 ,  161 ,  171 . The main controller  150 , in the same manner as the local controllers, can comprise, for example, a processor  151  and a memory  152 , and can comprise other constituent elements such as ROM, RAM and an input device and/or output device. 
     Each of the local controllers  160 A,  160 B of the processing machines  1 A,  1 B can transmit, for example, prior to machining, a workpiece W conveyance request to the main controller  150  to convey a workpiece W from the pallet stocker  2  or the stations  3 A,  3 B to the pallet changer PC. Furthermore, each of the local controllers  160 A,  160 B can transmit, after machining, a workpiece W conveyance request to the main controller  150  to convey the workpiece W from the pallet changer PC to the pallet stocker  2  or the stations  3 A,  3 B. 
     Each of the local controllers  170 A,  170 B of the stations  3 A,  3 B can transmit a workpiece W conveyance request to the main controller  150  to convey, for example, prior to attachment of the workpiece W to the pallet P, an empty pallet P from the pallet stocker  2  to the stations  3 A,  3 B. Furthermore, each of the local controllers  170 A,  170 B of the stations  3 A,  3 B, after attachment of the workpiece W to the pallet P, can transmit a workpiece W conveyance request to the main controller  150  to convey the workpiece W from the stations  3 A,  3 B to the pallet stocker  2  or the processing machines  1 A,  1 B. 
     The main controller  150  receives the conveyance requests described above, which are transmitted from the local controllers  160 A,  160 B,  170 A,  170 B. The main controller  150  retains the received conveyance requests in, for example, a storage device such as the memory  152 . When a plurality of conveyance requests are retained, the main controller  150  may, for example, retain the conveyance requests in the order in which they are received, or when necessary, may change the order of the conveyance requests. 
     The main controller  150  transmits data necessary for a subsequent conveyance to the local controller  70  of the conveyance device  100 . Specifically, the main controller  150  transmits, for example, a conveyance source and conveyance destination of a workpiece W of a subsequent conveyance request (a first conveyance request at the time point at which the standby signal is transmitted) to the local controller  70 . Simultaneously, the main controller  150  transmits a standby signal indicating whether or not a plurality of conveyance requests are retained in the main controller  150  to the local controller  70 . Specifically, the standby signal represents only whether or not there is a second conveyance request at the time point at which the standby signal is transmitted. More specifically, the main controller  150  uses only one bit for the standby signal, specifying 1 when there is a second conveyance request, and specifying 0 when there is no second conveyance request. The main controller may delete the corresponding conveyance request from the storage device after the above data necessary for a subsequent conveyance has been transmitted to the local controller  70  or after a conveyance complete signal has been received from the local controllers  160 A,  160 B,  170 A,  170 B. 
     The local controller  70  of the conveyance device  100  receives the above data transmitted from the main controller  150 . The local controller  70  moves the carriage  10  in accordance with a first traveling control parameter when the standby signal indicates that a plurality of conveyance requests are retained in the main controller  150  at the time of a subsequent conveyance. For example, the first traveling control parameter may be intended to be used in normal traveling of the carriage  10 . Furthermore, the local controller  70  moves the carriage  10  in accordance with a second traveling control parameter, by which the carriage  10  moves more slowly than when moved in accordance with the first traveling control parameter, when the standby signal indicates that a plurality of conveyance requests are not retained in the main controller  150  at the time of a subsequent conveyance. By moving the carriage  10  in accordance with the second traveling control parameter, the load on the conveyance device  100  can be reduced as compared with the case in which the carriage  10  is moved in accordance with the first traveling control parameter. Specifically, the first and second traveling control parameters may include a parameter related to the acceleration/deceleration of the carriage  10 . More specifically, the first and second traveling control parameters may be acceleration in the acceleration/deceleration operations of the carriage  10 . Specifically, the acceleration of the second traveling control parameter (which can also be referred to as deceleration in deceleration operations) is lower than the acceleration of the first traveling control parameter. The first and second control parameters can be stored in advance in a storage device such as the memory  72 . 
     Next, the operations of the conveyance system  190  will be described. 
       FIGS. 3, 4, and 5  show examples of workpiece W conveyance requests retained in the main controller  150 , and  FIG. 6  is a flowchart showing the operations of the conveyance system  190 . Referring to  FIG. 3 , in this example, at the time point at which the standby signal is transmitted from the main controller  150  to the local controller  70  of the conveyance device  100 , an nth conveyance request (a first conveyance request at the time point at which the standby signal is transmitted) and an (n+1)th conveyance request (a second conveyance request at the time point at which the standby signal is transmitted) are retained in the main controller  150 . 
     In this case, referring to  FIG. 6 , the processor  151  of the main controller  150  transmits data including the conveyance source and conveyance destination of the nth conveyance request and the standby signal to the local controller  70  of the conveyance device  100  (step S 100 ), and the transmitted data is received by the local controller  70  (step S 102 ). Next, a processor  71  of the local controller  70  determines whether or not the received standby signal indicates that a plurality of conveyance requests are retained in the main controller  150  (step S 104 ). In the example of  FIG. 3 , as described above, since the nth and (n+1)th conveyance requests are retained in the main controller  150  at the time point at which the standby signal is transmitted, it is determined in step S 104  that a plurality of conveyance requests are retained in the main controller  150 . Thus, the processor  71  moves the carriage  10  in accordance with the first traveling control parameter, conveys a workpiece W from the conveyance source to the conveyance destination, which are included in the received data (step S 106 ), and ends the series of operations. 
     Referring to  FIG. 4 , in this example, only an nth conveyance request is retained in the main controller  150  at the time point at which the standby signal is transmitted from the main controller  150  the local controller  70 . 
     In this case, referring to  FIG. 6 , the processor  151  transmits data including the conveyance source and conveyance destination of the nth conveyance request and the standby signal to the local controller  70  (step S 100 ), and the transmitted data is received by the local controller  70  (step S 102 ). Next, the processor  71  of the local controller  70  determines whether or not the received standby signal indicates that a plurality of conveyance requests are retained in the main controller  150  (step S 104 ). In the example of  FIG. 4 , as described above, since only the nth conveyance request is retained in the main controller  150  at the time point at which the standby signal is transmitted, it is determined in step S 104  that a plurality of conveyance requests are not retained in the main controller  150 . Thus, the processor  71  moves the carriage  10  in accordance with the second traveling control parameter, conveys the workpiece W from the conveyance source to the conveyance destination, which are included in the received data (step S 108 ), and ends the series of operations. 
     Referring to  FIG. 5 , in this example, only the nth conveyance request is retained in the main controller  150  at the time point at which the standby signal is transmitted from the main controller  150  to the local controller  70 , and when the conveyance device  100  moves based on the nth conveyance request, an (n+1)th conveyance request is received by the main controller  150 . 
     In this case, referring to  FIG. 6 , the processor  151  transmits data including the conveyance source and conveyance destination of the nth conveyance request and the standby signal to the local controller  70  (step S 100 ), and the transmitted data is received by the local controller  70  (step S 102 ). Next, the processor  71  of the local controller  70  determines whether or not the received standby signal indicates that a plurality of conveyance requests are retained in the main controller  150  (step S 104 ). In the example of  FIG. 5 , as described above, since only the nth conveyance request is retained in the main controller  150  at the time point at which the standby signal is transmitted, in step S 104 , it is determined that a plurality of conveyance requests are not retained in the main controller  150 . Thus, the processor  71  moves the carriage  10  in accordance with the second traveling control parameter, conveys a workpiece W from the conveyance source to the conveyance destination, which are included in the received data (step S 108 ), and ends the series of operations. 
     In the conveyance system  190  as described above, when the main controller  150  commands a subsequent conveyance to the conveyance device  100 , a standby signal indicating whether or not a plurality of conveyance requests are retained in the main controller  150  is transmitted to the local controller  70  of the conveyance device  100 . The local controller  70  which received the standby signal moves the carriage  10  in accordance with the first traveling control parameter when the standby signal indicates that a plurality of conveyance requests are retained in the main controller  150 , and moves the carriage  10  more slowly in accordance with the second traveling control parameter when the standby signal indicates that a plurality of conveyance requests are not retained in the main controller  150 . Thus, the movement of the carriage  10  is controlled in accordance with only whether or not a plurality of conveyance requests are retained in the main controller  150 . Therefore, when a plurality of workpieces W having different machining times are machined, the movement of the carriage  10  can be controlled only according to the busy situation of the conveyance system  190  without considering the machining time of each workpiece W. Thus, the conveyance device  100  can autonomously switch operations in accordance with the situation. Furthermore, when the conveyance system  190  is not busy, the load on the conveyance device  100  can be reduced by moving the carriage  10  more slowly in accordance with the second traveling control parameter. 
     Furthermore, in the conveyance system  190 , the standby signal indicates only whether or not there is a second conveyance request at the time point at which the main controller  150  transmits the standby signal. Thus, only one bit of data can be used, specifying 1 when there is a second conveyance request, and specifying 0 when there is no second conveyance request. Thus, increases in the amount of data transmitted from the main controller  150  to the local controller  70  can be minimized, and complicated processing can be avoided. 
     Furthermore, in the conveyance system  190 , the first and second traveling control parameters include parameters of acceleration/deceleration of the carriage  10 , and specifically, acceleration in the acceleration/deceleration operations. During acceleration or deceleration, a large moment is exerted on the components of the conveyance device  100 . Thus, by adjusting the acceleration/deceleration parameters of the carriage  10 , the load on the conveyance device  100  can be reduced more efficiently. 
     Though the embodiments of the conveyance system have been described, the present invention is not limited to the above embodiments. A person skilled in the art would understand that various modifications can be made to the above embodiments. For example, in the above embodiments, the traveling control parameters include acceleration in the acceleration/deceleration operation of the carriage  10 . However, in another embodiment, the traveling control parameters may include other parameters (for example, speed, jerk, etc., of the carriage  10 ). 
     Furthermore, in the above embodiments, the local controller  70  of the conveyance device  100  adjusts only the movement of the carriage  10  based on whether or not a plurality of conveyance requests are retained in the main controller  150 . However, in another embodiment, the local controller  70  may further adjust at least one of the movement of the lifting device  30  and the slide device  80  in the same manner as the carriage  10 . Specifically, the local controller  70  may raise and lower the lifting device  30  in accordance with a first lifting/lowering control parameter (for example, acceleration of the lifting device  30 ) when the standby signal indicates that a plurality of conveyance requests are retained in the main controller  150 , and may raise and lower the lifting device  30  in accordance with a second lifting/lowering control parameter, in which the lifting device  30  is moved more slowly than the movement in accordance with the first lifting/lowering control parameter, when the standby signal indicates that a plurality of conveyance requests are not retained in the main controller  150 . Likewise, the local controller  70  may advance and retract the slide device  80  in accordance with a first transfer control parameter (for example, acceleration of the slide device  80 ) when the standby signal indicates that a plurality of conveyance requests are retained in the main controller  150 , and may advance and retract the slide device  80  by a second transfer control parameter, in which the slide device  80  moves more slowly than the movement in accordance with the first transfer control parameter, when the standby signal indicates that a plurality of conveyance requests are not retained in the main controller  150 . 
     DESCRIPTION OF REFERENCE SIGNS 
     
         
           1 A Processing Machine 
           1 B Processing Machine 
           2  Pallet Stocker (Storage Shelf) 
           10  Carriage 
           70  Local Controller 
           100  Conveyance Device 
           150  Main Controller 
           190  Conveyance System 
         W Workpiece