Conveyor system

Abstract

A conveying system having a plurality of conveyor cars and a controller. The travel path has a first path, a second path, and a merging section where the first and second paths converge. The controller performs either priority control or non-priority control; priority control ensures that a conveyor car traveling on one of the first or second paths (defined as priority paths) passes through the merging section with priority over a conveyor car traveling on the other; non-priority control ensures that the conveyor car passes through the merging section in a manner that does not prioritize the conveyor car based on whether it travels on the first or second path; when a congestion of a conveyor car occurs in a predetermined target area on the first or second path upstream of the merging section, the controller performs non-priority control; when no congestion of a conveyor car occurs in the target area, the controller performs priority control.

Description

Transportation System The present invention relates to a transportation system. As described in Patent Document 1, a transportation system (transport vehicle system) is known, which includes: a travel path having a first path, a second path having a standby section, and a confluence section where the first path and the second path merge; a plurality of transport vehicles that travel on the travel path; and a controller that controls the travel of the plurality of transport vehicles. In this transportation system, until a predetermined number of transport vehicles are parked at the standby section of the second path, while causing the transport vehicles traveling on the second path to wait at the standby section, the transport vehicles traveling on the first path are continuously passed through the confluence section. [Prior Art Documents] [Patent Documents] Patent Document 1: International Publication No. 2010 / 035411 (Problems to be Solved by the Invention) Here, in the above-mentioned conventional system, the transport vehicle is parked at the standby section until a predetermined number of transport vehicles are parked at the standby section of the second path. When the waiting time of the transport vehicle at the standby section is too long, the transport vehicle is detained at the standby section for a long time, so the transport efficiency is very low. In order to prevent the waiting time of the transport vehicle at the standby section from becoming too long, it is considered to set a limit on the waiting time and execute control to cause the transport vehicle whose waiting time has reached a predetermined time or more to travel on another travel path and bypass the confluence section (avoid dead lock escape (DLE)). However, bypassing the confluence section will increase the travel distance of the transport vehicle, and as a result, the transport efficiency will decrease. Regarding this problem, it is considered to execute control by the controller to alternately pass the transport vehicle traveling on the first path and the transport vehicle traveling on the second path through the confluence section, thereby suppressing the occurrence of the transport vehicle being detained at the standby section. However, this will cause the transport vehicle to repeatedly start and stop, and as a result, the transport efficiency will decrease. The present disclosure describes a transportation system that can improve transportation efficiency. (Technical Means for Solving the Problem) A transport system according to an aspect of the present invention includes: a plurality of transport vehicles that travel on a travel path and transport articles; and a controller that controls the travel of the plurality of transport vehicles; the travel path has a first path, a second path different from the first path, and a confluence section where the first path and the second path merge; the controller executes either priority control or non-priority control; the priority control causes a transport vehicle traveling on one of the first path and the second path set as a priority path to pass through the confluence section preferentially over a transport vehicle traveling on the other path; the non-priority control causes the transport vehicles to pass through the confluence section in a manner that does not distinguish between superiority and inferiority depending on which of the first path and the second path the transport vehicle travels on. When a blockage of a transport vehicle occurs in a predetermined determination target area upstream of the confluence section on the first path or the second path, the controller executes non-priority control. When no blockage of a transport vehicle occurs in the determination target area, the controller executes priority control. In this transport system, when a blockage of a transport vehicle occurs in the determination target area, the controller executes non-priority control. In non-priority control, the transport vehicles are caused to pass through the confluence section in a manner that does not distinguish between superiority and inferiority depending on the travel path of the transport vehicle, so that the blockage of the transport vehicles in the determination target area can be eliminated. Also, in this transport system, when no blockage of a transport vehicle occurs in the determination target area, the controller executes priority control. In priority control, a transport vehicle traveling on one of the first path and the second path set as a priority path passes through the confluence section preferentially over a transport vehicle traveling on the other path. Thereby, when a transport vehicle of one side passes through the confluence section, it does not need to wait until a transport vehicle of the other side passes through the confluence section. As a result, a transport vehicle of one side can pass through the confluence section without repeatedly starting and stopping. Based on the above, the transport efficiency can be improved. In non-priority control, it is also possible to cause the transport vehicles traveling on the first path and the transport vehicles traveling on the second path to alternately pass through the confluence section. When this is the case, by causing the transport vehicles traveling on the first path and the transport vehicles traveling on the second path to alternately pass through the confluence section, the blockage of the transport vehicles in the determination target area can be surely eliminated. The controller can also determine that a blockage of a transport vehicle occurs in the determination target area when there are a predetermined number or more of transport vehicles within a predetermined distance from a transport vehicle located in front of the own vehicle in the determination target area. When this is the case, it is possible to determine whether there is a blockage of a transport vehicle based on the number of transport vehicles approaching each other in the determination target area. Thereby, it is possible to easily determine the blockage of a transport vehicle in the determination target area. The transport vehicle may also have: a measurement unit that measures the distance to a transport vehicle in front of the vehicle; and a travel control unit that stops the vehicle when the distance is equal to or less than a predetermined distance. When the controller controls using the travel control unit and determines that there are a predetermined number or more of stopped transport vehicles in the determination target area, it determines that a blockage of the transport vehicle has occurred in the determination target area. In this case, it can determine whether there is a blockage of the transport vehicle based on the number of stopped transport vehicles controlled by the travel control unit in the determination target area. Thereby, it can more easily determine the blockage of the transport vehicle in the determination target area. The determination target area may also include: a connection path that is connected to a confluence section; and a plurality of confluence paths that converge to the connection path. For example, when the connection path does not have a sufficient length, etc., it may be difficult to determine whether there is a blockage only from the travel status on the connection path. By considering not only the connection path but also the number of transport vehicles on the plurality of confluence paths, etc., it can correctly determine whether there is a blockage regardless of the layout of the travel path. (Effect compared to the prior art) According to the present invention, the transport efficiency can be improved. Hereinafter, embodiments of the present invention will be described with reference to the drawings. Furthermore, in the description of the drawings, the same reference numerals are assigned to the same components, and the repeated description thereof is omitted. First, with reference to FIGS. 1 and 2, an overview of the transport system 1 will be described. As shown in FIG. 1, the transport system 1 is a system for transporting articles (not shown). The article is, for example, a container such as a front-opening wafer cassette (FOUP, Front Opening Unified Pod) that stores a plurality of semiconductor wafers. The article may also be a reticle box that stores a glass substrate, or other general components. The transport system 1 includes a track (travel path) 2, a plurality of transport vehicles 3, and a controller 4. The track 2 is a predetermined travel path for moving the transport vehicle 3. The track 2 is, for example, laid near the ceiling, which is the overhead space of the operator. The track 2 is, for example, suspended from the ceiling via a plurality of columns (not shown). The track 2 is formed by connecting a plurality of path portions 20 to each other. The track 2 has: a confluence section 21 formed by the confluence of a plurality of path portions 20, and a branch section 22 where one path portion 20 branches into a plurality of path portions 20. The layout of the track 2 (the shape, length, and arrangement of the path portions 20, and the positions of the confluence section 21 and the branch section 22) is not particularly limited, and various layouts can be adopted. The plurality of path portions 20 include, for example, a plurality of straight paths 23 and a plurality of curved paths 24. In the example shown in FIG. 1, the plurality of straight paths 23 include a plurality of first straight paths 27, a second straight path 28, and a third straight path 29 that are parallel and extend in a fixed direction. The second straight path 28 is disposed between the first straight path 27 and the third straight path 29. Although not shown, as the entire track 2, there are a plurality of straight paths and the like that extend in a direction other than the fixed direction (for example, in a direction orthogonal to the fixed direction). In this specification, the terms "upstream side" and "downstream side" are used based on the traveling direction of the carrier 3. The curved path 24 branches via a branch portion 22 in the middle of a certain straight path 23 and merges via a merging portion 21 in the middle of another straight path 23. The plurality of curved paths 24 include an S-shaped path 25 and a U-shaped path 26. The S-shaped path 25 is used to change the path of the straight path 23 along which the carrier 3 travels without changing the traveling direction of the carrier 3. In the present embodiment, the S-shaped path 25 connects the first straight path 27 and the second straight path 28 to each other. The U-shaped path 26 is used to change the path of the straight path 23 along which the carrier 3 travels when changing the traveling direction of the carrier 3. The U-shaped path 26 connects the second straight path 28 and the third straight path 29 to each other. In the example shown in FIG. 1, the U-shaped path 26 is located on the downstream side of the S-shaped path 25. Hereinafter, there is a case where the merging portion 21 where the U-shaped path 26 and the third straight path 29 merge is referred to as the merging portion 21a, and the merging portion 21 where the S-shaped path 25 and the second straight path 28 merge is referred to as the merging portion 21b. Also, there is a case where the branch portion 22 where the second straight path 28 branches toward the U-shaped path 26 is referred to as the branch portion 22a, and the branch portion 22 where the first straight path 27 branches toward the S-shaped path 25 is referred to as the branch portion 22b. If the track 2 is described from a different perspective from the above description, the track 2 has a first path R1, a second path R2 different from the first path R1, and a merging portion 21 where the first path R1 and the second path R2 merge. Both the first path R1 and the second path R2 are paths that are located upstream of the merging portion 21 and are connected to the merging portion 21. The first path R1 that merges into the merging portion 21a includes: a connecting path 51 that is connected to the merging portion 21a; and a plurality of merging paths 52 that merge into the connecting path 51 at the merging portion 21b. The second path R2 that merges into the merging portion 21a includes, for example, a portion of the third straight path 29 that is upstream of the merging portion 21a. In the present embodiment, the connection path 51 includes a U-shaped path 26 and a portion of the second straight path 28 that is upstream of the branch portion 22a and downstream of the confluence portion 21b. The plurality of confluence paths 52 include a portion of the second straight path 28 that is upstream of the confluence portion 21b. The plurality of confluence paths 52 include an S-shaped path 25 and a portion of the first straight path 27 that is upstream of the branch portion 22b. On the track 2, a plurality of stop points T, which are positions for stopping the carrier vehicle 3, are provided. The stop points T are provided at preset positions. The stop points T are set, for example, with reference to a plurality of point markers (not shown) such as barcodes attached at predetermined intervals along the track 2. In the figure, the stop points T are represented by dotted circles on the track 2. The carrier vehicle 3 travels along the track 2 in the traveling direction and transports articles. The carrier vehicle 3 transports articles, for example, according to a transport instruction assigned by the controller 4. The transport instruction includes, for example, information related to the transfer of articles at the transport departure point, the travel along the path from the transport departure point to the transport destination, and the transfer of articles at the transport destination. The carrier vehicle 3 is configured to be able to transfer articles to a port (not shown). The carrier vehicle 3 is an overhead traveling unmanned vehicle. The carrier vehicle 3 is also referred to as a traveling vehicle, a transport cart, or an overhead traveling vehicle (overhead traveling cart), for example. The number of carrier vehicles 3 included in the transport system 1 is not particularly limited. The carrier vehicle 3 has, for example, a traveling unit (not shown), a θ driver, a lateral transport unit, a lifting drive unit, and a lifting table. The traveling unit causes the carrier vehicle 3 to travel along the track 2. The θ driver causes the lifting drive unit to rotate in the horizontal plane and controls the posture of the article. The lateral transport unit laterally transports the portion below the θ driver relative to the track 2. The lifting drive unit raises and lowers the lifting table that holds the article. A chuck is provided on the lifting table and is configured to be able to hold or release the article freely. However, the configuration of the carrier vehicle 3 can be changed appropriately. As shown in FIG. 2, the carrier vehicle 3 has a position acquisition unit 31, a measurement unit 32, and a travel control unit 33 as its functional components. The position acquisition unit 31 acquires position information indicating the position of the carrier vehicle 3 on the track 2. The position acquisition unit 31 is composed of, for example, a reading unit that reads the point markers on the track 2 and an encoder. The position information includes, for example, information on the point markers obtained by the reading unit and information related to the travel distance after passing the point markers. The position acquisition unit 31 sends the acquired position information to the travel control unit 33. The measurement unit 32 measures the distance between the vehicle itself (the transport vehicle 3 equipped with the measurement unit 32) and the transport vehicle 3 located in front of the vehicle itself. The front herein means the front in the traveling direction of the transport vehicle 3. The measurement unit 32 is, for example, a vehicle distance sensor that detects the interval between the vehicle itself and the transport vehicle 3 existing in front of the vehicle itself. The measurement unit 32, for example, emits laser light toward the front of the vehicle itself and detects the reflected light reflected by the reflector of the transport vehicle 3 in front, thereby detecting the distance between the vehicle itself and the transport vehicle 3 in front of the vehicle itself. The measurement unit 32 transmits the measured distance to the travel control unit 33. The travel control unit 33 is an electronic control unit including a central processing unit (CPU, Central Processing Unit), a read-only memory (ROM, Read Only Memory), a random access memory (RAM, Random Access Memory), and the like. The travel control unit 33 is, for example, constituted by software that can load the program stored in the ROM onto the RAM and execute it using the CPU. The travel control unit 33 can also be constituted by hardware formed by an electronic circuit or the like. The travel control unit 33 controls various operations of the transport vehicle 3. The travel control unit 33 controls the travel unit and the measurement unit 32. The travel control unit 33 can communicate with the controller 4. The travel control unit 33, for example, can communicate with the controller 4 via the power feeding line of the track 2 or the like, and can also communicate with the controller 4 via a communication line (feed line or the like) provided along the track 2 different from the power feeding line. When the travel control unit 33 receives a status query from the controller 4, it sends a status report of the vehicle itself to the controller 4. The travel control unit 33 determines whether the distance between the vehicle itself and the transport vehicle 3 in front of the vehicle itself is below a predetermined distance based on the detection result of the measurement unit 32. This predetermined distance is, for example, set in advance and can be appropriately changed. When the distance is below the predetermined distance, the travel control unit 33 performs stop control to stop the vehicle itself by controlling the travel unit. The travel control unit 33 includes the position information obtained by the position acquisition unit 31 and the information indicating that the stop control is being executed in the status report and sends it to the controller 4. The travel control unit 33 pre-memorizes the layout of the track 2. The layout of the track 2 includes information indicating the positions of each path portion 20, each merging portion 21, and each branching portion 22. The travel control unit 33 determines whether the vehicle itself intends to pass through the merging portion 21 based on the preset travel vehicle speed of the vehicle itself, the layout of the track 2, and the position information of the vehicle itself. The travel control unit 33, for example, determines that the vehicle itself intends to pass through the merging portion 21 when it reaches a position where the time required for travel until the merging portion 21 is less than a predetermined time. The travel control unit 33 determines whether the vehicle intends to pass through the branch portion 22 based on the preset travel speed of the vehicle itself, the layout of the track 2, and the position information of the vehicle itself. For example, when the vehicle reaches a position where the time required for travel until the branch portion 22 is less than a predetermined time, the travel control unit 33 determines that the vehicle intends to pass through the branch portion 22. When the vehicle intends to pass through the merging portion 21, the travel control unit 33 includes a merging portion passage permission request in the status report near the merging portion 21 and transmits it to the controller 4. For example, when the distance from the vehicle to the merging portion 21 becomes equal to or less than a predetermined distance, the travel control unit 33 transmits the merging portion passage permission request to the controller 4. The predetermined distance is preset, and as an example, it is 8 m. The predetermined distance can be appropriately changed. The merging portion passage permission request is a signal requesting permission to pass through the merging portion 21. When the travel control unit 33 receives a merging portion passage permission response from the controller 4, it controls the travel unit to move the vehicle into the merging portion 21. The merging portion passage permission response is a signal permitting passage through the merging portion 21. When the travel control unit 33 does not receive a merging portion passage permission response from the controller 4, it controls the travel unit to stop the vehicle at the stop point T near the merging portion 21 and wait. However, the position where the vehicle stops before passing through the merging portion 21 can also be appropriately changed. When the vehicle intends to pass through the branch portion 22, the travel control unit 33 includes a branch portion passage permission request in the status report near the branch portion 22 and transmits it to the controller 4. The branch portion passage permission request is a signal requesting permission to pass through the branch portion 22. When the travel control unit 33 receives a branch portion passage permission response from the controller 4, it controls the travel unit to move the vehicle into the branch portion 22. The branch portion passage permission response is a signal permitting passage through the branch portion 22. When the travel control unit 33 does not receive a branch portion passage permission response from the controller 4, it controls the travel unit to stop the vehicle at the stop point T near the branch portion 22 and wait. However, the position where the vehicle stops before passing through the branch portion 22 can also be appropriately changed. The controller 4 is an electronic control unit including a CPU, a ROM, a RAM, etc. For example, the controller 4 can be configured such that a program stored in the ROM is loaded onto the RAM and executed by the CPU. The controller 4 can also be configured as hardware formed by an electronic circuit or the like. The controller 4 has a carrier control unit 41, a blockage determination unit 42, and a control switching unit 43. The carrier control unit 41 communicates with a plurality of carriers 3 within its jurisdiction area to control the plurality of carriers 3. The carrier control unit 41 controls the movement of the plurality of carriers 3 by communicating with the movement control unit 33 included in the carrier 3. The carrier control unit 41 communicates with a host controller (not shown) by wire or wirelessly. The carrier control unit 41, for example, generates a conveyance instruction according to a conveyance request given from the host controller, and distributes the conveyance instruction to the carrier 3. The carrier control unit 41 performs periodic communication with a plurality of carriers 3 within the jurisdiction area. For example, the carrier control unit 41 sends a status query to the carriers 3 within the jurisdiction area, and receives a status report from the carriers 3 that have received the status query. This communication is sequentially and periodically performed with a plurality of carriers 3 within the jurisdiction area, so that the carrier control unit 41 can grasp the status of the plurality of carriers 3 within the jurisdiction area. When the carrier control unit 41 allows the carrier 3 to pass through the merging section 21, it performs a blocking control to allow or prohibit the carrier 3 from passing through the merging section 21. Specifically, when the carrier control unit 41 receives a merging section passing permission request related to the merging section 21 from the carrier 3, if it has not set a merging closed area RG for the area including the merging section 21, it sends a merging section passing permission response to the carrier 3 and allows the carrier 3 to pass through the merging section 21. In this way, the carrier control unit 41 allows the carrier 3 to pass through and sets the merging closed area RG. The merging closed area RG is used to prohibit the carrier 3 that has not received the merging section passing permission response from entering the closed area (not shown) including the merging section 21. After the carrier 3 that has passed through the merging section 21 passes through the post-merging point, the carrier control unit 41 releases the merging closed area RG. The post-merging point is a point on the downstream side of the merging section 21 (a point on the track 2). The post-merging point is, for example, a position set based on a predetermined point marker located on the downstream side of the merging section 21. In this embodiment, the post-merging point is set as the point closest to the merging section 21 on the downstream side of the merging section 21 as the reference. When the carrier control unit 41 receives a merging section passing permission request related to the merging section 21 from the carrier 3, if the merging closed area RG is set, it does not send a merging section passing permission response to the carrier 3 and makes the carrier 3 wait at the stop point T. The transport vehicle control unit 41 executes either priority control or non-priority control. In priority control, the transport vehicle control unit 41 sets either the first path R1 or the second path R2 as the priority path. Priority control is a control that causes the transport vehicle 3 traveling on one of the first path R1 and the second path R2 set as the priority path to pass through the merging section 21 prior to the transport vehicle 3 traveling on the other path. The method by which the transport vehicle control unit 41 sets the priority path will be described later. Non-priority control is a control that causes the transport vehicle 3 to pass through the merging section 21 in a manner that does not distinguish between the transport vehicle 3 traveling on the first path R1 and the transport vehicle 3 traveling on the second path R2. The term "not distinguishing between" means, for example, not imposing a priority order on the transport vehicle 3 passing through the merging section 21. In other words, non-priority control equally determines whether to allow the transport vehicle 3 traveling on one of the first path R1 and the second path R2 and the transport vehicle 3 traveling on the other path to pass through the merging section 21 with respect to the path on which they are traveling. In the present embodiment, in non-priority control, the transport vehicle 3 traveling on the first path R1 and the transport vehicle 3 traveling on the second path R2 alternately pass through the merging section 21. Details of the priority control and the non-priority control will be described later. The congestion determination unit 42 determines whether congestion of the transport vehicle 3 has occurred in the predetermined determination target areas 61, 62 (see FIG. 1) located upstream of the merging section 21 in the first path R1 or the second path R2. In the present embodiment, each of the determination target areas 61, 62 (hereinafter, there are cases where it is referred to as the "determination target area") is set to a range within 15 m from the merging section 21 on the upstream side of the merging section 21. The determination target areas 61, 62 can be, for example, preset, or can be appropriately changed. The length of the determination target areas 61, 62 can be set, for example, based on the above-described predetermined distance used in the stop control performed by the travel control unit 33. The length of the determination target areas 61, 62 can be set to an integer multiple of the above-described predetermined distance, or can be set to a length obtained by adding the vehicle length of the transport vehicle 3 of a predetermined quantity (threshold value) described later to an integer multiple of the above-described predetermined distance. The determination target area 61 is set on the first path R1. The determination target area 61 includes the connecting path 51 and a plurality of merging paths 52 included in the first path R1. The determination target area 62 is set on the second path R2. The determination target area 62 includes a portion of the third straight path 29 included in the second path R2 that is located upstream of the merging section 21a. The clogging determination unit 42 determines whether a clogging of the carrier vehicle 3 has occurred in the determination target area. In the present embodiment, when there are a predetermined number or more of carrier vehicles 3 in the determination target area whose distance from the carrier vehicle 3 located in front of the own vehicle is equal to or less than a predetermined distance, the clogging determination unit 42 determines that a clogging of the carrier vehicle 3 has occurred in the determination target area. The predetermined number is, for example, a threshold value set in advance, and can be appropriately changed. When there are a predetermined number or more of carrier vehicles 3 that are stopped by the control of the travel control unit 33 in the determination target area, the clogging determination unit 42 determines that a clogging of the carrier vehicle 3 has occurred in the determination target area. The clogging determination unit 42 periodically determines, based on the status reports periodically sent from the travel control unit 33, whether there are a predetermined number or more of carrier vehicles 3 that are stopped by the control of the travel control unit 33 in the determination target area. Although the period is, for example, 10 seconds, it can also be appropriately changed. The period is, for example, set in advance. The clogging determination unit 42 performs the above-described clogging determination based on the position information included in the status report and the information indicating that the stop control is being executed. The control switching unit 43 switches the control executed by the carrier vehicle control unit 41 according to the determination result of the clogging determination unit 42. When it is determined by the clogging determination unit 42 that a clogging of the carrier vehicle 3 has occurred in the determination target area, the control switching unit 43 switches the control so that the carrier vehicle control unit 41 executes non-priority control. When it is determined by the clogging determination unit 42 that a clogging of the carrier vehicle 3 has not occurred in the determination target area, the control switching unit 43 switches the control so that the carrier vehicle control unit 41 executes priority control. Next, with reference to FIGS. 3 to 9, the operation of the conveying system 1 of the present embodiment will be described. In the state shown in FIG. 3, the case where the carrier vehicle control unit 41 executes non-priority control will be described. First, the clogging determination unit 42 determines whether a clogging of the carrier vehicle 3 has occurred in the determination target area. When there are a predetermined number (the above threshold value) or more of carrier vehicles 3 that are stopped by the control of the travel control unit 33 in the determination target area, the clogging determination unit 42 determines that a clogging of the carrier vehicle 3 has not occurred in the determination target area. In the examples shown in the figures after FIG. 3, the threshold value is set to 6 vehicles. In FIG. 3, the number of carrier vehicles 3 that are stopped by the control of the travel control unit 33 in the determination target area 61 is 3 vehicles. Also, the number of carrier vehicles 3 that are stopped by the control of the travel control unit 33 in the determination target area 62 is 2 vehicles. Therefore, as a result of the clogging determination unit 42 performing the above-described periodic clogging determination, the clogging determination unit 42 determines that a clogging of the carrier vehicle 3 has not occurred in the determination target area. Subsequently, the control switching unit 43 switches the control executed by the carrier control unit 41 according to the determination result of the blockage determination unit 42. Specifically, since the blockage determination unit 42 determines that there is no blockage of the carrier 3 in the determination target area, the control switching unit 43 switches the control so that the carrier control unit 41 executes priority control. Hereinafter, in the priority control, among the carriers 3 traveling on one of the first path R1 and the second path R2 and the carriers 3 traveling on the other, the carrier 3 that preferentially passes through the merging unit 21 is called the priority carrier 3a, and the carrier 3 traveling on the other is called the standby carrier 3b. In the first path R1 and the second path R2, the path on which the priority carrier 3a travels is called the "priority path", and the path on which the standby carrier 3b travels is called the "standby path". When the control switching unit 43 switches the control executed by the carrier control unit 41 from non-priority control to priority control, the carrier control unit 41 sets one of the first path R1 and the second path R2 as the priority path and the other as the standby path. For example, among the first path R1 and the second path R2, the carrier control unit 41 sets the one on which the carrier 3 that first receives the merging unit passage permission request from the control switching unit 43 travels as the priority path and the other as the standby path. Hereinafter, an example in which the carrier control unit 41 sets the first path R1 as the priority path and the second path R2 as the standby path will be described. As shown in FIG. 4, when the carrier control unit 41 receives a merging unit passage permission request from the priority carrier 3a, the carrier control unit 41 sends a merging unit passage permission response to the priority carrier 3a, allows the priority carrier 3a to pass, and sets the merging closed area RG. After the priority carrier 3a passes the merging point, the carrier control unit 41 releases the merging closed area RG. The control switching unit 43 switches the control, and from after receiving the merging unit passage permission request until a predetermined time has elapsed, the carrier control unit 41 repeatedly executes the same control. This predetermined time is set in advance, for example, and can be appropriately changed. The carrier control unit 41 does not send a merging unit passage permission response to the standby carrier 3b, but makes the standby carrier 3b wait at the stop point T until the predetermined time has elapsed. As a result, the priority carrier 3a traveling on the first path R1 continuously passes through the merging unit 21. At the time when the above-mentioned predetermined time has elapsed, the carrier control unit 41 sets the first path R1 set as the priority path as the standby path and sets the second path R2 set as the standby path as the priority path. The carrier control unit 41 repeatedly executes the above control. Thus, as shown in FIG. 5, the priority carrier 3a traveling on the second path R2 continuously passes through the merging unit 21. Each time the above-mentioned predetermined time elapses, the carrier control unit 41 alternately switches the priority path and the standby path. Next, the operation when a jam of the carrier vehicle 3 occurs in the determination target area will be described. In the state shown in FIG. 6, the case where priority control is executed on the carrier vehicle control unit 41 will be described. In FIG. 6, the number of carrier vehicles 3 that are stopped under the control of the travel control unit 33 in the determination target area 61 is six. Therefore, as a result of the congestion determination unit 42 performing the above-described periodic congestion determination, the congestion determination unit 42 determines that a congestion of the carrier vehicle 3 has occurred in the determination target area. Subsequently, since the congestion determination unit 42 determines that a congestion of the carrier vehicle 3 has occurred in the determination target area, the control switching unit 43 switches the control so that the carrier vehicle control unit 41 executes non-priority control. Hereinafter, in non-priority control, the carrier vehicle 3 that is located upstream of the confluence section 21 and is closest to the confluence section 21 on each of the first path R1 and the second path R2 is referred to as the foremost carrier vehicle 3c. When the control switching unit 43 switches the control executed by the carrier vehicle control unit 41 from priority control to non-priority control, the carrier vehicle control unit 41 sends a confluence section passage permission response to either the foremost carrier vehicle 3c on the first path R1 or the foremost carrier vehicle 3c on the second path R2. For example, the carrier vehicle control unit 41 sends a confluence section passage permission response to the foremost carrier vehicle 3c on the path set for the determination target area determined to be congested by the congestion determination unit 42 among the first path R1 and the second path R2. In the example of FIG. 6, an example in which the carrier vehicle control unit 41 sends a confluence section passage permission response to the foremost carrier vehicle 3c on the first path R1 when the control switching unit 43 switches the control will be described. As shown in FIG. 7, when the carrier vehicle control unit 41 receives a confluence section passage permission request from the foremost carrier vehicle 3c on the first path R1, the carrier vehicle control unit 41 sends a confluence section passage permission response to the foremost carrier vehicle 3c, permits the foremost carrier vehicle 3c to pass, and sets a confluence blocking area RG. After the foremost carrier vehicle 3c passes the confluence post point, the carrier vehicle control unit 41 releases the confluence blocking area RG. The carrier vehicle control unit 41 does not send a confluence section passage permission response to the foremost carrier vehicle 3c on the second path R2, and causes the foremost carrier vehicle 3c on the second path R2 to wait at the stop point T until the foremost carrier vehicle 3c on the first path R1 passes the confluence post point. Next, as shown in FIG. 8, when the carrier control unit 41 receives a confluence section passage permission request from the foremost carrier 3c on the second path R2, it sends a confluence section passage permission response to the foremost carrier 3c, allows the foremost carrier 3c to pass, and sets a confluence lock area RG. After the foremost carrier 3c passes the confluence point, the carrier control unit 41 releases the confluence lock area RG. The carrier control unit 41 does not send a confluence section passage permission response to the foremost carrier 3c on the first path R1, but makes the foremost carrier 3c on the first path R1 wait at the stop point T until the foremost carrier 3c on the second path R2 passes the confluence point. Next, as shown in FIG. 9, the carrier control unit 41 repeats the same process, whereby the foremost carrier 3c moving on the first path R1 and the foremost carrier 3c moving on the second path R2 can pass through the confluence section 21 one by one and alternately. In the conveying system 1 of the present embodiment, when the carrier control unit 41 included in the controller 4 determines that a blockage of the carrier 3 has occurred in the determination target area, it executes non-priority control. In non-priority control, the carrier 3 is not differentiated by the travel path on which the carrier 3 travels, and the carrier 3 passes through the confluence section 21, so that the blockage of the carrier 3 in the determination target area can be eliminated (see FIGS. 6 to 9). For example, when a severe blockage occurs in the determination target area, the control for allowing the carrier 3 to pass through the confluence section 21 can be automatically switched from priority control to non-priority control, so that the time for relieving the blockage can be shortened. Also, in order not to make the waiting time of the carrier 3 on the upstream side of the confluence section 21 too long, a limit may be considered for the waiting time, and DLE is executed when the waiting time exceeds a predetermined time. Even in this case, the waiting carrier 3 can move forward relatively early, so that the frequency of executing DLE can be reduced. Also, in the conveying system 1, when the carrier control unit 41 included in the controller 4 determines that no blockage of the carrier 3 has occurred in the determination target area, it executes priority control. In priority control, the carrier 3 moving on one of the first path R1 and the second path R2 set as the priority path passes through the confluence section 21 preferentially with respect to the carrier 3 moving on the other (see FIGS. 3 to 5). Thereby, when the carrier 3 on one side passes through the confluence section 21, it is not necessary to wait until the carrier 3 on the other side passes through the confluence section 21. As a result, the carrier 3 on one side can pass through the confluence section 21 without repeated starting and stopping. According to the above, the conveying efficiency can be improved. In non-priority control, the carrier vehicle 3 moving on the first path R1 and the carrier vehicle 3 moving on the second path R2 are alternately passed through the merging section 21 (refer to FIGS. 6 to 9). Thereby, by alternately passing the carrier vehicle 3 moving on the first path R1 and the carrier vehicle 3 moving on the second path R2 through the merging section 21, it is possible to surely eliminate the congestion of the carrier vehicle 3 in the determination target area. When there are a predetermined number or more of carrier vehicles 3 within a predetermined distance from the carrier vehicle 3 located in front of the own vehicle in the determination target area, the congestion determination unit 42 included in the controller 4 determines that congestion of the carrier vehicle 3 has occurred in the determination target area. Thereby, it is possible to determine the presence or absence of congestion of the carrier vehicle 3 based on the number of carrier vehicles 3 approaching each other in the determination target area (refer to FIG. 3). Thereby, it is possible to easily determine the congestion of the carrier vehicle 3 in the determination target area. The carrier vehicle 3 includes a measurement unit 32 that measures the distance to the carrier vehicle 3 located in front of the own vehicle, and a travel control unit 33 that stops the own vehicle when the distance is equal to or less than the predetermined distance. When there are a predetermined number or more of carrier vehicles 3 that are stopped under the control of the travel control unit 33 in the determination target area, the congestion determination unit 42 included in the controller 4 determines that congestion of the carrier vehicle 3 has occurred in the determination target area. In this case, it is possible to determine the presence or absence of congestion of the carrier vehicle 3 based on the number of carrier vehicles 3 that are stopped under the control of the travel control unit 33 in the determination target area (refer to FIG. 6). Thereby, it is possible to more easily determine the congestion of the carrier vehicle 3 in the determination target area. The determination target area 61 includes a connection path 51 that is connected to the merging section 21, and a plurality of merging paths 52 that merge into the connection path 51 (refer to FIG. 1). For example, when the connection path 51 does not have a sufficient length, it is difficult to determine the presence or absence of congestion only from the traveling state on the connection path 51. By considering not only the connection path 51 but also the number of carrier vehicles 3 on the plurality of merging paths 52, it is possible to correctly determine the presence or absence of congestion regardless of the layout of the travel path. As described above, although the embodiments of the present invention have been described, the present invention is not limited to the above embodiments. For example, in non-priority control, the carrier vehicle 3 moving on the first path R1 and the carrier vehicle 3 moving on the second path R2 may alternately pass through the merging section 21 in a predetermined number of two or more at a time. The predetermined number can be set in advance, for example, and can be appropriately changed. In this case, the carrier vehicle control unit 41 repeatedly executes control to pass the foremost carrier vehicle 3c on the first path R1 through the merging section 21, and after a predetermined number of carrier vehicles 3 have passed through the merging section 21, it is only necessary to repeatedly execute control to pass the foremost carrier vehicle 3c on the second path R2 through the merging section 21. Non-priority control only needs to be control that allows the transport vehicle 3 to pass through the merging section 21 in a way that does not distinguish between superiority and inferiority depending on whether the transport vehicle 3 travels on the first path R1 or the second path R2. As non-priority control, various controls can be adopted. In non-priority control, the transport vehicle control unit 41 can also, according to the transport instruction, give priority to the transport vehicle 3 that transports items to a specific transport destination to pass through the merging section 21 over the transport vehicle 3 that transports items to a transport destination other than the specific transport destination. In this case, for example, items can be quickly transported to a specific transport destination where the demand for items is higher than that for other transport destinations. In the above embodiment, at the time point after a predetermined time has elapsed since the transport vehicle control unit 41 switches the control and initially receives a merging section passage permission request, the first path R1 set as the priority path is set as the standby path, and the second path R2 set as the standby path is set as the priority path. However, the transport vehicle control unit 41 can also, at the time point when it determines that a predetermined condition (hereinafter referred to as the "switching condition") is satisfied, set the path set as the priority path as the standby path, and set the path set as the standby path as the priority path. Hereinafter, an example of the switching condition will be described. The switching condition includes, for example: after all the priority transport vehicles 3a that send a merging section passage permission request to the transport vehicle control unit 41 at a predetermined time point have passed through the merging point, and the merging closed area RG is released (hereinafter referred to as the "first condition"). The predetermined time point is, for example, set in advance and can be appropriately changed. As an example, the predetermined time point is the time point after a predetermined time has elapsed in a state where the transport vehicle control unit 41 has not received a new merging section passage permission request from the priority transport vehicle 3a. In this case, for example, the travel control unit 33 includes the identification information, which is the information uniquely specifying the vehicle itself, in the merging section passage permission request and sends it to the transport vehicle control unit 41. The transport vehicle control unit 41 specifies the priority transport vehicle 3a that sends a merging section passage permission request to the transport vehicle control unit 41 at the time point after the above-mentioned predetermined time has elapsed according to the identification information. When all the specified priority transport vehicles 3a have passed through the merging point and the merging closed area RG is released, the transport vehicle control unit 41 determines that the first condition is satisfied. The switching conditions include, for example, that the number of waiting carrier vehicles 3b that send a confluence section passage permission request to the carrier vehicle control unit 41 and wait at the stop point T is larger than a predetermined number (hereinafter referred to as "the second condition"). This predetermined number is, for example, set in advance and can be appropriately changed. As an example, this predetermined number is 3. In this case, for example, the carrier vehicle control unit 41 specifies the waiting carrier vehicles 3b that send a confluence section passage permission request to the carrier vehicle control unit 41 and wait at the stop point T based on the identification information. When the number of the specified waiting carrier vehicles 3b reaches the predetermined number and a new confluence section passage permission request is received from a waiting carrier vehicle 3b other than the specified waiting carrier vehicles 3b, the carrier vehicle control unit 41 determines that the second condition is satisfied. The switching conditions include, for example, that the control switching unit 43 switches the control and a predetermined time (hereinafter referred to as "the third condition") has elapsed after the carrier vehicle control unit 41 initially receives a confluence section passage permission request. In this case, when the control switching unit 43 switches the control and a predetermined time has elapsed after the carrier vehicle control unit 41 initially receives a confluence section passage permission request, the carrier vehicle control unit 41 determines that the third condition is satisfied. The carrier vehicle control unit 41 may, for example, also use the satisfaction of all of these first condition, second condition, and third condition as the switching condition. The carrier vehicle control unit 41 may, for example, also use only any one of the above first condition, second condition, and third condition as the switching condition. Also, the carrier vehicle control unit 41 may, for example, appropriately combine the above first condition, second condition, and third condition as the switching condition. In this case, for example, the carrier vehicle control unit 41 may determine that the switching condition is satisfied when it determines that any one of the above first condition, second condition, and third condition is satisfied, or may also determine that the switching condition is satisfied when it determines that any two or more of the above first condition, second condition, and third condition are satisfied. However, the content of the above switching condition is only an example and can be appropriately changed without departing from the gist of the present invention. Also, when using at least one of the second condition and the third condition as the switching condition, it may be set that even when the carrier vehicle control unit 41 determines that the second condition or the third condition is satisfied, the switching of the priority path and the waiting path is not performed until all the priority carrier vehicles 3a that send a confluence section passage permission response pass through the post-confluence point and the confluence closed area RG is set. In the above embodiment, the congestion determination unit 42 determines whether congestion of the carrier vehicles 3 occurs in the determination target areas 61 and 62. However, the congestion determination unit 42 may not determine whether congestion of the carrier vehicles 3 occurs in the determination target area where the priority path is set, but only determine whether congestion of the carrier vehicles 3 occurs in the determination target area set on the non-priority path. In the above-described embodiment, when the distance measured by the measurement unit 32 is equal to or less than a predetermined distance, the travel control unit 33 stops the host vehicle. However, the control is not limited thereto. When the distance measured by the measurement unit 32 is equal to or less than a predetermined distance (in the case where the two transfer vehicles 3 approach each other), the travel control unit 33 may also control the host vehicle (i.e., the rear transfer vehicle 3 among the two transfer vehicles 3) to travel (decelerate) at a very low travel speed. In this case, an emergency stop distance shorter than the predetermined distance may also be set. In the above-described embodiment, although the overhead traveling type unmanned transfer vehicle is used as the transfer vehicle 3, the transfer vehicle 3 is not particularly limited. The transfer vehicle 3 may also be an overhead traveling type transfer shuttle. The transfer vehicle 3 may also be a rail type unmanned transfer cart that can travel along a track on the floor. The transfer vehicle 3 may also be a magnetic guidance type unmanned transfer vehicle that can travel along a path formed by a magnetic tape or the like. The transfer vehicle 3 may also be a laser guidance type unmanned transfer cart that can travel along a determined path by laser light guidance. In the above-described embodiment, one or a plurality of other controllers for relaying between the controller 4 and the transfer vehicle 3 may also be provided. The constituent elements of the present invention can be described as follows. [1] A conveying system, comprising: a plurality of carrier vehicles that travel on a travel path and convey articles; and a controller that controls the travel of the plurality of carrier vehicles; the travel path has a first path, a second path different from the first path, and a confluence section where the first path and the second path merge; the controller executes either priority control or non-priority control, the priority control causes the carrier vehicle traveling on one of the first path and the second path set as the priority path to pass through the confluence section preferentially over the carrier vehicle traveling on the other path, the non-priority control causes the carrier vehicle to pass through the confluence section in a manner that does not distinguish between the carrier vehicle traveling on the first path and the carrier vehicle traveling on the second path, when a blockage of the carrier vehicle occurs in a predetermined determination target area upstream of the confluence section in the first path or the second path, the controller executes the non-priority control, when no blockage of the carrier vehicle occurs in the determination target area, the controller executes the priority control. [2] The conveying system according to [1], wherein, in the non-priority control, the carrier vehicle traveling on the first path and the carrier vehicle traveling on the second path alternately pass through the confluence section. [3] The conveying system according to [1] or [2], wherein the controller determines that a blockage of the carrier vehicle occurs in the determination target area when there are a predetermined number or more of the carrier vehicles in the determination target area whose distance from the carrier vehicle in front of the vehicle is equal to or less than a predetermined distance. [4] The conveying system according to [3], wherein the carrier vehicle has: a measuring unit that measures the distance from the carrier vehicle in front of the vehicle; and a travel control unit that stops the vehicle when the distance is equal to or less than the predetermined distance; the controller determines that a blockage of the carrier vehicle occurs in the determination target area when there are a predetermined number or more of the carrier vehicles that are being stopped by the control using the travel control unit in the determination target area. [5] The conveying system according to any one of [1] to [4], wherein the determination target area includes: a connecting path that is connected to the confluence section; and a plurality of confluence paths that merge into the connecting path. 1: Conveyor system 2: Track (travel path) 3: Conveyor vehicle 3a: Priority conveyor vehicle 3b: Conveyor vehicle to wait 3c: Frontmost conveyor vehicle 4: Controller 20: Path section 21: Merging section 21a: Merging section 21b: Merging section 22: Branching section 22a: Branching section 22b: Branching section 23: Straight path 24: Curved path 25: S-shaped path 26: U-shaped path 27: First straight path 28: Second straight path 29: Third straight path 31: Position acquisition unit 32: Measurement unit 33: Transition control unit 41: Conveyor vehicle control unit 42: Blockage determination unit 43: Control switching unit 51: Connection path 52: Merging path 61, 62: Determination target area R1: First path R2: Second path RG: Merging closed area T: Stop point FIG. 1 is an overall schematic diagram of a conveyor system according to an embodiment of the present invention. FIG. 2 is a block diagram showing the functional configuration of a controller and a conveyor vehicle according to an embodiment. FIG. 3 is a diagram showing one step in the operation of the conveyor system. FIG. 4 is a diagram showing the step after the step shown in FIG. 3. FIG. 5 is a diagram showing the step after the step shown in FIG. 4. FIG. 6 is a diagram showing the step after the step shown in FIG. 5. FIG. 7 is a diagram showing the step after the step shown in FIG. 6. FIG. 8 is a diagram showing the step after the step shown in FIG. 7. FIG. 9 is a diagram showing the step after the step shown in FIG. 8. 1: Conveyor system 2: Track (travel path) 3: Conveyor vehicle 4: Controller 20: Path section 21: Merging section 21a: Merging section 21b: Merging section 22: Branching section 22a: Branching section 22b: Branching section 23: Straight path 24: Curved path 25: S-shaped path 26: U-shaped path 27: First straight path 28: Second straight path 29: Third straight path 51: Connection path 52: Merging path 61, 62: Determination target area R1: First path R2: Second path RG: Merging closed area T: Stop point

Claims

1. A conveying system comprising: a plurality of conveyor vehicles that move and convey items along a conveying path; and a controller that controls the movement of the plurality of conveyor vehicles; the conveying path having a first path having a branch, a second path different from the first path, and a merging section where the first path and the second path merge downstream of the branch; the controller having a conveyor vehicle control unit that receives status information including the current position and status of the conveyor vehicle from the conveyor vehicle, and a congestion determination unit that determines whether a congestion has occurred in a target area based on the status information, and performing either priority control or non-priority control, wherein the priority control causes the conveyor vehicle moving along one of the first path and the second path, which are designated as priority paths, to pass through the merging section with priority over the conveyor vehicle moving along the other path. The aforementioned non-priority control allows the transport vehicle to pass through the merging section in a manner that does not prioritize the transport vehicle's movement on either the first or second path. When it is determined that a blockage of the transport vehicle occurs on the first path in a first target area that is upstream of the branch and closest to the stop point of the transport vehicle to the branch, or on the second path in a predetermined second target area that is upstream of the merging section, the controller executes the aforementioned non-priority control. When it is determined that no blockage of the transport vehicle occurs in the target area, the controller executes the aforementioned priority control.

2. As in request item 1, the conveying system, wherein, In the aforementioned non-priority control, the aforementioned transport vehicle traveling on the first path and the aforementioned transport vehicle traveling on the second path alternately pass through the aforementioned merging section.

3. As in request item 1 or 2, the conveying system, wherein, When the aforementioned blockage determination unit determines that a blockage of the aforementioned transport vehicle has occurred in the aforementioned blockage determination area when there are a predetermined number or more transport vehicles in the aforementioned determination target area that are at a predetermined distance or less from the aforementioned transport vehicle located in front of the vehicle.

4. As in request item 3, the conveying system, wherein, The aforementioned transport vehicle includes: a measuring unit that measures the distance to another transport vehicle located in front of the aforementioned main vehicle; and a movement control unit that stops the aforementioned main vehicle when the distance is less than a predetermined distance; and a blockage determination unit that determines that a blockage of the transport vehicles has occurred in the aforementioned target area when there are a predetermined number or more of the transport vehicles that are being stopped under the control of the aforementioned movement control unit.

5. As in request item 1 or 2, the conveying system, wherein, The aforementioned target area includes: a connecting path that is connected to the aforementioned merging section; and a plurality of merging paths that merge into the aforementioned connecting path.

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