Patent Publication Number: US-2021162850-A1

Title: Overhead traveling vehicle system

Description:
TECHNICAL FIELD 
     This disclosure relates to an overhead traveling vehicle system. 
     BACKGROUND 
     In semiconductor manufacturing factories, an overhead traveling vehicle system is used to transport articles such as FOUPs containing semiconductor wafers and reticle pods containing reticles. In such an overhead traveling vehicle system, it is proposed to mount on an overhead traveling vehicle a battery for traveling driving and to provide a charging facility that charges the battery while the overhead traveling vehicle, which travels on the track, is in a stop state (see Japanese Patent No. 5698497). In the overhead traveling vehicle system of JP &#39;497, the battery is charged by lowering terminals of the charging facility arranged above charging electrodes that are arranged above the traveling wheels in the overhead traveling vehicle, and bringing the terminals into contact with the charging electrodes. 
     In the overhead traveling vehicle system of JP &#39;497, the terminals of the charging facility are lowered and brought into contact with the charging electrodes above the traveling wheel and, therefore, the charging facility needs to be arranged above the track. Therefore, a space to arrange the charging facility is needed above the track, and the track needs to be arranged away (lowered) from the ceiling to allow the space. Since the overhead traveling vehicle has a main body suspended below the track from the traveling wheels, a movement space for the main body is required below the track. As a result, when the track is arranged away from the ceiling, the space for installing (the height dimension that allows installation of) various types of processing devices or storage devices is reduced within the building, creating a problem of the reduced efficiency of space utilization within the building. 
     It could therefore be helpful to provide an overhead traveling vehicle system capable of suppressing a reduction in the efficiency of space utilization within a building by enabling arrangement of the track for overhead traveling vehicles in the vicinity of the ceiling. 
     SUMMARY 
     Our overhead traveling vehicle system has an overhead traveling vehicle comprising a main body, at least an upper surface of which is of a rectangular shape as viewed in a plan view, and a traveling wheel which is provided in each of four corners on the upper surface of the main body and rolls on a traveling surface of a track, the main body being arranged below the track by connectors each extending downward from the traveling wheel, wherein the overhead traveling vehicle includes charging electrodes on the upper surface of the main body, and a charger is arranged in a space above the traveling surface, at least a part of which overlaps with a movement space for the traveling wheels as viewed in a side view, and does not overlap with the movement space as viewed in a plan view. 
     The track may include a first track provided along a first direction and a second track provided along a second direction intersecting with the first direction, the overhead traveling vehicle may be able to travel, moving from the first track to the second track, or from the second track to the first track, and the charger may be arranged at an intersection of the first track and the second track. The track may be a grid-patterned track in which a plurality of the first tracks and a plurality of the second tracks orthogonally intersect with each other and a plurality of cells are adjacent to each other as viewed in a plan view, the charger may include at least a power supply unit and a terminal unit, and the power supply unit and the terminal unit may be each arranged in a manner of being distributed to adjacent cells. The first tracks and the second tracks may be both provided along the same or substantially the same horizontal plane. 
     The terminal unit may be able to be raised or lowered between a connection position to be in contact with the charging electrodes and a waiting position to be away from the charging electrodes. The charger may include a control unit that controls the power supply unit and the terminal unit, and the control unit may be arranged in a cell different from the cells in which the power supply unit and the terminal unit are arranged. The power supply unit, the terminal unit, and the control unit may be electrically connected to each other by wiring, and the wiring may be arranged above the movement space. The overhead traveling vehicle may include a steerer that causes the traveling wheel to pivot around an axis in the vertical direction, and the charger may be arranged in a space that does not overlap with a pivoting space of the traveling wheel as viewed in a plan view. The charging electrodes may be arranged in a portion that does not overlap with a pivoting space of the steerer as viewed in a plan view. 
     The charger is arranged in a space, at least a part of which overlaps with the movement space for the traveling wheels as viewed in a side view, and does not overlap with the movement space for the traveling wheels as viewed in a plan view. Therefore, while preventing the traveling wheels from interfering with the charger, it is possible to suppress the space for arranging the charger above the track. As a result, the track can be arranged in the vicinity of the ceiling, and it is therefore possible to suppress a reduction in the efficiency of space utilization in the building. 
     In the configuration such that the track includes a first track provided along a first direction and a second track provided along a second direction intersecting with the first direction, the overhead traveling vehicle can travel, moving from the first track to the second track, or from the second track to the first track, and the charger is arranged at an intersection of the first track and the second track since the charger is arranged at the intersection, both the overhead traveling vehicle traveling on the first track and the overhead traveling vehicle traveling on the second track can easily access the charger. In the configuration such that the track is a grid-patterned track in which a plurality of the first tracks and a plurality of the second tracks orthogonally intersect with each other and a plurality of cells are adjacent to each other as viewed in a plan view, the charger includes at least a power supply unit and a terminal unit, the power supply unit and the terminal unit are each arranged in a manner of being distributed to adjacent cells, and the power supply unit and the terminal unit of the charger are arranged distributed in separate cells. As a result, the height-wise dimension of each unit can be reduced, and the space for arranging the units in the charger can be reduced in the vertical direction. In the configuration such that the first tracks and the second tracks are both provided along the same or substantially the same horizontal plane, both the first tracks and the second tracks can be arranged in the vicinity of the ceiling while also allowing the charger to be arranged. 
     In the configuration such that the terminal unit can be raised or lowered between a connection position to be in contact with the charging electrodes and a waiting position to be away from the charging electrodes, it is possible, by having the terminal unit at a waiting position when not charging, to prevent interference with the terminal unit when the overhead traveling vehicle is traveling. In the configuration such that the charger includes a control unit which controls the power supply unit and the terminal unit, and the control unit is arranged in a cell different from the cells in which the power supply unit and the terminal unit are arranged since the control unit is arranged in a separate cell, the height-wise dimension of each unit can be further reduced, and the space for arranging the control unit in the charger can be further reduced in the vertical direction. In the configuration such that the power supply unit, the terminal unit, and the control unit are electrically connected to each other by wiring, and the wiring is arranged above the movement space, it is possible to reliably prevent the traveling wheels from interfering with the wiring when the overhead traveling vehicle is traveling. In the configuration such that the overhead traveling vehicle includes a steerer that causes the traveling wheel to pivot around an axis in the vertical direction, and the charger is arranged in a space which does not overlap with a pivoting space of the traveling wheel as viewed in a plan view, it is possible to prevent the traveling wheel from interfering with the charger when the overhead traveling vehicle drives the steerer. In the configuration such that the charging electrodes are arranged in a portion which does not overlap with the pivoting space of the steerer as viewed in a plan view, it is possible to prevent the steerer from interfering with the charging electrodes when the steerer is driven. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an example of an overhead traveling vehicle system according to an example. 
         FIG. 2  is a plan view of the overhead traveling vehicle system shown in  FIG. 1 . 
         FIG. 3  is a side view of the overhead traveling vehicle system shown in  FIG. 1 . 
         FIG. 4  is a perspective view showing an example of an overhead traveling vehicle. 
         FIG. 5  is a front view of the overhead traveling vehicle shown in  FIG. 4 . 
         FIG. 6  is a plan view of the overhead traveling vehicle shown in  FIG. 4 . 
         FIG. 7  is a plan view showing the overhead traveling vehicle in one cell of a grid-patterned track. 
         FIG. 8  is a diagram showing an example of a connection configuration between units in a charger. 
         FIG. 9  is a diagram showing an example of a terminal unit. 
         FIG. 10  shows an example of when the overhead traveling vehicle travels along first tracks,  FIG. 10(A)  being a diagram of the overhead traveling vehicle in a state of traveling toward the terminal unit, and  FIG. 10(B)  being a diagram of the overhead traveling vehicle in a state of having reached below the terminal unit. 
         FIG. 11  shows an example of when the overhead traveling vehicle travels along second tracks,  FIG. 11(A)  being a diagram of the overhead traveling vehicle in a state of traveling toward the terminal unit, and  FIG. 11(B)  being a diagram of the overhead traveling vehicle in a state of having reached below the terminal unit. 
         FIG. 12  shows an example of an operation of the terminal unit,  FIG. 12(A)  being a diagram of terminals of the terminal unit in a state of having separated from charging electrodes, and  FIG. 12(B)  being a diagram of the terminals of the terminal unit in a state of having come into contact with the charging electrodes. 
     
    
    
     DESCRIPTION OF REFERENCE SIGNS 
     
         
         AX Pivot axis 
         C Cell 
         K 1  Movement space 
         K 2 , K 3  Pivoting space 
         M Article 
         P 1  Connection position 
         P 2  Waiting position 
         R Grid-patterned track (track) 
         R 1  First track 
         R 2  Second track 
         R 3  Partial track 
         R 1   a , R 2   a , R 3   a  Traveling surface 
         S 1 , S 2 , S 3  Space 
         SYS Overhead traveling vehicle system 
           10  Main body 
           10   a  Upper surface 
           16  Battery 
           17  Charging electrode 
           20  Traveler 
           30  Coupler 
           34  Steerer 
           40  Controller 
           50  Charger 
           51  Power supply unit 
           52  Terminal unit 
           52   b  Terminal 
           53  Control unit 
           54  Wiring 
           100  Overhead traveling vehicle 
       
    
     DETAILED DESCRIPTION 
     The following describes an example of our systems with reference to the drawings. However, this disclosure is not limited to the example. In the drawings, scale is changed as necessary to illustrate the example such as by enlarging or emphasizing a part. In the following drawings, an XYZ coordinate system is used to describe the directions in each drawing. In this XYZ coordinate system, a plane parallel to the horizontal plane is defined as an XY plane. On this XY plane, one linear direction, which is the traveling direction of the overhead traveling vehicle  100 , is referred to as the X direction, and the direction orthogonal to the X direction is referred to as the Y direction. The traveling direction of the overhead traveling vehicle  100  can change from the state shown in the following figure to another direction, and may also travel along, for example, a curved direction in some instances. The direction perpendicular to the XY plane is referred to as the Z direction. For each of the X direction, the Y direction, and the Z direction, description is made with a definition in which a direction indicated by an arrow is the positive (+) direction and a direction opposite to the direction indicated by the arrow is the negative (−) direction. The rotational direction about the Z axis is referred to as the OZ direction. 
       FIG. 1  is a perspective view showing an example of an overhead traveling vehicle system SYS.  FIG. 2  is a plan view of the overhead traveling vehicle system SYS shown in  FIG. 1 .  FIG. 3  is a side view of the overhead traveling vehicle system SYS shown in  FIG. 1 . The overhead traveling vehicle system SYS shown in  FIG. 1  to  FIG. 3  is a system to transport articles M such as FOUPs containing semiconductor wafers and reticle pods containing reticles in a clean room of a semiconductor manufacturing factory, for example. The overhead traveling vehicle system SYS includes a grid-patterned track R, an overhead traveling vehicle  100 , and a charger  50 . 
     The grid-patterned track R is a form of track. The grid-patterned track R is installed in the vicinity of a ceiling T (see  FIG. 3 ) of a clean room. The grid-patterned track R has first tracks R 1 , second tracks R 2 , and partial tracks R 3 . The grid-patterned track R is provided in a state of being suspended from the ceiling T via the suspenders H. Each suspender H has first portions H 1  to suspend the first track R 1 , second portions H 2  to suspend the second track R 2 , and a third portion H 3  to suspend the partial track R 3 . The first portion H 1  and the second portion H 2  are each provided at two opposing locations with the third portion H 3  therebetween. 
     A plurality of the first tracks R 1  are provided along the X direction (the first direction). A plurality of the second tracks R 2  are provided along the Y direction (the second direction). In this example, the first direction, along which the first tracks R 1  are provided, and the second direction, along which the second tracks R 2  are provided, orthogonally intersect with each other. The partial track R 3  is arranged at a portion where the first track R 1  and the second track R 2  intersect with each other. Between the first track R 1  and the partial track R 3  and between the second track R 2  and the partial track R 3 , there is provided a clearance D. In the grid-patterned track R, the first tracks R 1  and the second tracks R 2  orthogonally intersect with each other, thereby establishing a state where a plurality of cells C are adjacent to each other as viewed in a plan view. A single cell C is a region or a space surrounded by two first tracks R 1  adjacent to each other in the Y direction and two second tracks R 2  adjacent to each other in the X direction. 
     The first track R 1 , the second track R 2 , and the partial track R 3  respectively have traveling surfaces R 1   a , R 2   a , and R 3   a  on which the traveling wheels  21  described later of the overhead traveling vehicle  100  travel. The clearance D between the first track R 1  and the partial track R 3  and the clearance D between the second track R 2  and the partial track R 3  are potions over which couplers  30  (to be described later) serving as part of the overhead traveling vehicle  100  travel when the overhead traveling vehicle  100  having traveled on the first track R 1  crosses the second track R 2  or when the overhead traveling vehicle  100  having traveled on the second track R 2  crosses the first track R 1 . Therefore, the clearance D is provided with a width that allows the coupler  30  to travel thereover. The first tracks R 1 , the second tracks R 2 , and the partial tracks R 3  are provided along the same or substantially the same horizontal plane. The first tracks R 1 , the second tracks R 2 , and the partial tracks R 3  are such that the traveling surfaces R 1   a , R 2   a , and R 3   a  thereof are arranged on the same or substantially the same horizontal plane. 
     The charger  50  supplies electric power to a battery  16  of the overhead traveling vehicle  100 , which will be described later. The charger  50  is arranged in a space S 1  which is above the traveling surfaces R 1   a , R 2   a , and R 3   a  of the grid-patterned track R, at least a part of which overlaps with a movement space K 1  for the traveling wheels  21  of the overhead traveling vehicle  100  (to be described later) as viewed in a side view ( FIG. 3 ), and does not overlap with the movement space K 1  as viewed in a plan view ( FIG. 2 ). The charger  50  includes a power supply unit  51 , a terminal unit  52 , and two control units  53 . 
     The power supply unit  51  is supported by a frame  51   a . The frame  51   a  is fixed to one or both of the first track R 1  and the second track R 2 . However, the frame  51   a  is not limited to this configuration, and may be suspended from the ceiling T, for example. The terminal unit  52  is supported by a frame  52   a . The frame  52   a  is fixed to the first track R 1 . However, the frame  52   a  is not limited to this configuration, and may be fixed to the second track R 2  or suspended from the ceiling T. The control units  53  are supported by a frame  53   a . The frame  51   a  is fixed to one or both of the first track R 1  and the second track R 2 . However, the frame  51   a  is not limited to this configuration, and may be suspended from the ceiling T, for example. The details of the charger  50  will be described later. 
       FIG. 4  is a perspective view showing an example of the overhead traveling vehicle  100 .  FIG. 5  is a front view of the overhead traveling vehicle  100  shown in  FIG. 4 . As shown in  FIGS. 4 and 5 , the overhead traveling vehicle  100  has a main body  10 , travelers  20 , couplers  30 , and a controller  40 . The overhead traveling vehicle  100  moves along the grid-patterned track R and transports articles M such as FOUPs and reticle pods. A plurality of the overhead traveling vehicles  100  may be used in the grid-patterned track R, or one overhead traveling vehicle  100  may be used. By transporting articles M by a plurality of the overhead traveling vehicles  100 , it is possible to improve the efficiency of transporting articles M. 
     The main body  10  is arranged below the grid-patterned track R (on the −Z side). The main body  10  is formed, for example, in a rectangular shape as viewed in a plan view. Therefore, an upper surface  10   a  of the main body  10  has a rectangular shape and has four corners. The main body  10  is formed in a size that fits in a single cell C within the grid-patterned track R as viewed in a plan view. Therefore, the overhead traveling vehicles  100  traveling adjacent to each other on the grid-patterned track R do not interfere with one another. 
     The main body  10  has an article holder  13  to hold an article M, a lift driver  14  to raise or lower the article holder  13  in the vertical direction, and a lateral extender  11  to move the lift driver  14 . The article holder  13  suspends and holds an article M by grasping a flange Ma provided on the upper part of the article M. The article holder  13  is, for example, a chuck having claws  13   a  movable in the horizontal direction, and it inserts the claws  13   a  under the flange Ma of an article M and raises the article holder  13  to thereby suspend and hold the article M. The article holder  13  is connected to the lower end of suspenders  13   b  such as wires and belts. 
     The lift driver  14  is, for example, a hoist, and lowers the article holder  13  by feeding out the suspenders  13   b  and lifts the article holder  13  by taking up the suspenders  13   b . The lift driver  14  is controlled by the controller  40  to raise or lower the article holder  13  at a predetermined speed. Also, the lift driver  14  is controlled by the controller  40  to maintain the article holder  13  at a target height. The lateral extender  11  has a plurality of movable plates arranged in a stacked manner, for example, in the Z direction. The movable plates can move in the Y direction. The lift driver  14  is mounted on the lowermost movable plate. The lateral extender  11  can, by moving the movable plates by a driver not shown in the drawings, extend laterally with respect to the traveling direction the lift driver  14  attached to the lowermost movable plate and the article holder  13 . 
     The rotator  12  has a rotation member  12   a  and a rotation driver  12   b . The rotation member  12   a  is provided to be rotatable in an axial direction about the Z axis. The rotation member  12   a  supports the lateral extender  11 . An electric motor or the like is used for the rotation driver  12   b  and causes the rotation member  12   a  to rotate in the axial direction about the Z direction axis. The rotator  12  can, by rotating the rotation member  12   a  by the driving force from the rotation driver  12   b , rotate the lateral extender  11  (the lift driver  14  and the article holder  13 ) in the axial direction about the Z direction axis. In addition to the rotator  12  to control the direction of laterally extending the lift driver  14  and the article holder  13 , a rotator to control the attitude of the lift driver  14  and the article holder  13  within the horizontal plane may be further provided between the lateral extender  11  and the lift driver  14 . 
     The main body  10  includes a battery  16  and charging electrodes  17 . The battery  16  is arranged inside the main body  10 . The battery  16  stores electric power to be supplied to the travelers  20 , the rotation driver  12   b , the lift driver  14  and so forth of the overhead traveling vehicle  100 . A secondary battery such as a lithium ion battery is used for the battery  16 . The capacity of the battery  16  is determined on the basis of electric power used in the overhead traveling vehicle  100 , operating time and so forth. The charging electrodes  17  are held by a holder  18  and are arranged on the upper surface  10   a  of the main body  10 . The charging electrodes  17  are provided side by side at two locations on the upper surface side of the holder  18 . One of the two charging electrodes  17  is electrically connected to the + side terminal of the battery  16 . The other charging electrode  17  is electrically connected to the − side terminal of the battery  16 . The battery  16  is supplied with electric power from the charger  50  via the charging electrodes  17 . 
     Each traveler  20  has a traveling wheel  21  and auxiliary wheels  22 . The traveling wheel  21  is arranged in each of the four corners on the upper surface  10   a  of the main body  10 . Each traveling wheel  21  is rotatably supported on the coupler  30  by a rotation shaft not shown in the drawings. This rotation shaft is provided in parallel or substantially parallel along the XY plane (the horizontal plane). Therefore, the traveling wheel  21  can rotate about the axis line of the rotation shaft along the horizontal direction. Each traveling wheel  21  is driven to rotate by the driving force of a traveling driver  33 , which will be described later. Each traveling wheel  21  rolls on the traveling surfaces R 1   a , R 2   a , and R 3   a  of the first track R 1 , the second track R 2 , and the partial track R 3  on the grid-patterned track R, causing the overhead traveling vehicle  100  to travel. The configuration is not limited to driving all of the four traveling wheels  21  to rotate by the drive force of the traveling driver  33 , and only some of the four traveling wheels  21  may be driven to rotate. 
     As shown in  FIG. 3 , the movement space K 1  for the traveling wheels  21  to move therein is formed on the traveling surfaces R 1   a , R 2   a , and R 3   a  of the first track R 1  and the second track R 2 . The height-wise (the Z direction) dimension of the movement space K 1  is the same as or substantially the same as the outer diameter of the traveling wheel  21 . Each traveling wheel  21  is provided to be able to pivot in the OZ direction about the pivot axis AX along the Z direction. The traveling wheel  21  can, by pivoting in the OZ direction, change the traveling direction thereof from the first direction to the second direction or from the second direction to the first direction. 
     The auxiliary wheels  22  are each arranged in front and rear of the traveling wheel  21  in the traveling direction. As with the traveling wheel  21 , each auxiliary wheel  22  can rotate about the axis line of the rotation axis thereof parallel or substantially parallel along the XY plane. The lower end of the auxiliary wheel  22  is set higher than the lower end of the traveling wheel  21 . Therefore, when the traveling wheel  21  is traveling on the traveling surfaces R 1   a , R 2   a , and R 3   a , the auxiliary wheel  22  does not come into contact with the traveling surfaces R 1   a , R 2   a , and R 3 . When the traveling wheel  21  passes over the clearance D, the auxiliary wheels  22  come into contact with the traveling surfaces R 1   a , R 2   a , and R 3  to prevent the traveling wheel  21  from falling. The configuration is not limited to providing two of the auxiliary wheels  22  for a single traveling wheel  21  and, for example, a single auxiliary wheel  22  may be provided for a single traveling wheel  21 , or no auxiliary wheel  22  may be provided. 
     The coupler  30  connects the main body  10  and the traveler  20 . The coupler  30  is provided at each of the four corners on the upper surface  10   a  of the main body  10 . The main body  10  is suspended by the couplers  30  and arranged below the grid-patterned track R. Each coupler  30  has a supporter  31  and a connector  32 . The supporter  31  rotatably supports the rotation shaft of the traveling wheel  21  and the rotation shafts of the auxiliary wheels  22 . The supporter  31  maintains the relative position between the traveling wheel  21  and the auxiliary wheels  22 . 
     The connector  32  extends downward from each supporter  31  and is coupled to the upper surface  10   a  of the main body  10  to hold the main body  10 . The connector  32  includes a transmission therein to transmit the driving force of the traveling driver  33  (to be described later) to the traveling wheel  21 . This transmission may be of a configuration with use of a chain or a belt, or a configuration with use of a gear train. The connector  32  is provided to be rotatable in the OZ direction about the pivot axis AX. Rotation of the connector  32  about the pivot axis AX can cause the traveling wheel  21  to pivot in the OZ direction. 
     The traveling driver  33  and the steerer  34  are provided in the coupler  30 . The traveling driver  33  is attached to the connector  32 . The traveling driver  33  is a drive source to drive the traveling wheel  21  and, for example, an electric motor or the like is used therefor. Each of the four traveling wheels  21  is driven by the traveling driver  33  to serve as a driving wheel. The four traveling wheels  21  are controlled by the controller  40  to have the same or substantially the same rotation speed. 
     The steerer  34  causes the connector  32  of the coupler  30  to rotate about the pivot axis AX to thereby cause the traveling wheel  21  to pivot in the OZ direction. The traveling direction of the overhead traveling vehicle  100  can be changed from the first direction to the second direction or from the second direction to the first direction, by causing the traveling wheel  21  to pivot in the OZ direction. 
     The steerer  34  has a drive source  35 , a pinion gear  36 , and a rack (a toothed rail)  37 . The drive source  35  is attached to a side surface of the traveling driver  33  away from the pivot axis AX. As the drive source  35 , for example, an electric motor or the like is used. The pinion gear  36  is attached to the lower surface side of the drive source  35 , and is driven to rotate in the OZ direction by the driving force generated by the drive source  35 . The pinion gear  36  is of a circular shape as viewed in a plan view and has a plurality of teeth  36   a  on the outer circumference thereof along the circumferential direction (see  FIG. 6 ). The rack  37  is fixed to the upper surface  10   a  of the main body  10 . The rack  37  is provided at each of the four corners on the upper surface  10   a  of the main body  10 , and is provided having an arc shape centered on the pivot axis AX of the traveling wheel  21 . The rack  37  has a plurality of teeth  37   a  which mesh with the teeth  36   a  of the pinion gear  36  on the outer circumference thereof along the circumferential direction. 
     The pinion gear  36  and the rack  37  are arranged in the state where the plurality of teeth  36   a  and the plurality of teeth  37   a  are in mesh with each other. As the pinion gear  36  rotates in the OZ direction, the pinion gear  36  moves in the circumferential direction about the pivot axis AX along the outer circumference of the rack  37 . This movement of the pinion gear  36  causes the traveling driver  33  and the steerer  34  to pivot together with the pinion gear  36  in the circumferential direction about the pivot axis AX. 
       FIG. 6  is a plan view showing an example of the upper surface side of the main body  10 . As shown in  FIG. 6 , the steerer  34  pivots in a pivoting space K 2  centered on the pivot axis AX as viewed in a plan view. Although the pivoting space K 2  of the top-right steerer  34  is shown with a hatched pattern as an example in  FIG. 6 , the pivoting space K 2  is formed at each of the four corners. As shown in  FIG. 6 , a space S 2  not overlapping with the pivoting space K 2  as viewed in a plan view is present on the upper surface  10   a  of the main body  10 . When the steerers  34  pivot, this space S 2  is a space which does not interfere with the steerers  34  pivoting. As shown in  FIG. 6 , the charging electrodes  17  are arranged in the space S 2 . This configuration can prevent the charging electrodes  17  from interfering with the steerers  34  even when the steerers  34  are pivoting. 
     As the steerers  34  pivot, the traveling wheel  21  and the auxiliary wheels  22  arranged in each of the four corners on the upper surface  10   a  all pivot in the OZ direction about the pivot axis AX within the range of 90 degrees. The driving of the steerers  34  is controlled by the controller  40 . The controller  40  may instruct the four traveling wheels  21  to perform the pivoting operation at the same timing, or may instruct them to perform the pivoting operations at different timings. By causing the traveling wheel  21  and the auxiliary wheels  22  to pivot, the traveling wheel  21  shifts from the state of being in contact with one of the first track R 1  and the second track R 2  to the state of being in contact with the other. As a result, the traveling direction of the overhead traveling vehicle  100  can be switched between the first direction (the X direction) and the second direction (the Y direction). 
       FIG. 7  is a plan view of one of the cells C of the grid-patterned track R. As shown in  FIG. 7 , as the steerer  34  pivots, the traveling wheel  21  pivots within the range of a pivoting space K 3  centered on the pivot axis AX. The pivoting space K 3  is formed in a range of 90 degrees in the OZ direction from the first track R 1  to the second track R 2 . As shown in  FIG. 7 , a space S 3  not overlapping with the pivoting space K 3  as viewed in a plan view is present in the cell C. When the traveling wheel  21  pivots, this space S 3  is a space which does not interfere with the traveling wheel  21  pivoting. The space S 3  is formed within the space S 1  shown in  FIGS. 2 and 3 . 
     Electric power is supplied to the traveling drivers  33  and the steerers  34  from the battery  16  of the main body  10 . The controller  40  controls the operations of the traveling drivers  33  and the steerers  34 . The controller  40  controls the four traveling drivers  33  to set the speed, stop position, and so forth of the overhead traveling vehicle  100 , and controls the steerer  34  to shift from the first track R 1  to the second track R 2 , or from the second track R 2  to the first track R 1 . The controller  40  is provided in a part of the main body  10 , however, is not limited to this form. The controller  40  may be provided outside the main body  10 , for example. Electric power for the controller  40  is supplied from the battery  16 . 
     As shown in  FIGS. 2 and 3 , the power supply unit  51 , the terminal unit  52 , and the control units  53  of the charger  50  are arranged in the space S 1  at least a part of which overlaps with the movement space K 1  of the traveling wheels  21  as viewed in a side view, and does not overlap with the movement space K 1  as viewed in the plan view. The charger  50  is arranged at the intersection of the first tracks R 1  and the second tracks R 2 . As a result, both an overhead traveling vehicle  100  traveling on the first tracks R 1  and an overhead traveling vehicle  100  traveling on the second tracks R 2  can easily access the charger  50 . In the grid-patterned track R of this example, the overhead traveling vehicle  100  can enter each cell C from both the first tracks R 1  and the second tracks R 2 . Therefore, in this grid-patterned track R, each cell C serves as an intersection. 
     The power supply unit  51 , the terminal unit  52 , and the control units  53  are arranged distributed in different cells C. By distributing and arranging each unit in a separate cell C, the height-wise dimension of each unit can be reduced, and the space for arranging the units in the charger  50  can be reduced in the vertical direction. The power supply unit  51  and the terminal unit  52  are arranged distributed in adjacent cells C. This configuration enables a reduction in the length of wirings connecting the power supply unit  51  and the terminal unit  52 . 
     As shown in  FIG. 7 , the power supply unit  51 , the terminal unit  52 , and the control units  53  are arranged to fit in the space S 3 . This configuration can prevent the traveling wheels  21  from interfering with the power supply unit  51  and so forth when the traveling wheels  21  pivot although a part of the charger  50  partially overlaps with the movement space K 1  of the traveling wheels  21  as viewed in a side view. 
     The power supply unit  51  is connected to an external alternating current power source by wiring or the like, and makes adjustments such as conversion from alternating current to direct current and voltage setting, necessary for charging the battery  16 . A single power supply unit  51  is used in this example, however, our systems are not limited to this configuration and two or more power supply units may be used. When a plurality of power supply units  51  are used, each power supply unit  51  may be arranged in a different cell C. The control units  53  control the operations of the power supply unit  51  and the terminal unit  52  described later. In this example, two control units  53  are used, however, the number of control units  53  may be one, or three or more. These units are electrically connected by wiring. 
       FIG. 8  is a diagram showing an example of a connection configuration between the units in the charger  50 . As shown in  FIG. 8 , the power supply unit  51  and the control unit  53  are electrically connected by wirings  54 . The wiring  54  need to be arranged to cross the first track R 1  or the second track R 2 . For this reason, as shown in  FIG. 8 , a part of the wiring  54  is held by a stay  55  attached to a center rib (the portion extending upward from the traveling surface) of the second track R 2  (or the first track R 1 ). As a result, the wiring  54  is arranged above the movement space K 1  of the overhead traveling vehicle  100 . This configuration can prevent the traveling wheels  21  from interfering with the wiring  54  when the overhead traveling vehicle  100  is traveling. 
     The power supply unit  51  and the terminal unit  52  are also electrically connected by wiring  54 . This wiring  54  also crosses the first track R 1  or the second track R 2  as with the wiring  54  between the power supply unit  51  and the control unit  53  and, therefore, this wiring  54  is arranged above the movement space K 1  using a stay  55  shown in  FIG. 8 . 
       FIG. 9  is a diagram showing an example of the terminal unit  52 . The terminal unit  52  comes in contact with the charging electrodes  17  of the overhead traveling vehicle  100  to electrically connect to the charging electrodes  17 , and supplies electric power from the power supply unit  51  to the battery  16  via the charging electrodes  17 . As shown in  FIG. 9 , the terminal unit  52  includes terminals  52   b  that come into contact with the charging electrodes  17 , a holder  52   c  that holds the terminals  52   b , an elevator  52   d  that raises or lowers the holder  52   c  in the Z direction, and a supporting part  52   e  that supports the wiring  54  between the terminals  52   b  and the power supply unit  51 . 
     The terminals  52   b  are arranged oriented downward (in the −Z direction). Two terminals  52   b  are provided side by side to align with the two charging electrodes  17 , and are arranged at the same pitch as the two charging electrodes  17 . The holder  52   c  holds the upper parts of the terminals  52   b  while exposing the lower parts of the terminals  52   b . The elevator  52   d  is provided on the frame  52   a  and has a drive source such as an electric motor not shown in the drawings, and raises or lowers the holder  52   c  by the driving force of the drive source. The elevator  52   d  can raise or lower the holder  52   c  between a connection position P 1  at which the terminals  52   b  contact the charging electrodes  17  and a waiting position P 2  at which the terminals  52   b  are away from the charging electrodes  17 . This configuration can prevent interference between the charging electrodes  17  and the terminals  52   b  when the overhead traveling vehicle  100  is traveling as the terminals  52   b  (the holder  52   c ) retreat to the waiting position P 2  when charging is not performed. 
     The supporting part  52   e  is attached to the frame  52   a  and supports a part of the wiring  54 . When the wiring  54  is of a length required for raising and lowering the holder  52   c , the wiring  54  may sag down in the cell C in some situations. With the supporting part  52   e  having a part of the wiring  54  at a height near the frame  52   a , it is possible to prevent interference between a part of the overhead traveling vehicle  100  and the wiring  54  when the overhead traveling vehicle  100  is traveling. 
     Next, here are described operations performed when the overhead traveling vehicle  100  performs charging by the charger  50  in the overhead traveling vehicle system SYS.  FIG. 10  shows an example of when the overhead traveling vehicle  100  travels along the first tracks R 1 ,  FIG. 10(A)  being a diagram showing the overhead traveling vehicle  100  in a state of traveling toward the terminal unit  52 , and  FIG. 10(B)  being a diagram showing the overhead traveling vehicle  100  in a state of having reached below the terminal unit  52 . The overhead traveling vehicle  100  acquires, from a host controller or the like not shown in the drawings, position information of the cell C where the charger  50  is located. As shown in  FIG. 10(A) , the overhead traveling vehicle  100  is traveling on the first tracks R 1  in the −X direction toward the cell C where the terminal unit  52  is located. 
     As shown in  FIG. 10(B) , when the overhead traveling vehicle  100  reaches the cell C where the terminal unit  52  is arranged, the charging electrodes  17  of the overhead traveling vehicle  100  overlap with the terminals  52   b  of the terminal unit  52  as viewed in a plan view. The charging electrodes  17  and the terminal unit  52  are preliminarily positioned to oppose to each other when the overhead traveling vehicle  100  reaches the cell C. An example is described as an example in  FIG. 10  where the overhead traveling vehicle  100  is traveling on the first tracks R 1  in the −X direction. However, similarly, also when the overhead traveling vehicle  100  travels on the first tracks R 1  in the +X direction, the charging electrodes  17  and the terminal unit  52  oppose to each other as shown in  FIG. 10(B) . 
       FIG. 11  shows an example of when the overhead traveling vehicle  100  travels along the second tracks R 2 ,  FIG. 11(A)  being a diagram showing the overhead traveling vehicle  100  in a state of traveling toward the terminal unit  52 , and  FIG. 11(B)  being a diagram showing the overhead traveling vehicle  100  in a state of having reached below the terminal unit  52 . As shown in  FIG. 11(A) , the overhead traveling vehicle  100  is traveling on the second tracks R 2  in the +Y direction toward the cell C where the terminal unit  52  is located. 
     As shown in  FIG. 11(B) , when the overhead traveling vehicle  100  reaches the cell C where the terminal unit  52  is arranged, the charging electrodes  17  of the overhead traveling vehicle  100  overlap with the terminals  52   b  of the terminal unit  52  as viewed in a plan view. An example is described as an example in  FIG. 11  where the overhead traveling vehicle  100  is traveling on the second track R 2  in the +Y direction. However, similarly, also when the overhead traveling vehicle  100  travels on the second tracks R 2  in the −Y direction, the charging electrodes  17  and the terminal unit  52  oppose to each other as shown in  FIG. 11(B) . 
     As shown in  FIGS. 10 and 11 , the charging electrodes  17  and the terminal unit  52  can be brought into the state of opposing to each other in the cell C regardless of whether the overhead traveling vehicle  100  is traveling on the first tracks R 1  or is traveling on the second tracks R 2 . The overhead traveling vehicle  100  only causes the traveling wheels  21  to pivot and does not cause the main body  10  to rotate when shifting from the first track R 1  to the second track R 2  or from the second track R 2  to the first track R 1 . Therefore, if the positioning between the charging electrodes  17  and the terminal unit  52  is determined preliminarily, the charging electrodes  17  and the terminal unit  52  are brought to the state of opposing to each other when the overhead traveling vehicle  100  reaches the cell C regardless of whether the overhead traveling vehicle  100  travels on the first tracks R 1  or travels on the second tracks R 2 . 
     Information indicating that the overhead traveling vehicle  100  has reached the cell C can be acquired by position information transmitted from the overhead traveling vehicle  100  to the host controller. The control unit  53  of the charger  50  receives from the host controller information indicating that the overhead traveling vehicle  100  has reached the cell C, and causes the terminal unit  52  to operate on the basis of this information. The control unit  53  is not limited to acquiring from the host controller information indicating that the overhead traveling vehicle  100  has reached the cell C, and may acquire the information by receiving a signal by wireless communication or the like from the overhead traveling vehicle  100  which has reached the cell C. A sensor or the like may be arranged in the cell C, and information indicating that the overhead traveling vehicle  100  has reached the cell C may be acquired from the result of detection performed by the sensor. 
       FIG. 12  shows an example of an operation performed by the terminal unit  52 ,  FIG. 12(A)  being a diagram showing a state where the terminals  52   b  of the terminal unit  52  are away from the charging electrodes  17 , and  FIG. 12(B)  being a diagram showing a state where the terminals  52   b  of the terminal unit  52  are in contact with the charging electrodes  17 . At the timing when the overhead traveling vehicle  100  reaches the cell C where the terminal unit  52  is arranged, the holder  52   c  of the terminal unit  52  is located at the waiting position P 2  and the terminals  52   b  are away from and above the charging electrodes  17  as shown in  FIG. 12(A) . 
     From this state, the elevator  52   d  is driven to lower the holder  52   c  from the waiting position P 2  to the connection position P 1 . As shown in  FIG. 12(B) , this operation brings the two terminals  52   b  into contact respectively with the two charging electrodes  17 , and the terminals  52   b  and the charging electrodes  17  are electrically connected. As a result, electric power from the power supply unit  51  is supplied to the battery  16  via the terminals  52   b  and the charging electrodes  17 . When charging of the battery  16  is completed, the control unit  53  receives, for example, a charging completion signal from the overhead traveling vehicle  100  via the host controller or receives the signal directly and not via the host controller, and completes the charging operation on the basis of this information. After having stopped supplying electric power, the control unit  53  drives the elevator  52   d  to raise the holder  52   c  from the connection position P 1  to the waiting position P 2 . This operation brings the overhead traveling vehicle  100  into the state of being able to travel. 
     As described above, in the overhead traveling vehicle system SYS in this example, the charger  50  is arranged in a space, at least a part of which overlaps with a movement space K 1  for the traveling wheels  21  as viewed in a side view, and which does not overlap with the movement space K 1  for the traveling wheels  21  as viewed in a plan view. Therefore, while preventing the traveling wheels  21  from interfering with the charger  50 , it is possible to suppress the space for arranging the charger  50  above the grid-patterned track R. As a result, the grid-patterned track R can be arranged in the vicinity of the ceiling, and it is therefore possible to suppress a reduction in the efficiency of space utilization in the building. Since the charger  50  is arranged in the space which does not overlap with the movement space K 1  of the traveling wheels  21  as viewed in a plan view, the overhead traveling vehicle  100  traveling on the grid-patterned track R along the traveling surfaces R 1   a , R 2   a , and R 3   a  does not cause interference with the charger  50 , and the charging electrodes  17  can be positioned below the charger  50  from any direction. 
     An example of our systems has been described above. However, our systems are not limited to the above description, and various modifications may be made without departing from the scope of this disclosure. For example, the above example has been described, taking a configuration as an example in which the charging electrodes  17  are fixed to the upper surface  10   a  of the main body  10 , however, our systems are not limited to this configuration. For example, a configuration may be employed in which the charging electrodes  17  are raised or lowered by an elevator. In this configuration, the charging electrodes  17  may be arranged at a portion that overlaps with the pivoting space K 2  of the steerer  34  as viewed in a plan view. Also, in this configuration, the charging electrodes  17  and the terminals  52   b  may be brought into contact with each other by fixing the holder  52   c  of the terminal unit  52  and raising the charging electrodes  17 . 
     The above example has been described, taking a configuration of the grid-patterned track R as an example of the track in which a plurality of the first tracks R 1  and a plurality of the second tracks R 2  orthogonally intersect with each other, and a plurality of cells C are adjacent to each other as viewed in a plan view. However, our systems are not limited to this configuration. The track may be in the form of extending in one direction and having no intersections. 
     The above example has been described, taking a configuration as an example in which the charger  50  is arranged in a cell C, which is an intersection where the first tracks R 1  and the second tracks R 2  intersect with each other. However, our systems are not limited to this configuration. The charger  50  may be arranged at a location other than an intersection of the first tracks R 1  and the second tracks R 2 . 
     The above example has been described, taking an example where charging is performed by bringing the terminals  52   b  of the terminal unit  52  into contact with the charging electrodes  17  of the overhead traveling vehicle  100 . However, our systems are not limited to this configuration. For example, there may be applied a form in which electric power is supplied in a non-contact state where the terminals  52   b  and the charging electrodes  17  are away from each other (so-called non-contact power supply). Furthermore, the contents of Japanese Patent Application No. 2018-150670 and all documents cited in the detailed description are incorporated herein by reference.