Patent Publication Number: US-10328955-B2

Title: Plug door opening-closing device and plug door device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is a Continuation Application of U.S. Ser. No. 14/853,636, filed Sep. 14, 2015, which claims the benefit of priority from prior Japanese Patent Application No. 2014-191902, filed on Sep. 19, 2014. The subject matter of each is incorporated herein by reference in entirety. 
    
    
     FIELD 
     The present invention relates to a plug door opening-closing apparatus that moves a door panel in a vehicle front-rear direction and a vehicle width direction and a plug door device including the plug door opening-closing apparatus. 
     BACKGROUND 
     Japanese Laid-Open Patent Publication No. 2012-188858 describes a conventional sliding plug door device for a railway vehicle. The plug door device includes a plug door opening-closing apparatus that performs an operation for moving a door panel in the widthwise direction of a railway vehicle when sliding the door panel in the front-rear direction of the railway vehicle, that is, the so-called plugging operation. The plug door device further includes a fixed base and a movable base. The fixed base includes a front rail and a rear rail. The movable base includes a front roller and a rear roller respectively coupled to the front rail and the rear rail. The plug door opening-closing apparatus is mounted on the movable base. The front rail and the rear rail are fixed to a side wall of the vehicle body so that the plug door opening-closing apparatus is held in between in the front-rear direction. Each rail extends in the vehicle width direction. The movable base is movably supported by the two rails on the fixed base. When force that presses the movable base in the vehicle width direction is applied to the movable base, the front and rear rollers roll on the front and rear rails. This moves the movable base and the door panel relative to the fixed base in the vehicle width direction. 
     SUMMARY 
     In many cases, a plug door device including front and rear rollers and front and rear rails has predetermined gaps between the rollers and the corresponding rails. When the plug door device of the &#39;858 publication performs the plugging operation, such gaps may cause the movable base to be inclined relative to the vehicle front-rear direction. This causes the jamming of the front and rear rollers and the front and rear rails. In this specification, the jamming refers to a state in which a movable portion of a mechanical structure such as a sliding portion, a link mechanism, and a nut and a bolt is at least temporarily stuck and the movable portion is hindered from smoothly moving. 
     It is an object of the present invention to provide a plug door opening-closing apparatus and a plug door device that allow a door to stably move in the vehicle width direction. 
     One aspect of the present invention is a plug door opening-closing apparatus adapted for use with a vehicle having a vehicle front-rear direction and a vehicle width direction. The plug door opening-closing apparatus includes a door hanger, a movable guide, a guide support member, and an interlock mechanism. The door hanger is capable of coupling a door panel of the vehicle. The movable guide is configured to guide movement of the door hanger in the vehicle front-rear direction and move in the vehicle width direction. The guide support member guides movement of the movable guide in the vehicle width direction. The interlock mechanism is mechanically connected to the movable guide. The interlock mechanism conforms a movement amount of a first portion of the movable guide to a movement amount of a second portion of the movable guide. 
     In the above structure, the interlock mechanism conforms the movement amount of the first portion to the movement amount of the second portion. This prevents the movable guide, which is supported by the guide support member, from jamming in the vehicle front-rear direction when the movable guide moves in the vehicle width direction. Thus, the movable guide smoothly moves in the width direction, and movement of the door panel is stabilized in the width direction. The first portion and the second portion refer to portions of the movable guide that are located at different positions in the front-rear direction. The term “conform” includes complete conformance and also a slight difference to an extent that does not hinder movement in the width direction X. 
     In some implementations, the interlock mechanism includes a rotatable interlock shaft extending in the vehicle front-rear direction, and a plurality of link mechanisms linking the interlock shaft to the first portion and the second portion of the movable guide. 
     In the above structure, the movement amount of the first portion and the movement amount of the second portion may conform without using electrical components. Thus, the interlock mechanism functions even when no electric power is supplied. 
     In some implementations, each link mechanism includes a first link, which is coupled to the interlock shaft and rotated integrally with the interlock shaft, and a second link, which is coupled to the movable guide. In each link mechanism, the first link and the second link form a revolute pair. 
     For example, when the interlock mechanism has a structure in which force is transmitted with a rack and pinion mechanism, pitches of racks would need to be aligned. This requires high coupling precision and is burdensome. In this regard, the plug door opening-closing apparatus includes the interlock mechanism that transmits force using a plurality of links. This simplifies the coupling compared to when a rack and pinion mechanism is used. 
     In some implementations, the first portion and the second portion correspond to two opposite ends of the movable guide in the vehicle front-rear direction. 
     In the above structure, the door hanger moves between the front end and the rear end of the movable guide, to which the links are coupled. This allows for an increase in the length in which the door hanger moves on the movable guide compared to when the links are coupled to intermediate portions of the movable guide in the front-rear direction. More specifically, the open width of the door panel may be increased without increasing the size of the plug door opening-closing apparatus in the front-rear direction. 
     In some implementations, the second link is rotatable relative to the movable guide. 
     In the above structure, when coupling the first link and the second link, the second link may be rotated relative to the movable guide. This improves the task for coupling each link compared to when the second link is rotated together with the movable guide when coupled to the first link. 
     In some implementations, the movable guide is located at a first position in the vehicle width direction, and the interlock shaft is location at a second position in the vehicle width direction. The second position is located toward an inner side in the vehicle width direction from the first position. 
     In the above structure, the joint portion of the first link and the second link is located toward the vehicle inner side from the movable guide. This facilitates the task for coupling each link from the vehicle inner side. 
     In some implementations, the plug door opening-closing apparatus further includes a phase setting unit that sets a phase of the first link when coupled to the interlock shaft about an axis of the interlock shaft. 
     In the above structure, the coupling phases of the first links of the link mechanisms may conform to each other due to the phase setting unit. 
     In some implementations, the phase setting unit includes a hole, which is provided for each of the first link and the interlock shaft, and a screw inserted into the holes. The screw fastens the first link and the interlock shaft. 
     In the above structure, the screw sets the phase of the first link relative to the interlock shaft and positions the first link relative to the interlock shaft in the front-rear direction. Thus, the operation for engaging the screw simultaneously performs the setting of the phase, the positioning in the vehicle front-rear direction, and the fixing. This reduces the coupling task. 
     In some implementations, the first link is a crank-shaped mechanical component including a first arm coupled to the interlock shaft and rotated integrally with the interlock shaft, a second arm coupled to the second link, and a connection portion connecting the first arm and the second arm. The first arm is located toward a longitudinally outer side of the interlock shaft from the second arm. The second link and the first arm are located at the same side of the second arm in the vehicle front-rear direction. 
     The above structure allows for an increase in the length in which the door hanger moves on the movable guide compared to when the second link and the first arm are located at opposite sides of the second arm in the front-rear direction. More specifically, the open width of the door panel may be increased without enlarging the plug door opening-closing apparatus in the vehicle front-rear direction. 
     In some implementations, the plug door opening-closing apparatus further includes a rail plate that supports an inclined rail. The inclined rail includes an inclined portion, which is inclined relative to the vehicle width direction and the vehicle front-rear direction, and a straight rail, which extends in the vehicle front-rear direction. The rail plate includes a flange that extends in the vehicle front-rear direction. 
     In the above structure, the flange increases the rigidity of the rail plate and hinders deformation of the inclined rail. This stabilizes movement of the door panel. Additionally, the first arm is located at a longitudinally outer side of the interlock shaft. This prevents the flange from contacting the first arm even when the size of the flange is set to be increased in the front-rear direction. Thus, the rigidity of the rail plate is further increased. 
     In some implementations, the guide support member is a rail that extends in the vehicle width direction, and the movable guide is provided with a rotary body that rolls on the rail. 
     The above structure decreases friction between the movable guide and the rail. Thus, the movable guide moves in the width direction in a further smooth manner. 
     In some implementations, the movable guide is rotatable, and the rotary body is fixed to the movable guide. 
     The above structure eliminates the need for a rotary shaft and a bearing structure between the movable guide and the rotary body. Thus, the structure is simplified. 
     In some implementations, the plug door opening-closing apparatus further includes a stopper that cooperates with the rail to hold the rotary body in a radial direction of the rotary body. 
     When separation of the rotary body from the rail results in a plurality of links having different bent angles, the movable guide may be inclined. In this regard, the stopper hinders the separation of the rotary body from the rail. Thus, the bent angles of the links are maintained substantially the same. This stabilizes movement of the movable guide in the width direction. 
     In some implementations, the plug door opening-closing apparatus further includes a door driving mechanism and a link member. The door driving mechanism includes a threaded shaft extending in the vehicle front-rear direction and a nut engaged with the threaded shaft. The nut moves the door hanger in the vehicle front-rear direction. The link member links the threaded shaft and the movable guide. 
     In the above structure, the movable guide and the threaded shaft integrally move in the vehicle width direction. This provides the threaded shaft with the effect of the movable guide obtained due to the interlock mechanism. Consequently, the threaded shaft smoothly moves in the width direction, and the movement of the door panel in the width direction is further stabilized. 
     Additionally, when the movable guide rotates while moving in the width direction, the movable guide only needs to be arranged to be rotatable relative to the link member. This restricts interference of rotation of the movable guide by the link member. Thus, the movable guide may smoothly move in the width direction. 
     Another aspect of the present invention is a plug door device that includes a door panel for a vehicle and one of the plug door opening-closing apparatuses described above. 
     The aspects of the invention provide a plug door opening-closing apparatus and a plug door device that allow a door to stably move in the vehicle width direction. Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
         FIG. 1  is a front view showing one embodiment of a plug door device; 
         FIG. 2  is a bottom view showing the plug door device of  FIG. 1 ; 
         FIG. 3  is an exploded perspective view showing a portion of a door driving mechanism of  FIG. 2 ; 
         FIG. 4  is a rear view showing a frame of  FIG. 2  and its surrounding; 
         FIG. 5  is an exploded perspective view showing a portion of  FIG. 2 ; 
         FIG. 6  is a side view showing a plug door opening-closing apparatus; 
         FIG. 7  is a front view showing the frame of  FIG. 2  and its surrounding; 
         FIG. 8A  is a schematic bottom view showing the plug door opening-closing apparatus when a door panel is fully closed, and  FIG. 8B  is a perspective view showing a interlock mechanism when the door panel is fully closed; 
         FIG. 9A  is a schematic bottom view showing the plug door opening-closing apparatus when the door panel is moved to an outer side of a vehicle side wall, and 
         FIG. 9B  is a perspective view showing the interlock mechanism when the door panel is moved to the outer side of the vehicle side wall; 
         FIG. 10  is a schematic bottom view of the plug door opening-closing apparatus when the door panel is fully open; 
         FIG. 11  is a schematic bottom view showing a modified example of a plug door opening-closing apparatus; 
         FIG. 12  is a schematic bottom view showing another modified example of a plug door opening-closing apparatus; 
         FIG. 13  is a partial plan view showing a modified example of an interlock mechanism; 
         FIG. 14A  is a partial schematic side view showing another modified example of an interlock mechanism when the door panel is fully closed, and  FIG. 14B  is a partial schematic side view showing the modified example of the interlock mechanism when the door panel is moved to the outer side of the vehicle side wall; 
         FIG. 15  is a perspective view showing a portion of another modified example of an interlock mechanism; 
         FIG. 16  is a perspective view showing a modified example of an interlock shaft and a first link; 
         FIG. 17  is a front view showing a structure that supports a modified example of a movable guide when moving in the vehicle width direction; 
         FIG. 18  is a front view showing a structure that supports a modified example of a movable guide when moving in the vehicle width direction; and 
         FIG. 19  is a front view of a modified example of a plug door opening-closing apparatus showing a frame and its surrounding. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     With reference to  FIG. 1 , a plug door device  1  for a vehicle  200  will now be described. In the description, hereafter, axes X, Y, Z in the orthogonal coordinate system of  FIG. 1  refer to a vehicle width direction X, a vehicle front-rear direction Y, and a vehicle height direction Z, respectively. 
     The width direction X may refer to a plugging motion direction and an unplugging motion direction of a door panel  2 . In some examples, the width direction X refers to a direction that is intersected with or orthogonal to an outer or inner surface of the door panel  2 . The front-rear direction Y may refer to a sliding motion direction of the door panel  2 . The front-rear direction Y may refer to a sliding motion direction of the door panel  2 . In some examples, the front-rear direction Y refers to a horizontal direction that is substantially parallel to the outer or inner surface of the door panel  2 . 
     An entrance  211  of the vehicle  200  is formed in a vehicle side wall  210  of the vehicle  200 . A support pole  5 , which extends in the height direction Z, is coupled to the vehicle side wall  210  beside the entrance  211 . The plug door device  1  is coupled to the vehicle side wall  210  proximate to the entrance  211 . 
     The plug door device  1  includes the door panel  2 , which corresponds to the entrance  211 , and a plug door opening-closing apparatus  10 , which moves the door panel  2  in the width direction X and the front-rear direction Y. The plug door device  1  supports the door panel  2  so that the outer surface of the vehicle side wall  210  is flush with the outer surface of the door panel  2  when the door panel  2  is fully closed and entirely covers the entrance  211 . The plug door opening-closing apparatus  10  is arranged on an upper end of the door panel  2 . 
     The plug door device  1  includes three lock units  3 A to  3 C, which restrict movement of the door panel  2  in the width direction X and the front-rear direction Y, and a swing arm mechanism  4 , which guides or assists movement of the door panel  2  in the width direction X and the front-rear direction Y. 
     The lock unit  3 A is coupled to an upper portion of the support pole  5 . The lock unit  3 B is coupled to a middle portion of the support pole  5  in the height direction Z. The lock unit  3 C is coupled to a lower portion of the support pole  5 . The lock units  3 A and  3 C each include an electric motor (not shown) and a lock piece (not shown) used for holding the door panel  2 . When the door panel  2  is fully closed, the lock units  3 A and  3 C drive the electric motors to move the lock pieces toward the door panel  2 . Consequently, the door panel  2  is confined in the width direction X and the front-rear direction Y. The lock unit  3 B includes a solenoid (not shown) and a lock piece (not shown). When the door panel  2  is fully closed, the lock piece of the lock unit  3 B locks the door panel  2 . 
     When opening the door panel  2 , the solenoid and the electric motors are driven in a manner reversed from the above operation. 
     The swing arm mechanism  4  is located at a lower position than the lock unit  3 C. The swing arm mechanism  4  includes a swing arm, which supports a lower portion of the door panel  2 . When the swing arm is rotated to an outer side in the width direction X of the vehicle together with the door panel  2 , the swing arm mechanism  4  guides or assists the unplugging motion of the door panel  2 , that is, a motion in which the door panel  2  is moved to the outer side of the vehicle side wall  210 . 
     The structure of the plug door opening-closing apparatus  10  will now be described with reference to  FIGS. 2 to 7 .  FIGS. 2 to 7  each show the layout of components in the plug door opening-closing apparatus  10  when the door panel  2  (refer to  FIG. 1 ) is fully closed. 
     As shown in  FIG. 2 , the plug door opening-closing apparatus  10  includes a door driving mechanism  20 , which moves the door panel  2  in the width direction X and the front-rear direction Y, a rail block  30 , which guides the movement of the door panel  2  in the width direction X and the front-rear direction Y, and two frames  40 , which support the door driving mechanism  20 . 
     The rail block  30  is supported by a rail plate  50 , which is fixed to the vehicle side wall  210  (refer to  FIG. 1 ). The rail block  30  includes an inclined rail  31  having a groove that opens outward. The inclined rail  31  includes an inclined portion  32  and a straight portion  33 . The inclined portion  32  is inclined toward the vehicle outer side as extending toward a door opening side. The straight portion  33  extends in the front-rear direction Y. 
     The door driving mechanism  20  includes a threaded shaft  21  extending in the front-rear direction Y, a nut  22 , which is engaged with the threaded shaft  21  and moves on the threaded shaft  21 , and an electric motor  23 , which rotates the nut  22 . The threaded shaft  21 , the nut  22 , and the motor  23  are arranged at an inner side in the width direction X of the vehicle from the rail block  30 . The motor  23  may incorporate the nut  22 . 
     Additionally, the door driving mechanism  20  includes a movable guide  24  and a door hanger  25 . The movable guide  24  may be a single elongated member that extends in the front-rear direction Y and is movable relative to the frame  40  in the width direction X. The door hanger  25  is supported by the movable guide  24  and movable in the front-rear direction Y. The upper end of the door panel  2  is coupled to the door hanger  25 . The movable guide  24  may be an elongated member and is, for example, a pipe, preferably, a tubular pipe. The movable guide  24  is located toward the vehicle outer side from the threaded shaft  21  and parallel to the threaded shaft  21 . The door hanger  25  includes a roller (not shown), which rolls in the inclined rail  31  when the door hanger  25  moves. The door hanger  25  is coupled to the motor  23  by a coupling plate  26 . 
     The two frames  40  are located on front and rear ends of the plug door opening-closing apparatus  10  and fixed to the vehicle side wall  210 . 
     As shown in  FIG. 3 , each frame  40  includes a base  41  extending in the width direction X and an upper portion  42  extending upward from a portion of the base  41  which is located at the outer side in the width direction X of the vehicle. 
     The base  41  is L-shaped. A portion of the upper end of the base  41  located at the inner side in the width direction X of the vehicle includes a cover  43  projecting toward the center of the plug door opening-closing apparatus  10  in the front-rear direction Y. A rail  44 , which functions as a guide support member that guides movement of the movable guide  24  in the width direction X, is coupled to the base  41  and located at a lower position than the cover  43 . The rail  44  includes a plate-like attachment portion  45 , which extends in the width direction X and is coupled to the base  41  with bolts (not shown). A support portion  46  extends from the lower end of the attachment portion  45  in the width direction X. 
     A rotary body  27 , which is rotatable together with the movable guide  24  about the center axis of the movable guide  24 , is located on the support portion  46 . The rotary body  27  is fixed to an end coupler  28  (coupling member), which is coupled to an end of the movable guide  24  in the front-rear direction Y. The end coupler  28  is, for example, tubular and fitted into a hollow portion  24 A of the movable guide  24 . A flange  28 A is formed on an end of the end coupler  28  that is located toward the rotary body  27  in the front-rear direction Y. 
     Here, the rotary body  27  may be arranged to be rotatable relative to the movable guide  24  about the center axis of the movable guide  24 . 
     A link arm  29  (link member), which links the movable guide  24  and the threaded shaft  21 , is coupled to the end coupler  28  so that the link arm  29  comes into contact with the flange  28 A in the front-rear direction Y. The link arm  29  includes an annular guide link portion  29 A and a crank-like plate  29 B extending from the guide link portion  29 A. The guide link portion  29 A is coupled to the end coupler  28  and rotatable relative to the end coupler  28 . An end of the plate  29 B to which the threaded shaft  21  is coupled is located closer, in the front-rear direction Y, to the attachment portion  45  of the rail  44  than an end of the plate  29 B located toward the guide link portion  29 A. The threaded shaft  21  is coupled to an end of the plate  29 B located at the inner side in the width direction X so that the threaded shaft  21  cannot rotate relative to the plate  29 B. 
     The upper portion  42  of the frame  40  projects from the upper end of the base  41  toward the center of the plug door opening-closing apparatus  10  in the front-rear direction Y. A stopper  47 , which extends in the width direction X, is fixed to the lower end of the upper portion  42 . In the height direction Z, the lower surface of the stopper  47  is located in the same position as the lower surface of the cover  43 . The leveled lower surfaces prevent the breakage of the rotary body  27  that would occur when the rotary body  27  strikes a corner of the cover  43  or the stopper  47 . 
     A holding member  48  is fixed to an end surface of the upper portion  42  located at the vehicle inner side. The holding member  48  is arranged so that the holding member  48  is located at an upper position than the cover  43  and overlapped with the cover  43 . A through hole  48 A extends through the holding member  48  in the front-rear direction Y. The outer ring of a ball bearing  62  is coupled to the inner wall defining the through hole  48 A. 
     As shown in  FIG. 4 , the attachment portion  45  of the rail  44  is in contact with the base  41  in the front-rear direction Y. The lower end of the attachment portion is in contact with the base  41  in the height direction Z. Additionally, a lower portion of the rotary body  27 , which is coupled to the support portion  46  of the rail  44 , is opposed to the attachment portion  45  in the front-rear direction Y with a slight gap located in between. The rotary body  27  is held between the stopper  47  and the support portion  46  in the radial direction of the rotary body  27  (e.g., height direction Z). A slight gap is formed between the rotary body  27  and the stopper  47  in the height direction Z. 
     As shown in  FIG. 2 , the plug door opening-closing apparatus  10  includes an interlock mechanism  60 , which conforms movement amounts of two opposite ends of the movable guide  24  in the width direction X. The interlock mechanism  60  includes an interlock shaft  61  and two link mechanisms  70 , which link two opposite ends of the interlock shaft  61  in the front-rear direction Y and two opposite ends of the movable guide  24  in the front-rear direction Y. The two opposite ends of the movable guide  24  in the front-rear direction Y correspond to a first portion and a second portion. The interlock mechanism  60  conforms the movement amount of the first portion of the movable guide  24  to the movement amount of the second portion of the movable guide  24 . The movement amount of the first portion and the movement amount of the second portion refer to movement amounts in the same width direction X. The interlock mechanisms  60  is mechanically connected to the movable guide  24  so that the first portion and the second portion of the movable guide  24  move in parallel and in the same width direction X by the same movement amount, that is, perform parallel movement. 
     The two opposite ends of the interlock shaft  61  in the front-rear direction Y and the surrounds have the same structure. Also, the two link mechanisms  70  have the same structure. Thus, the structure of one end of the interlock shaft  61  in the front-rear direction Y and the structure of one of the link mechanisms  70  will be described below with reference to  FIGS. 5 to 7 . The structure of the other end of the interlock shaft  61  in the front-rear direction Y and the structure of the other link mechanism  70  will not be described. 
     As shown in  FIG. 6 , the interlock shaft  61  is located at an upper position than the movable guide  24  and toward the vehicle inner side from the movable guide  24 . Additionally, the interlock shaft  61  is located at an upper position than the motor  23  and the threaded shaft  21  and toward the vehicle outer side from the motor  23  and the threaded shaft  21 . Further, the interlock shaft  61  is located toward the vehicle inner side from a flange  51 . The flange  51  is formed by bending an end portion of the rail plate  50  downward that is located at an inner side in the width direction X. 
     As shown in  FIG. 5 , the inner ring of the ball bearing  62  is coupled to the end of the interlock shaft  61  in the front-rear direction Y. The interlock shaft  61 , which extends in the front-rear direction Y, is rotationally supported by the ball bearing  62  in the holding member  48 . 
     A through hole  61 A extends through the interlock shaft  61  in a direction orthogonal to the center axis of the interlock shaft  61 . 
     The link mechanism  70  includes a crank-shaped first link  71 , which is coupled to the interlock shaft  61  and rotatable integrally with the interlock shaft  61 , and a plate-like second link  72 , which is coupled to the movable guide  24  and rotatable relative to the movable guide  24 . The first link  71  and the second link  72  form a revolute pair. 
     The first link  71  includes a first arm  71 A coupled to the interlock shaft  61 , a second arm  71 B coupled to the second link  72 , and a connection portion  71 C connecting the first arm  71 A and the second arm  71 B. A pin  73  is fixed to the second arm  71 B. 
     The first arm  71 A is located toward a longitudinally outer side of the interlock shaft  61  from the second arm  71 B. The distal end of the first arm  71 A includes an insertion portion  71 D, which is a through hole extending through the first arm  71 A in the front-rear direction Y. The interlock shaft  61  is inserted into the insertion portion  71 D. A through hole  71 E extends through the first arm  71 A from an outer surface of the circumference of the insertion portion  71 D to the inner surface of the insertion portion  71 D. A threaded hole  71 F, which extends in the longitudinal direction of the first arm  71 A, is formed in a portion of the first arm  71 A opposed to the through hole  71 E. When a screw  74  is inserted into the through hole  61 A of the interlock shaft  61  and the through hole  71 E of the first arm  71 A and engaged with the threaded hole  71 F, the first arm  71 A is fixed to the interlock shaft  61 . In the present embodiment, the through hole  61 A of the interlock shaft  61 , the through hole  71 E of the first arm  71 A, and the screw  74  form a phase setting unit, which sets the phase of the first link  71  when coupled to the interlock shaft  61 . This structure reduces shear force applied to the screw  74 . Thus, the interlock shaft  61  and the first arm  71 A may be fixed in a further ensured manner. 
     Alternatively, the screw  74  may be engaged with a through hole that is formed instead of the through hole  61 A and the threaded hole  71 F. In this case, the coupling task may be reduced. 
     Further, a press-fitting pin may be used instead of a screw. 
     The second link  72  includes an annular guide link portion  72 A coupled to the movable guide  24 . An arm portion  72 B, which extends to the guide link portion  72 A, is coupled to the second arm  71 B. The guide link portion  72 A is coupled to the outer ring of a ball bearing  63 , which is coupled to an end of the movable guide  24  in the front-rear direction Y. This allows the second link  72  to rotate relative to the movable guide  24 . The arm portion  72 B is coupled to the pin  73  and rotatable relative to the pin  73 . 
     As shown in  FIG. 6 , the link mechanism  70  is located toward the vehicle outer side from the threaded shaft  21  and the electric motor  23 . The first link  71  is inclined toward the vehicle inner side as extending downward. The second link  72  is inclined upward as extending toward the vehicle outer side. The pin  73  is located at a lower position than the center axis of the threaded shaft  21  and the center axis of the movable guide  24  and toward the vehicle inner side from the center axis of the interlock shaft  61 . 
     As shown in  FIG. 7 , the first link  71  is coupled to the end of the interlock shaft  61  in the front-rear direction Y. The rail plate  50  includes a slot  52  where the first link  71  is opposed in the width direction X so that interference is avoided between the first link  71  and the rail plate  50  and between the screw  74  and the rail plate  50 . 
     The second link  72  and the first arm  71 A of the first link  71  are located at the same side of the second arm  71 B of the first link  71 . The link arm  29  is located toward the rotary body  27  from the second link  72  in the front-rear direction Y. The guide link portion  29 A is overlapped with the pin  73  in the width direction X. The plate  29 B is located toward the rotary body  27  from the second arm  71 B, the arm portion  72 B of the second link  72 , and the pin  73  in the front-rear direction Y and opposed to the second arm  71 B, the arm portion  72 B of the second link  72 , and the pin  73 . 
     The operation and effect of the plug door opening-closing apparatus  10  will now be described with reference to  FIGS. 8 to 10 . In the description below, a door closing-side link mechanism  70 A refers to a link mechanism  70  located at the door closing side in the front-rear direction Y, and a door opening-side link mechanism  70 B refers to a link mechanism  70  located at the door opening side in the front-rear direction Y. Additionally, to clearly show the operation of the plug door opening-closing apparatus  10 , the plug door opening-closing apparatus  10  in  FIGS. 8 to 10  may differ in dimensions and scale from that in  FIG. 2 . 
       FIG. 8A  shows the plug door opening-closing apparatus  10  when the door panel  2  is fully closed.  FIG. 8B  shows the interlock mechanism  60  when the door panel  2  is fully closed. As shown in  FIG. 8A , the door hanger  25  is located on a door closing-side end of the movable guide  24 . The roller (not shown) of the door hanger  25  is located on the inclined portion  32  of the inclined rail  31 . The motor  23  is located on a door closing-side portion of the threaded shaft  21 . 
     When moving the door panel  2  from a fully closed position, which is shown in  FIG. 8A , to a fully open position, which is shown in  FIG. 10 , the plug door device  1  drives the motor  23  to move the door panel  2  in the width direction X and then in the front-rear direction Y. When the door panel  2  is moved from the fully open position to the fully closed position, the plug door device  1  drives the motor  23  to move the door panel  2  in the front-rear direction Y and then in the width direction X. 
     When opening the door panel  2  from the fully closed state, the plug door device  1  drives the motor  23  to rotate the nut  22  forward. This moves the nut  22  and the motor  23  toward the door opening side relative to the threaded shaft  21 . Since the motor  23  is coupled to the door hanger  25  by the coupling plate  26 , the movement of the motor  23  provides the door hanger  25  with force that moves the door hanger  25  toward the door opening side. Due to the force applied to the door hanger  25 , the roller of the door hanger  25  moves toward the vehicle outer side along the inclined portion  32  of the inclined rail  31  while moving toward the door opening side. Consequently, the door panel  2  moves toward the vehicle outer side while moving toward the door opening side. Such movement of the door hanger  25  moves the movable guide  24  toward the vehicle outer side. At this time, the rotary bodies  27 , which are coupled to the two opposite ends of the movable guide  24 , roll on the corresponding rails  44 . 
     In accordance with the movement of the movable guide  24  toward the vehicle outer side, the link mechanisms  70 , which are located at the two opposite ends of the movable guide  24 , operate as follows. That is, as shown in  FIG. 8B , in accordance with the movement of the movable guide  24  toward the vehicle outer side, when the second link  72  of the door closing-side link mechanism  70 A moves toward the vehicle outer side, the pin  73  moves toward the vehicle outer side. This pulls a joint portion of the first link  71  and the second link  72  toward the vehicle outer door and rotates the first link  71  together with the interlock shaft  61  in a direction indicated by the white arrow. When the interlock shaft  61  rotates, the first link  71  of the door opening-side link mechanism  70 B rotates in the same direction as the first link  71  of the door closing-side link mechanism  70 A. This moves the pin  73  of the door opening-side link mechanism  70 B toward the vehicle outer side. Accordingly, the second link  72  of the door opening-side link mechanisms  70 B moves toward the vehicle outer side. Consequently, the second link  72  of the door opening-side link mechanism  70 B pushes the movable guide  24  toward the vehicle outer side, and a door opening-side end of the movable guide  24  moves toward the vehicle outer side. In this manner, the movement amount of the door closing-side end of the movable guide  24  conforms to the movement amount of the door opening-side end of the movable guide  24  due to the interlock shaft  61 , the door closing-side link mechanism  70 A, and the door opening-side link mechanism  70 B. This hinders the movable guide  24  from inclining relative to the front-rear direction Y and results in no jamming. The term “conform” includes complete conformance and also a slight difference to an extent that does not hinder movement of the movable guide  24  in the width direction X. This is because the movable guide  24  only needs to move in the width direction X without jamming. 
     In this example, the operation starting from the door closing-side link mechanism  70 A is illustrated. However, the operation is the same when starting from the door opening-side link mechanism  70 B. 
     As shown in  FIG. 8A , when the movable guide  24  moves toward the vehicle outer side, the threaded shaft  21 , which is linked to the movable guide  24  by the link arm  29 , moves together with the movable guide  24  toward the vehicle outer side. The motor  23  moves together with the threaded shaft  21  toward the vehicle outer side. 
     As shown in  FIG. 9A , when the electric motor  23  further moves toward the door opening side and the roller of the door hanger  25  passes the inclined portion  32  of the inclined rail  31 , the movement of the movable guide  24  and the door hanger  25  toward the vehicle outer side is restricted. This restricts outward movement of the door panel  2  in the width direction X. At this time, as shown in  FIG. 9B , a bent angle is increased in each of the door closing-side link mechanism  70 A and the door opening-side link mechanism  70 B. Here, the bent angle refers to an angle between a first link  71  and a corresponding second link  72 , more specifically, an angle formed between a straight line connecting the center axis of the interlock shaft  61  and the center axis of the pin  73  and a straight line connecting the center axis of the pin  73  and the center axis of the movable guide  24  as the link mechanisms  70  are viewed in the front-rear direction Y. 
     Then, when the motor  23  further moves toward the door-opening side in the front-rear direction Y, the roller of the door hanger  25  moves along the straight portion  33  of the inclined rail  31 . This moves the door panel  2  toward the door opening-side in the front-rear direction Y. 
     Then, as shown in  FIG. 10 , the motor  23  stops after moving to a door opening-side end of the threaded shaft  21 . In accordance with the movement of the motor  23 , the door hanger  25  moves to the door opening-side end of the movable guide  24 . At this time, the door panel  2  is in the fully open position. When the door panel  2  only moves in the front-rear direction Y, the door closing-side link mechanism  70 A and the door opening-side link mechanism  70 B remain in the same state as that shown in  FIG. 9B . 
     When closing the door panel  2  from the fully open position shown in  FIG. 10 , the plug door device  1  drives the motor  23  to reversely rotate the nut  22 . This moves the motor  23 , the door hanger  25 , and the door panel  2  toward the door closing side in the front-rear direction Y. When the roller of the door hanger  25  travels in the inclined portion  32  of the inclined rail  31 , the motor  23 , the door hanger  25 , and the door panel  2  move toward the door closing side in the front-rear direction Y and the vehicle inner side. Consequently, the door panel  2  is fully closed. 
     The plug door device  1  of the present embodiment has the advantages described below. 
     (1) The plug door opening-closing apparatus  10  includes the interlock mechanism  60  that conforms the movement amount of the two opposite ends of the movable guide  24 , which moves in the width direction X. This prevents the movable guide  24 , which is supported by the rails  44 , from jamming when moving in the width direction X. Thus, the movable guide  24  smoothly moves in the width direction X, and the movement of the door panel  2  is stabilized in the width direction X. 
     (2) The interlock mechanism  60  includes the interlock shaft  61  extending in the front-rear direction Y and the link mechanisms  70  coupling the interlock shaft  61  and the movable guide  24  at the two opposite ends. Even when no electric power is supplied, the movement amounts of the two opposite ends of the movable guide  24  are conformed to each other by the link mechanisms  70 . More specifically, even when the vehicle  200  is not supplied with electric power, the interlock mechanism  60  functions and the door panel  2  may be smoothly opened and closed. 
     (3) For example, when an interlock mechanism is configured to transmit force using a rack and pinion mechanism, pitches of racks would need to be aligned with one another. This requires high coupling precision and is burdensome. However, the plug door opening-closing apparatus  10  of the embodiment includes the interlock mechanism  60  including the two link mechanisms  70 . The link mechanisms  70  transmit force between the first portion and the second portion of the movable guide  24 . Each link mechanism  70  couples the interlock shaft  61  and the movable guide  24  by the first link  71  and the second link  72 , which is rotationally coupled to the first link  71 . This allows for easy coupling compared to when a rack and pinion mechanism is used. 
     (4) The two link mechanisms  70  are coupled to the two opposite ends of the movable guide  24  in the front-rear direction Y. Thus, the door hanger  25  moves between the two opposite ends of the movable guide  24  in the front-rear direction Y. This allows for an increase in the length in which the door hanger  25  moves on the movable guide  24  compared to when the two link mechanisms  70  are coupled to intermediate portions of the movable guide  24  in the front-rear direction Y. More specifically, the open width of the door panel  2  may be increased without increasing the size of the plug door opening-closing apparatus  10  in the front-rear direction Y. 
     (5) Each second link  72  is rotationally coupled to the movable guide  24 . Thus, when coupling the second link  72  and the corresponding first link  71 , the second link  72  may be rotated relative to the movable guide  24 . This improves efficiency of the task for coupling each link mechanism  70  compared to when the second link  72  is rotated together with the movable guide when coupling to the first link  71 . 
     (6) The interlock shaft  61  is located toward the vehicle inner side from the movable guide  24 . Thus, the joint portions of the first links  71  and the corresponding second links  72  are located toward vehicle inner side of the movable guide  24 . This facilitates the coupling of each link mechanism  70  when one couples the link mechanism  70  from the vehicle inner side. 
     (7) The interlock mechanism  60  includes the phase setting unit that sets at least the phase of each first link  71  when coupled to the interlock shaft  61 . The coupling phases of the first links  71  of the link mechanisms  70  may conform to each other due to the phase setting unit. 
     (8) The phase setting unit of the interlock mechanism  60  includes the through holes  61 A of the interlock shaft  61 , the through holes  71 E of the first links  71 , and the screws  74 , which are inserted through the through holes  61 A,  71 E to fasten the interlock shaft  61  and the first links  71 . Thus, each screw  74  sets the phase of the corresponding first link  71  relative to the interlock shaft  61  and positions the first link  71  relative to the interlock shaft  61  in the front-rear direction Y. Therefore, the operation for engaging the screw  74  simultaneously performs the setting of the phase, the positioning in the front-rear direction Y, and the fixing. This reduces the coupling task. 
     (9) In the front-rear direction Y, each second link  72  and the first arm  71 A of the corresponding first link  71  are located at the same side of the second arm  71 B. This allows for an increase in the length in which the door hanger  25  moves on the movable guide  24  compared to when the second link  72  and the second arm  71 B are located at opposite sides of the first arm  71 A. That is, the open width of the door panel  2  may be increased without increasing the size of the plug door opening-closing apparatus  10  in the front-rear direction Y of the vehicle  200 . 
     (10) The rail plate  50  includes the flange  51  extending in the front-rear direction Y. The flange  51  increases the rigidity of the rail plate  50 . This hinders deformation of the inclined rail  31  of the rail block  30 , which is supported by the rail plate  50 , and stabilizes movement of the door panel  2 . Additionally, the first arms  71 A of the first links  71  are located at the longitudinally outer sides of the interlock shaft  61 . This prevents the flange  51  from contacting the first arms  71 A, more particularly, screw heads  74 A of the screws  74 , even when the size of the flange  51  is set to be increased in the front-rear direction Y. Thus, the rigidity of the rail plate  50  is further increased. 
     (11) The rotary bodies  27  are coupled to the two opposite ends of the movable guide  24  and rotatable relative to the movable guide  24 . This decreases the friction between the movable guide  24  and the rails  44 . Thus, the movable guide  24  moves in the width direction X in a further smooth manner. 
     (12) When separation of the rotary bodies  27  from the corresponding rails  44  results in the two link mechanisms  70  having different bent angles, the movable guide  24  may be inclined relative to the front-rear direction Y and jamming may be occurred. Thus, it is preferred that the plug door opening-closing apparatus  10  includes the stoppers  47 , which cooperate with the corresponding rails  44  to hold the corresponding rotary bodies  27  in the radial direction of the rotary bodies  27 . The stoppers  47  hinder the separation of the rotary bodies  27  from the rails  44  and maintains the bent angles of the two link mechanisms  70  substantially the same. Thus, movement of the movable guide  24  is stabilized in the width direction X. 
     (13) The plug door opening-closing apparatus  10  includes the link arms  29 , which link the threaded shaft  21  and the movable guide  24 . The movable guide  24  is rotatable relative to the link arms  29 . Thus, the movable guide  24  and the threaded shaft  21  integrally move in the width direction X. This provides the threaded shaft  21  with the effect of the movable guide  24  obtained due to the interlock mechanism  60 . Consequently, the threaded shaft  21  smoothly moves in the width direction X, and the movement of the door panel  2  in the width direction X is further stabilized. Additionally, when the movable guide  24  rotates while moving in the width direction X, interference of the rotation of the movable guide  24  by the link arms  29  is restricted. Thus, the movable guide  24  may smoothly move in the width direction X. 
     (14) The lower end of the attachment portion  45  of each rail  44  is in contact with the base  41  of the corresponding frame  40  in the front-rear direction Y. Thus, the rail  44  may be easily positioned relative to the frame  40  in the front-rear direction Y. Additionally, the force applied from the rotary body  27  to the support portion  46  of the rail  44  is supported by the base  41 , which is in contact with the lower end of the attachment portion  45 . This limits deformation of the support portion  46  that would occur due to the force applied from the rotary body  27  to the support portion  46  of the rail  44 . 
     Additionally, the attachment portion  45  of the rail  44  is in contact with the base  41  of the frame  40  in the front-rear direction Y. Thus, the rail  44  may be easily positioned relative to the frame  40  in the front-rear direction Y. 
     (15) The attachment portion  45  of the rail  44  is opposed to the rotary body  27  in the front-rear direction Y having a slight gap located in between. This restricts inclination of the rotary body  27  relative to the height direction Z and movement of the rotary body  27  toward the end of the plug door opening-closing apparatus  10  in the front-rear direction Y. 
     (16) The cover  43  of each frame  40  covers an upper side of the corresponding link arm  29 . Thus, the cover  43  restricts upward movement of the link arm  29 . This hinders the two opposite ends of the threaded shaft  21  in the front-rear direction Y from moving upward relative to the movable guide  24 . 
     (17) In the crank-shaped plate  29 B of each link arm  29 , the vehicle outer end is located toward the end of the movable guide  24  in the front-rear direction Y from the vehicle inner end. Thus, the pin  73  of each link mechanism  70 , which is opposed to the vehicle outer end of the corresponding plate  29 B in the front-rear direction Y, tends to be located toward the end of the movable guide  24  in the front-rear direction Y. This allows for an increase in the length in which the door hanger  25  moves on the movable guide  24 . 
     (18) The interlock shaft  61  is located at an upper position than the movable guide  24  and toward the inner side from the movable guide  24 . This limits enlargement of the plug door opening-closing apparatus  10  in the height direction Z and allows for a compact structure compared to when the interlock shaft  61  is located at a lower position than the movable guide  24  and when the interlock shaft  61  is located at the same position as the movable guide  24  in the width direction X. Additionally, compared to when the interlock shaft  61  is located at the same position as the movable guide  24  in the height direction Z, the gap may be decreased between the movable guide  24  and the motor  23  in the width direction X. This limits enlargement of the plug door opening-closing apparatus  10  in the width direction X and allows for a compact structure. 
     It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms. 
     Modified Example 1 
     The interlock mechanism  60  may have any configuration.  FIG. 11  shows one example of an interlock mechanism  60  having a different configuration. The interlock mechanism  60  includes an actuator  90 , which applies force acting in the width direction X to the movable guide  24 , a first position sensor  91  and a second position sensor  92 , which detect the position of the movable guide  24 , and a controller (not shown), which controls the actuator  90 . 
     The actuator  90  includes a linear cylinder and may use an air pressure cylinder, an electric cylinder, or a hydraulic cylinder. The actuator  90  is coupled to the door opening-side end of the movable guide  24  so that force may be applied in two directions (vehicle inner side and vehicle outer side). The first position sensor  91  detects the position of the door closing-side end of the movable guide  24  in the width direction X. The second position sensor  92  detects the position of the door opening-side end of the movable guide  24  in the width direction X. One example of each of the position sensors  91 ,  92  is an optical sensor. 
     The controller performs feedback control on the actuator  90  in accordance with a detection result of each of the position sensors  91 ,  92 . In the feedback control, when displacement of the door closing-side end and the door opening-side end of the movable guide  24  is detected, position control is performed on the actuator  90  to reduce the displacement. When the actuator  90  applies force to the door opening-side end of the movable guide  24 , the door opening-side end is moved further due to the force applied from the actuator  90  in the width direction X. This reduces the displaced amount of the door opening-side end and the door closing-side end of the movable guide  24 . 
     Modified Example 2 
     In a further different configuration of the interlock mechanism  60 , the actuator  90  shown in  FIG. 11  is located at each of two opposite ends of the movable guide  24 . The controller performs feedback control on the two actuators  90  in accordance with a detection result of each of the position sensors  91 ,  92 . In this case, the actuators  90  do not have to be coupled as long as each actuator  90  applies force in one direction (vehicle outer side). 
     Modified Example 3 
       FIG. 12  shows a further different example of an interlock mechanism  60 . The actuator  90  of the interlock mechanism  60  is coupled so that force in the two directions (vehicle outer side and vehicle inner side) is applied to the rotary body  27  that is located at the door closing side of the movable guide  24 . The remaining configuration is substantially the same as that of the interlock mechanism  60  shown in  FIG. 11 . 
     When the movable guide  24  moves toward the vehicle outer side in accordance with movement of the door panel  2  from the fully open position to the fully closed position, the movement amount of the movable guide  24  may be larger at the door closing side than at the door opening side. In this regard, when the movable guide  24  moves toward the vehicle outer side, the actuator  90  of  FIG. 12  provides the door closing-side end of the movable guide  24  with force that pushes the movable guide  24  toward the vehicle outer side or pulls the movable guide  24  toward the vehicle inner side. This reduces the displaced amount of the door opening-side end and the door closing-side end of the movable guide  24 . 
     Modified Example 4 
     Instead of performing feedback control on the actuator  90 , the controller of the interlock mechanism  60  shown in  FIGS. 11 and 12  may control the actuator  90  so that the actuator  90  provides the movable guide  24  with force predetermined in advance through experiments or the like. 
     Modified Example 5 
     Instead of the interlock mechanism  60  of  FIG. 12 , a further different example of an interlock mechanism  60  includes elastic members. The elastic members couple the door closing-side end and the door opening-side end of the movable guide  24  to the vehicle outer ends of the corresponding frames  40 . One example of the elastic member is a coil spring. The coil springs are compressed when the movable guide  24  moves toward the vehicle outer side. In this structure, when the movable guide  24  moves toward the vehicle outer side, the coil springs apply force that pushes the movable guide  24  toward the vehicle outer side to the door closing-side end and the door opening-side end of the movable guide  24 . In this case, when the two ends are displaced, the force applied to one end is larger than that applied to the other end. The difference in force reduces the displaced amount of the positions of the door opening-side end and the door closing-side end of the movable guide  24 . 
     Modified Example 6 
     Instead of the interlock mechanism  60  of  FIG. 12 , a further different example of an interlock mechanism  60  provides each rotary body  27  with a brake mechanism. When the movable guide  24  moves toward the vehicle outer side, if the two opposite ends of the movable guide  24  are displaced, control is executed so that braking force applied to the rotary body  27  located at one end becomes larger than that applied to the rotary body  27  located at the other end. This reduces the displaced amount of the door opening-side end and the door closing-side end of the movable guide  24 . An electromagnetic brake may be used as the brake mechanism. 
     Modified Example 7 
       FIG. 13  shows an interlock mechanism  100 , which is a further different example of an interlock mechanism  60 . The interlock mechanism  100  includes rack gears  101  located along the corresponding rails  44 , first pinion gears  102  fixed to the movable guide  24 , a coupling shaft  103  located parallel to the movable guide  24 , second pinion gears  104  fixed to the coupling shaft  103 , and a link plate  105  that couples the movable guide  24  and the coupling shaft  103 . The movable guide  24  and the coupling shaft  103  are rotatable relative to the link plate  105 . Each of the pinion gears  102 ,  104  is engaged with the corresponding rack gear  101 . 
     The door driving mechanism  20  further includes pinion gears, which are coupled to the two opposite ends of the movable guide  24 , and rack gears extending in the width direction X. The pinion gears are engaged with the rack gears. 
     Modified Example 8 
     The interlock mechanism  60  includes gear trains  110  and rack gears  114 , such as that shown in  FIG. 14A , instead of the link mechanisms  70 . Each gear train  110  includes a first gear  111 , a second gear  112 , and a third gear engaged with the gears  111 ,  112 . The first gears  111  are respectively fixed to the two opposite ends of the movable guide  24 . The second gears  112  are respectively fixed to the two opposite ends of the interlock shaft  61 . Each first gear  111  is engaged with the corresponding rack gear  114 . 
     In the interlock mechanism  60 , when the movable guide  24  moves in the width direction X, the first gear  111  rotates in a direction indicated by the white arrow and, as shown in  FIG. 14B , the third gear  113  orbits around the first gear  111 . 
     Modified Example 9 
     Portions other than the two opposite ends of the movable guide  24  in the front-rear direction Y may serve as the first portion and the second portion of the movable guide  24 , and the interlock mechanism  60  may conform the movement amounts of the portions to each other. The interlock mechanism  60  only needs to conform the movement amounts of at least two portions of the movable guide  24  that are located at different positions in the front-rear direction Y. 
     Modified Example 10 
     The interlock mechanism  60  may include three or more link mechanisms  70 . When including three or more link mechanisms  70 , the interlock mechanism  60  conforms the amounts in which three or more portions of the movable guide  24  that are located at different positions in the front-rear direction Y move in the same width direction X. 
     Modified Example 11 
     The second link  72  of each link mechanism  70  may be arranged so that the second link  72  cannot rotate relative to the movable guide  24 . This eliminates the need for machining the inner circumference of the guide link portion  72 A and reduces the task for machining compared to when the second link  72  is arranged to be rotatable relative to the movable guide  24 . In this case, the rotary body  27  is arranged to be rotatable relative to the movable guide  24 . 
     Modified Example 12 
     A link mechanism  70  may be added to a middle portion of the movable guide  24  in the front-rear direction Y. This increases the resistance against the torsion of the interlock shaft  61 . 
     Modified Example 13 
     As shown in  FIG. 15 , each link mechanism  70  may include a plate-like first link  71  and a crank-like second link  72 . 
     Modified Example 14 
     Each first link  71  and each second link  72  may have any length. When the door panel  2  is fully closed, the position of the joint portion of each first link  71  and the corresponding second link  72  in the width direction X is geometrically determined based on the length and position of each link. In one example, the joint portion is located at a position toward the vehicle outer side from at least one of the interlock shaft  61  and the movable guide  24 . When the first link  71  is located downward in the vertical direction when the door panel  2  is fully closed, the size of the plug door opening-closing apparatus  10  may be reduced in the width direction X. 
     Modified Example 15 
     The interlock mechanism  60  may include a positioning member, which positions each second link  72  in the front-rear direction Y relative to the movable guide  24 . One example of the positioning member is a snap ring. 
     Modified Example 16 
     The structure of each phase setting unit, which sets the phase, that is, the circumferential position of the first link  71  relative to the interlock shaft  61 , may be modified as follows. 
     In a modified example shown in  FIG. 16 , the phase setting unit includes a recess  61 B formed in an end portion of the interlock shaft  61  and a projection  71 G formed on the first link  71 . In this structure, when the projection  71 G is fitted to the recess  61 B, the phase of the first link  71  is set relative to the interlock shaft  61  in the circumferential direction. Additionally, when the projection  71 G contacts the end of the recess  61 B, the phase of the first link  71  is set relative to the interlock shaft  61  in the axial direction. Alternatively, a projection may be formed on the interlock shaft  61  when a recess is formed in the first link  71 . 
     Modified Example 17 
     Any means may be used to fix each first link  71  to the interlock shaft  61  and includes, for example, weld, bond, press-fit, and a pin. When the first link  71  is fixed to the interlock shaft  61  by welding, bonding, or press-fitting, the phase setting units may be omitted from the interlock shaft  61 . 
     Modified Example 18 
     The number of the through holes  61 A of the interlock shaft  61 , the through holes  71 E of each first link  71 , and the screws  74  may each be changed to any number. 
     Modified Example 19 
     The interlock shaft  61  may be located at any position. For example, the interlock shaft  61  may be located toward the vehicle outer side from the movable guide  24 . 
     Modified Example 20 
     The rotary bodies  27  of the door driving mechanism  20  may be fixed to the movable guide  24  so that the rotary bodies  27  cannot rotate relative to the movable guide  24 . In this case, the bearing between the movable guide  24  and each rotary body  27  is omitted. This simplifies the structure. 
     Modified Example 21 
     The structure of the door driving mechanism  20 , which guides movement of the movable guide  24  in the width direction X, may be modified, for example, as follows. 
     The door driving mechanism  20  may include a pipe  120  fixed to each frame  40  and a slide shaft  121  fixed to an end of the movable guide  24  (refer to  FIG. 17 ) instead of the rails  44  and the rotary bodies  27 . The pipes  120  and the slide shafts  121  each extend in the width direction X. Each slide shaft  121  is inserted into the corresponding pipe  120  and movable relative to the pipe  120  in the width direction X. The pipes  120  each correspond to a guide support member. 
     Modified Example 22 
     The door driving mechanism  20  may include a guide rail  130  fixed to each frame  40  and a rotary body  131  coupled to an end of the movable guide (refer to  FIG. 18 ) instead of the rails  44  and the rotary bodies  27 . The guide rails  130  each extend in the width direction X. The rotary bodies  131  are located in the corresponding guide rails  130  and rotatable relative to the movable guide  24 . In this case, the guide rails  130  each correspond to a guide support member. 
     Modified Example 23 
     The door driving mechanism  20  may include recesses  24 B, which are formed in the circumferences of two opposite ends of the movable guide  24  and located on the support portions  46  of the corresponding rails  44  (refer to  FIG. 19 ). In this case, the rotary bodies  27  may be omitted. The two opposite ends of the movable guide  24  are respectively held between the rails  44  and the stoppers  47  in the radial direction. In this case, the two opposite ends of the movable guide  24  including the recesses  24 B each function as a rotary body. 
     Modified Example 24 
     Instead of the recesses  24 B of the movable guide  24  and the rails  44  shown in  FIG. 19 , the two opposite ends of the movable guide  24  may be located on support surfaces of the corresponding frames  40 . This allows for omission of the rotary bodies  27  and the rails  44 . In this case, the support surfaces of the frames  40  each correspond to a guide support member, and the two opposite ends of the movable guide  24  each correspond to a rotary body. 
     Modified Example 25 
     The cover  43  of each frame  40  may have any length. For example, when the cover  43  is formed in a range from an inner end to an outer end of the base  41 , the stopper  47  may be omitted. 
     Modified Example 26 
     The link arms  29  may have any shape and be, for example, plate-like. 
     Modified Example 27 
     The door driving mechanism  20 , which moves the door hanger  25  in the front-rear direction, may be of a type in which the threaded shaft  21  is rotated with the motor  23 , a belt drive transmission device, or of a rack and pinion type. 
     Modified Example 28 
     The door opening type of the plug door device  1  may be of a double door type. For example, a pair of swing arm mechanisms  4  may correspond to a pair of the door panels  2 . 
     The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. Also, in the above detailed description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.