Abstract:
The present invention provides a vehicle step device, capable of enhancing operability of a step having an elevating function to enhance ingress/egress ease into and from the vehicle. The step device includes an opening/closing mechanism that operates in synchronization with opening and closing operations of a slide door, and a step moving mechanism that transmits power of the opening and closing operations of the slide door through the opening/closing mechanism to a movable step, thereby moving the movable step. The step moving mechanism includes a slide lever for moving the movable rails forward and backward, X arms each having first and second arms and provided between each movable rail and the movable step, and a vertically moving lever that moves the first end of the first arm with respect to the movable rails to vertically move the movable step.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a step device for a vehicle. 
     BACKGROUND OF THE INVENTION 
     Generally, in a vehicle such as a minivan, the height of the floor of the vehicle from the ground is set relatively high. Therefore, an entrance of the vehicle is provided with a step having a lower height than the floor of the vehicle. Patent Document 1 describes a vehicle step device that includes a movable step having not only a slide function but also an elevating function for further enhancing ingress/egress ease into or from the vehicle. When the entrance is opened by a vehicle door, the movable step is moved to a position closer to the ground, thereby reducing a vertical difference between the movable step and the ground, i.e., thereby reducing the height of the first step of a passenger who steps on the movable step from the ground at the time of getting on the vehicle, and the height of the last step of a passenger who steps on the ground from the movable step at the time of getting off the vehicle. 
     However, although the vehicle step device described in Patent Document 1 includes the movable step for making it possible for aged people or people with lower limb disabilities to easily get on or off the vehicle, it is necessary to manually deploy the movable step. Therefore, for example, when there is no helper, a person who gets on or off the vehicle must operate the step in a state where the person bends his or her knees at the time of getting on the vehicle or the person extends his or her hand to the step located lower than a floor surface of the vehicle at the time of getting off the vehicle. That is, an action that is more difficult than ingress/egress motion is required. 
     Patent Document 1: Japanese Laid-Open Patent Publication No. 2003-72466 
     DISCLOSURE OF THE INVENTION 
     It is an objective of the present invention to provide a step device for a vehicle, capable of enhancing operability of a step having an elevating function for enhancing ingress/egress ease into and from the vehicle. 
     To achieve the foregoing objective and in accordance with one aspect of the present invention, a step device for a vehicle is provided, which device includes a step provided on a vehicle entrance that is opened and closed by a vehicle door, a first transmitting mechanism that is operated in synchronization with opening and closing operations of the vehicle door, and a second transmitting mechanism that transmits, to the step, power of the opening and closing operations of the vehicle door transmitted through the first transmitting mechanism, thereby moving the step. The second transmitting mechanism includes a movable member, a slide lever, an arm mechanism, and a vertically moving lever. The movable member can move forward and backward with respect to a vehicle body. The slide lever moves the movable member forward and backward. The arm mechanism has first and second arms that are provided between the movable member and the step and turnably connected to each other at their central portions in their longitudinal directions. The first and second arms each include a first end connected to the movable member and a second end connected to the step. The vertically moving lever moves the first end of the first arm with respect to the movable member, thereby vertically moving the step. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a vehicle step device according to a first embodiment of the present invention in a state where a movable step is retracted; 
         FIG. 2  is a plan view of the vehicle step device shown in  FIG. 1  in a state where the movable step is projected; 
         FIG. 3  is a plan view showing the vehicle step device shown in  FIG. 1  in a state where the movable step is lowered; 
         FIG. 4  is a cross-sectional view taken along line  4 - 4  in  FIG. 1 ; 
         FIG. 5  is a cross-sectional view taken along line  5 - 5  in  FIG. 1 ; 
         FIG. 6  is a cross-sectional view taken along line  6 - 6  in  FIG. 2 ; 
         FIG. 7  is a cross-sectional view taken along line  7 - 7  in  FIG. 3 ; 
         FIG. 8  is an enlarged plan view of a step moving mechanism in the vehicle step device shown in  FIG. 1 ; 
         FIG. 9  is an enlarged plan view of the step moving mechanism in the vehicle step device shown in  FIG. 2 ; 
         FIG. 10  is an enlarged plan view of the step moving mechanism in the vehicle step device shown in  FIG. 3 ; 
         FIG. 11  is an enlarged plan view of cams and levers in the vehicle step device shown in  FIG. 1 ; 
         FIG. 12  is an enlarged plan view of the cams and the levers in the vehicle step device shown in  FIG. 2 ; 
         FIG. 13  is an enlarged plan view of the cams and the levers in the vehicle step device shown in  FIG. 3 ; 
         FIG. 14  is a perspective view of the movable step of the vehicle step device shown in  FIG. 1 ; 
         FIG. 15  is a perspective view of the movable step of the vehicle step device shown in  FIG. 2 ; 
         FIG. 16  is a perspective view of the movable step of the vehicle step device shown in  FIG. 3 ; 
         FIG. 17  is a schematic diagram showing a vehicle to which the present invention is applied; 
         FIG. 18  is a plan view showing a vehicle step device according to a second embodiment of the present invention in a state where a movable step is retracted; 
         FIG. 19  is a plan view showing the vehicle step device shown in  FIG. 17  in a state where the movable step is projected and a state where an upward movement of the movable step is completed; 
         FIG. 20  is a plan view showing the vehicle step device shown in  FIG. 17  in a state where a downward movement of the movable step is started; 
         FIG. 21  is a plan view of the vehicle step device shown in  FIG. 17  in a state where the movable step is lowered; 
         FIG. 22  is a cross-sectional view taken along line  22 - 22  in  FIG. 18 ; 
         FIG. 23  is an enlarged view of  FIG. 18 ; 
         FIG. 24  is a cross-sectional view showing action of the vehicle step device shown in  FIG. 17  and its enlarged view; 
         FIG. 25  is a cross-sectional view showing action of the vehicle step device shown in  FIG. 17  and its enlarged view; 
         FIG. 26  is a cross-sectional view showing action of the vehicle step device shown in  FIG. 17  and its enlarged view; 
         FIG. 27  is a cross-sectional view showing action of the vehicle step device shown in  FIG. 17  and its enlarged view; 
         FIG. 28  is a cross-sectional view showing action of the vehicle step device shown in  FIG. 17  and its enlarged view; 
         FIG. 29  is an enlarged plan view of cams and levers in the vehicle step device shown in  FIG. 18 ; 
         FIG. 30  is an enlarged plan view of the cams and the levers in the vehicle step device shown in  FIG. 19 ; 
         FIG. 31  is an enlarged plan view of the cams and the levers in the vehicle step device shown in  FIG. 20 ; 
         FIG. 32  is an enlarged plan view of the cams and the levers in the vehicle step device shown in  FIG. 21 ; 
         FIG. 33  is a plan view showing a vehicle step device according to a third embodiment of the present invention in a state where a movable step is retracted; 
         FIG. 34  is a plan view showing the vehicle step device shown in  FIG. 33  in a first projecting state of the movable step; 
         FIG. 35  is a plan view showing the vehicle step device shown in  FIG. 33  in a second projecting state of the movable step; 
         FIG. 36  is a plan view showing the vehicle step device shown in  FIG. 33  in a state where the movable step is disconnected; 
         FIG. 37  is a plan view of the vehicle step device shown in  FIG. 33  in a state where the movable step is lowered; 
         FIG. 38  is an enlarged view of  FIG. 33 ; 
         FIG. 39  is a cross-sectional view showing action of the vehicle step device shown in  FIG. 33  and its enlarged view; 
         FIG. 40  is a cross-sectional view showing action of the vehicle step device shown in  FIG. 33  and its enlarged view; 
         FIG. 41  is a cross-sectional view showing action of the vehicle step device shown in  FIG. 33  and its enlarged view; 
         FIG. 42  is a cross-sectional view showing action of the vehicle step device shown in  FIG. 33  and its enlarged view; 
         FIG. 43  is a cross-sectional view showing action of the vehicle step device shown in  FIG. 33  and its enlarged view; 
         FIG. 44  is a cross-sectional view showing action of the vehicle step device shown in  FIG. 33  and its enlarged view; 
         FIG. 45  is an enlarged plan view of cams and levers in the vehicle step device shown in  FIG. 33 ; 
         FIG. 46  is an enlarged plan view of the cams and the levers in the vehicle step device shown in  FIG. 34 ; 
         FIG. 47  is an enlarged plan view of the cams and the levers in the vehicle step device shown in  FIG. 35 ; 
         FIG. 48  is an enlarged plan view of the cams and the levers in the vehicle step device shown in  FIG. 36 ; 
         FIG. 49  is an enlarged plan view of the cams and the levers in the vehicle step device shown in  FIG. 37 ; 
         FIG. 50  is a plan view showing cams and levers in a vehicle step device according to a fourth embodiment of the present invention in a state where a movable step is retracted; 
         FIG. 51  is a plan view of the cams and the levers shown in  FIG. 50  in a state where the movable step is projected; 
         FIG. 52  is a plan view of the cams and the levers shown in  FIG. 50  in a state where the movable step is lowered; 
         FIG. 53  is a cross-sectional view of a vehicle step device according to a fifth embodiment of the present invention, taken along line  5 - 5  in  FIG. 1 ; 
         FIG. 54  is a cross-sectional view of the vehicle step device according to the fifth embodiment of the present invention, taken along line  6 - 6  in  FIG. 2 ; 
         FIG. 55  is a cross-sectional view of the vehicle step device according to the fifth embodiment of the present invention, taken along line  7 - 7  in  FIG. 3 ; 
         FIG. 56  is a plan view of a step moving mechanism in a vehicle step device according to a sixth embodiment of the present invention; and 
         FIG. 57  is a cross-sectional view of a vehicle step device according to a modification of the present invention, taken along line  5 - 5  in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     A first embodiment according to the present invention will be described below in accordance with the drawings. 
       FIG. 17  is a schematic diagram showing a vehicle such as an automobile to which the invention is applied. As shown in  FIG. 17 , a door opening  1   a  as an entrance is formed in a side of a vehicle body  1 , which forms a main body of the vehicle. The door opening  1   a  is opened and closed by a slide door  2  as a vehicle door which moves in the front-rear direction of the vehicle. The vehicle floor  3  has a difference in level  3   a  at a location facing the door opening  1   a . The vehicle floor  3  is provided at its lower side with a movable step  4  as a step that can vertically move between an ascent position near a lower end of the door opening  1   a  and a descent position that is lower than the ascent position and is moved forward and backward (projects and retracts) in a widthwise direction of the vehicle from the difference in level  3   a.    
     Next, description will be given of structures of details concerning opening and closing operations of the slide door  2 , as well as a moving operation of the movable step  4  with reference to  FIGS. 1 to 16 .  FIGS. 1 and 3  are plan views of the slide door  2  in its fully opened state and its fully closed state, respectively.  FIG. 2  is a plan view of the movable step  4  in a state immediately after the projecting motion thereof is completed (slide projecting state). In these drawings, upper and lower sides correspond to an inner side (vehicle-inner side) and an outer side (vehicle-outer side) in the widthwise direction of the vehicle, and left and right sides correspond to front and rear sides of the vehicle.  FIGS. 4 and 5  are cross-sectional views taken along line  4 - 4  and line  5 - 5  in  FIG. 1 .  FIG. 6  is a cross-sectional view taken along line  6 - 6  in  FIG. 2  and  FIG. 7  is a cross-sectional view taken along line  7 - 7  in  FIG. 3 . 
     As shown in  FIGS. 4 to 7 , a box-like case  11  which opens toward outside of the vehicle is fixed in the vehicle body  1  below the vehicle floor  3  and a metal plate step panel  12  is provided on an inner surface of the bottom wall of the case  11 . A support panel  11   a  is fixed to the case  11 . The support panel  11   a  divides the interior of the case  11  at an intermediate portion in its height direction. An accommodation space S is formed below the support panel  11   a.    
     A pair of fixed rails  13  (see  FIGS. 1 to 3 ) extending so as to incline by a slight angle with respect to the widthwise direction of the vehicle are fixed to the step panel  12 , and movable rails  14  as movable members are slidably supported by the fixed rails  13 . Both movable rails  14 , for example, are connected to each other by a metal plate slide panel  15 . 
     An elongated hole  14   a  extending in the longitudinal direction is formed in an inner side surface of an intermediate portion of each movable rail  14  in its longitudinal direction. A pair of arms  42  and  43 , i.e., first and second arms  42  and  43  which are turnably connected to each other at their central portions form an X arm  41  as a link mechanism. A first end  42   a  of the first arm  42  is rotatably connected to each movable rail  14  such that the first end  42   a  can move along the elongated hole  14   a . A first end  43   a  of the second arm  43  is rotatably connected to an inner side surface of the distal end (vehicle-outer side end) of each movable rail  14  in its longitudinal direction. Central portions of the arms  42  and  43  in the longitudinal direction are rotatably connected to each other by a pin  44 . The first arm  42 , which is disposed on both movable rails  14 , is rotatably connected to a metal plate vertically moving panel  45  at the first end  42   a . That is, when the vertically moving panel  45  moves along the longitudinal direction of the elongated hole  14   a , the first end  42   a  of each arm  42  connected to the vertically moving panel  45  slides along the elongated hole  14   a  so as to vary the distance between the first ends  42   a  and  43   a  of the arms  42  and  43 . 
     An elongated hole  4   a  extending in the longitudinal direction of each movable rail  14  is formed in a side surface of a vehicle-outer side end of the movable step  4 . A second end  42   b  of the first arm  42  is rotatably connected to the movable step  4  such that the second end  42   b  can move along the elongated hole  4   a . Further, a second end  43   b  of the second arm  43  is rotatably connected to a side surface of a vehicle-inner side end of the movable step  4 . Therefore, when the first end  42   a  of each arm  42  moves toward the vehicle-outer side along the elongated hole  14   a  together with the vertically moving panel  45 , the X arm  41  “opens”, that is, the second ends  42   b  and  43   b  of the arms  42  and  43  move downward, and the movable step  4  connected to the second ends  42   b  and  43   b  moves downward (see  FIG. 7 ). On the other hand, when the first end  42   a  of each arm  42  moves toward the vehicle-inner side along the elongated hole  14   a  together with the vertically moving panel  45 , the X arm  41  “closes”, that is, the second ends  42   b  and  43   b  of the arms  42  and  43  move upward, and the movable step  4  connected to the second ends  42   b  and  43   b  moves upward (see  FIG. 6 ). 
     A guide rail  16  is disposed on the support panel  11   a  above the fixed rails  13  and the like. The guide rail  16  guides an opening/closing operation of the slide door  2 . More specifically, as shown in  FIG. 1 , the guide rail  16  has a curving portion  16   a  located at a middle portion of the guide rail  16  in its longitudinal direction and also includes an inclined portion  16   b  inclined inward in the widthwise direction of the vehicle at the front end of the curving portion  16   a  and a straight portion  16   c  extending rearward of the vehicle at the rear end of the curving portion  16   a.    
     On the other hand, the slide door  2  is provided at its lower portion with an arm  17  projecting inward of the vehicle, and a roller support member  18  is turnably connected to the distal end of the arm  17 . That is, the slide door  2  is connected to the roller support member  18  through the arm  17 . The roller support member  18  includes a pair of guide rollers  18   a , and a load roller  18   b  disposed between the guide rollers  18   a . Each guide roller  18   a  includes a rotation axis extending in a height direction of the vehicle (in a direction perpendicular to the sheet of  FIG. 1 ). The load roller  18   b  includes a rotation axis extending in a direction perpendicular to a plane including the rotation axes of both guide rollers  18   a . Each guide roller  18   a  is attached to the guide rail  16  such that the guide roller  18   a  can roll and the roller support member  18  is supported by the load roller  18   b  such that the roller support member  18  can roll on the support panel  11   a  (vehicle body  1 ). 
     Therefore, when the guide rollers  18   a  are guided by the guide rail  16 , the slide door  2  slides and moves in the front-rear direction of the vehicle so as to open and close the door opening  1   a . The load of the slide door  2  is supported by the load roller  18   b . Especially, when the guide rollers  18   a  are guided toward the front end (inclined portion  16   b ) of the guide rail  16 , the slide door  2  is pushed outward of the vehicle immediately after the slide door  2  opens from its fully closed state, or the slide door  2  is pulled inward of the vehicle immediately before the slide door  2  is fully closed. With this, the slide door  2  can be disposed such that rearward sliding motion thereof is permitted when the slide door  2  opens, and the slide door  2  is flush with a side surface of the vehicle body  1  when the slide door  2  is fully closed. 
     A mechanism for opening and closing the slide door  2  is mounted on the support panel  11   a  and the step panel  12  inside the guide rail  16  in the vehicle. More specifically, the support panel  11   a  includes a slide door drive unit  21  as an electric drive source, a plurality of idle gears  22 ,  23 ,  24 ,  25 ,  26  and  27  sequentially disposed in the clockwise direction from the slide door drive unit  21 , and a drive belt  28  that is wound around an output gear  21   a  of the slide door drive unit  21  and the idle gears  22  to  27  so as to mesh with the output gear  21   a  and the idle gears  22  to  27 . The idle gears  22  to  27  and the drive belt  28  constitute an opening/closing mechanism  29  as a first transmitting mechanism. 
     The slide door drive unit  21  is fixed to the support panel  11   a  and rotates an output gear  21   a  thereof. The idle gears  22  to  27  are rotatably supported by the support panel  11   a . The idle gears  23  and  22  are disposed near the front end and the rear end of the guide rail  16 , respectively. The idle gear  25  is disposed inward of the vehicle at an intermediate location between the idle gears  22  and  23 . An appropriate idle gear (not shown) with which the drive belt  28  meshes is disposed near the curving portion  16   a  between the idle gears  22  and  23 . 
     The distal end of the roller support member  18  is fixed to the drive belt  28  along the guide rail  16  between the idle gears  22  and  23 . The distal end of the roller support member  18  is disposed near the idle gear  23 , i.e., near the front end of the guide rail  16  in the fully closed state shown in  FIG. 1 . The distal end of the roller support member  18  is disposed near the idle gear  22 , i.e., near the rear end of the guide rail  16  in the fully opened state shown in  FIG. 3 . 
     Therefore, when the slide door drive unit  21  rotates the output gear  21   a  in the counterclockwise direction in  FIGS. 1 to 2 , the drive belt  28  moves in the direction of arrow X while rotating the idle gears  22  to  27 . At this time, the idle gear  25  rotates in the counterclockwise direction in the drawing. The slide door  2  connected to the drive belt  28  through the roller support member  18  and the like moves rearward of the vehicle along the guide rail  16  and opens the door opening  1   a.    
     On the other hand, when the slide door drive unit  21  rotates the output gear  21   a  in the clockwise direction in  FIGS. 2 and 3 , the drive belt  28  moves in the direction of arrow Y while rotating the idle gears  22  to  27 . At this time, the idle gear  25  rotates in the clockwise direction in the drawing. The slide door  2  connected to the drive belt  28  through the roller support member  18  moves forward of the vehicle along the guide rail  16  and closes the door opening  1   a.    
     As shown in  FIG. 4 , a gear  30  disposed below the idle gear  25  and coaxially with the idle gear  25  is rotatably supported by the step panel  12 . A torque limiter  31  which limits, to a given value, the torque that can be transmitted between the idle gear  25  and the gear  30  is provided between the idle gear  25  and the gear  30 . A disk-like plate cam  32  is rotatably supported by the step panel  12 . A gear portion  32   a  that meshes with the gear  30  is formed on an outer periphery of the plate cam  32 . 
     Therefore, the idle gear  25  rotates the gear  30  integrally with the idle gear  25  through the torque limiter  31  when the torque transmitted to the gear  30  is limited to the given value, thereby rotating the plate cam  32 . 
       FIGS. 8 to 10  are enlarged plan views of a step moving mechanism  50  shown in  FIGS. 1 to 3 , respectively.  FIGS. 11 to 13  are enlarged plan views of the cams and levers shown in  FIGS. 1 to 3 , respectively. As shown in these drawings, a groove cam  33  is formed on a lower surface of the plate cam  32 . The groove cam  33  includes a first recess  33   a  extending to have a radius that is varied with respect to a rotation axis of the plate cam  32  and a second recess  33   b  extending in an arcuate form to have a given radius with respect to the rotation axis of the plate cam  32 . The second recess  33   b  is connected to the first recess  33   a.    
     A first end  34   a  of an elongated slide lever  34  is rotatably connected to the step panel  12 . A second end  34   b  of the slide lever  34  is rotatably connected to the slide panel  15  so as to permit the slide panel  15  to move along the longitudinal direction of the fixed rails  13 . Therefore, when the slide lever  34  turns around the first end  34   a , the slide panel  15  connected to the second end  34   b  is pushed or pulled, and the slide panel  15  moves along the fixed rails  13  together with the movable rails  14 . 
     A bush  35  as a second follower member accommodated in the groove cam  33  is fixed to a longitudinal intermediate portion of the slide lever  34 . The bush  35  is set such that the bush  35  is located at a termination  33   c  of the first recess  33   a  when the slide door  2  is in the fully closed position (see  FIGS. 1 and 11 ) and the bush  35  is located at a termination  33   d  of the second recess  33   b  when the slide door  2  is in the fully opened position (see  FIGS. 3 and 13 ). That is, the bush  35  is set such that when movement of the slide door  2  from the fully closed position to the fully opened position is completed, the movement of the bush  35  from the termination  33   c  of the first recess  33   a  to the termination  33   d  of the second recess  33   b  is completed. 
     Further, the bush  35  is set such that when the slide door  2  reaches its predetermined open/close position (door opening degree position) at which a passenger of the vehicle can get on or off the vehicle, the bush  35  is located at a connection between the first and second recesses  33   a  and  33   b  (see  FIGS. 2 and 12 ). When the bush  35  is located in the first recess  33   a  (see  FIGS. 11 and 12 ), the plate cam  32  rotates and with this, the groove cam  33  (first recess  33   a ) pushes the bush  35 , thereby turning the slide lever  34  around the first end  34   a . As described above, as the slide lever  34  turns, the slide panel  15  is pushed or pulled, and the slide panel  15  is moved along the fixed rails  13  together with the movable rails  14 . At this time, the movable step  4  connected to the movable rails  14  through the X arms  41  is brought in or out (moved forward and backward). 
     Further, when the bush  35  is located in the second recess  33   b  (see  FIGS. 12 and 13 ), the groove cam  33  (second recess  33   b ) limits movement of the bush  35 , i.e., movement of the bush  35  in a radial direction with respect to the rotation axis of the plate cam  32 , thereby limiting the turning motion of the slide lever  34  around the first end  34   a  caused by rotation. 
     A groove cam  36  is formed in an upper surface of the plate cam  32 . The groove cam  36  includes a first recess  36   a  extending to have a radius that is varied with respect to the rotation axis of the plate cam  32 , a second recess  36   b  that extends continuously from the first recess  36   a  in an arcuate form such that the second recess  36   b  has a given radius with respect to the rotation axis of the plate cam  32 , a third recess  36   c  that extends continuously from the second recess  36   b  in a curved form such that the third recess  36   c  has a radius gradually increasing from the rotation axis of the plate cam  32 , and a fourth recess  36   d  that extends continuously from the third recess  36   c  in an arcuate form such that the fourth recess  36   d  has a given radius with respect to the rotation axis of the plate cam  32 . As viewed from above, positions of terminations  36   e  and  36   f  of the first and fourth recesses  36   a  and  36   d  match with the positions of terminations  33   c  and  33   d  of the first and second recesses  33   a  and  33   b  of the groove cam  33 , respectively. 
     The plate cam  32  is covered with a plate cam bracket  100  (see  FIG. 4 ) and a first end  37   a  of an elongated vertically moving lever  37  is rotatably connected to the plate cam bracket  100 . A second end  37   b  of the vertically moving lever  37  is rotatably connected to the vertically moving panel  45  so as to permit the vertically moving panel  45  to move along the longitudinal direction of the fixed rails  13  and the like. A first end  38   a  of an elongated lever  38  is rotatably connected to the plate cam bracket  100  and a second end  38   b  of the lever  38  is rotatably connected to the vertically moving lever  37  in the vicinity of the first end  37   a . Therefore, when the lever  38  turns around the first end  38   a , the vertically moving lever  37  connected to the second end  38   b  turns around the first end  37   a , the vertically moving panel  45  connected to the second end  37   b  is pushed or pulled, and is moved along the elongated holes  14   a  of the movable rails  14 . 
     A bush  39  as a first follower member accommodated in the groove cam  36  is fixed to a longitudinal intermediate portion of the lever  38 . The bush  39  is set such that when the slide door  2  is in the fully closed position, the bush  39  is located at the termination  36   e  of the first recess  36   a  (see  FIGS. 1 and 11 ), and when the slide door  2  is in the fully opened position, the bush  39  is located at the termination  36   f  of the fourth recess  36   d  (see  FIGS. 3 and 13 ). That is, the bush  39  is set such that when movement of the slide door  2  from the fully closed position to the fully opened position is completed, movement of the bush  39  from the termination  36   e  of the first recess  36   a  to the termination  36   f  of the fourth recess  36   d  is completed. 
     Further, the bush  39  is set such that when the slide door  2  reaches its predetermined open/close position (door opening degree position) at which a passenger of the vehicle can get on or off the vehicle, the bush  39  is located at a connection between the first and second recesses  36   a  and  36   b  (see  FIGS. 2 and 12 ). When the bush  39  is located in the first recess  36   a  (see  FIGS. 11 and 12 ), the plate cam  32  rotates and with this, the groove cam  36  (first recess  36   a ) pushes the bush  39 , thereby turning the lever  38  around the first end  38   a , and turning the vertically moving lever  37  around the first end  37   a  through the lever  38 . At this time, the vertically moving panel  45  is pushed or pulled, and is moved along the fixed rails  13 . In the present embodiment, the moving amount of the vertically moving panel  45  at this time is set such that the moving amount matches with the moving amount of the movable rails  14 , which moves at the same time along the fixed rails  13 . Therefore, the vertically moving panel  45  moves substantially integrally with the movable rails  14  at this time and does not move along the elongated holes  14   a . That is, the distance between the first ends  42   a  and  43   a  of each X arm  41  (arms  42  and  43 ) is constant, and the movable step  4  is not moved vertically. 
     When the bush  39  is located in the second recess  36   b  (see  FIG. 12 ), the groove cam  36  (second recess  36   b ) limits movement of the bush  39 , i.e., movement in the radial direction with respect to the rotation axis of the plate cam  32 . With this, the plate cam  32  limits the turning motion of the vertically moving lever  37  and the lever  38  around the first ends  37   a  and  38   a  caused by rotation. When the bush  39  is located in the third recess  36   c , the plate cam  32  rotates and with this, the groove cam  36  (third recess  36   c ) pushes the bush  39 , thereby turning the lever  38  around the first end  38   a , and turning the vertically moving lever  37  around the first end  37   a  through the lever  38 . The vertically moving panel  45  is pushed or pulled, and is moved along the elongated holes  14   a  of the movable rails  14 . The movable rails  14  are held stopped. As described above, the distance between the first ends  42   a  and  43   a  of the arms  42  and  43  is increased or reduced at this time, and the movable step  4  is moved vertically. 
     The vertically moving lever  37 , which turns around the first end  37   a  as the lever  38  is turned around the first end  38   a , is connected to the lever  38  at a location closer to the first end  37   a  than the bush  39  so as to increase the moving amount of the second end  37   b  connected to the vertically moving panel  45 . 
     When the bush  39  is located in the fourth recess  36   d , the groove cam  36  (fourth recess  36   d ) limits movement of the bush  39 , i.e., movement of the bush  39  in the radial direction with respect to the rotation axis of the plate cam  32 . With this, the plate cam  32  limits the turning motion of the vertically moving lever  37  and the lever  38  around the first ends  37   a  and  38   a  caused by rotation. The movable rails  14 , the slide lever  34 , the bush  35 , the vertically moving lever  37 , the lever  38 , the bush  39  and the X arms  41  constitute the step moving mechanism  50  as a second transmitting mechanism together with the gear  30  and the plate cam  32 . 
     Here, normal action of the present embodiment will be described. With this normal action, since torque transmitted between the idle gear  25  and the gear  30  is limited by the torque limiter  31 , this torque does not exceed a given value. 
     Assume that the slide door  2  is in the fully closed position and thus the movable step  4  is also pulled into the accommodation space S (accommodated state: see  FIGS. 1 ,  5 ,  8 ,  11  and  14 ). In this state, assume that the drive belt  28  is moved in the direction of arrow X shown in  FIGS. 1 to 2  to open the slide door  2 . At this time, the idle gear  25  rotates integrally with the gear  30  in the counterclockwise direction in the drawing. The plate cam  32 , which meshes with the gear  30 , rotates in the clockwise direction in the drawing together with the groove cams  33  and  36 . At this time, the bush  35  accommodated in the first recess  33   a  is pushed by the first recess  33   a , and the slide lever  34  to which the bush  35  is fixed turns around the first end  34   a  in the clockwise direction in the drawing. The slide panel  15  connected to the second end  34   b  of the slide lever  34  projects together with the movable rails  14  along the fixed rails  13 . Simultaneously, the bush  39  accommodated in the first recess  36   a  is pushed by the first recess  36   a , the lever  38  to which the bush  39  is fixed turns around the first end  38   a  in the counter clockwise direction in the drawing, and the vertically moving lever  37  connected to the second end  38   b  turns around the first end  37   a  in the clockwise direction in the drawing. The vertically moving panel  45  connected to the second end  37   b  of the vertically moving lever  37  projects along the fixed rails  13  substantially integrally with the movable rails  14 . The movable step  4  connected to the movable rails  14  through the X arms  41  projects without vertically moving. 
     When the slide door  2  reaches the predetermined open/close position at which a passenger of the vehicle can get on or off the vehicle, the bush  35  enters the second recess  33   b  from the first recess  33   a . Power transmission of the idle gear  25  and the gear  30  to the slide lever  34  through the plate cam  32  is cut, and the projecting operation of the movable step  4  is completed (slide projecting state: see  FIGS. 2 ,  6 ,  9 ,  12  and  15 ). At the same time, the bush  39  enters the second recess  36   b  from the first recess  36   a . Power transmission of the idle gear  25  and the gear  30  to the lever  38  and the vertically moving lever  37  through the plate cam  32  is temporarily cut. 
     When the slide door  2  is continuously opened in a state where the projecting operation of the movable step  4  is completed, the bush  39  enters the third recess  36   c  from the second recess  36   b . The bush  39  is pushed by the third recess  36   c  and the lever  38  further turns around the first end  38   a  in the counterclockwise direction in the drawing. At this time, the vertically moving lever  37  connected to the second end  38   b  further turns around the first end  37   a  in the clockwise direction in the drawing, the vertically moving panel  45  connected to the second end  37   b  is pushed, and the vertically moving panel  45  moves along the elongated holes  14   a  of the movable rails  14 . The movable rails  14  are held stopped. At this time, the distance between the first ends  42   a  and  43   a  of the arms  42  and  43  is reduced, the X arm  41  is opened and the movable step  4  moves downward. 
     When the bush  39  enters the fourth recess  36   d  from the third recess  36   c , power transmission of the idle gear  25  and the gear  30  to the lever  38  through the plate cam  32  is again cut, and the lowering operation of the movable step  4  is completed (lowered state: see  FIGS. 3 ,  7 ,  10 ,  13  and  16 ). The slide door  2  moves to the fully opened position in a state where the lowering operation of the movable step  4  is completed. 
     Assume that the drive belt  28  is moved in the direction of arrow Y shown in  FIG. 3  to close the slide door  2 , which is in the fully opened position. At this time, the idle gear  25  rotates integrally with the gear  30  in the clockwise direction in the drawing. The plate cam  32 , that meshes with the gear  30 , rotates in the counterclockwise direction in the drawing together with the groove cams  33  and  36 . At this time, the bushes  35  and  39  accommodated in the recesses  33   b  and  36   d  are not pushed by the recesses  33   b  and  36   d  of course. That is, at the initial stage of the closing operation of the slide door  2 , a force pushing the bushes  35  and  39  does not act and the movable step  4  is not operated. 
     When the bush  39  enters the third recess  36   c  from the fourth recess  36   d , the bush  39  is pushed by the third recess  36   c  and the lever  38  turns around the first end  38   a  in the clockwise direction in the drawing. At this time, the vertically moving lever  37  connected to the second end  38   b  turns around the first end  37   a  in the counterclockwise direction in the drawing, the vertically moving panel  45  connected to the second end  37   b  is pulled, and the vertically moving panel  45  moves along the elongated holes  14   a  of the movable rails  14 . The movable rails  14  are held stopped. At this time, the distance between the first ends  42   a  and  43   a  of the arms  42  and  43  is increased, the X arms  41  are closed, and the movable step  4  moves upward. 
     When the bush  39  enters the second recess  36   b  from the third recess  36   c , power transmission of the idle gear  25  and the gear  30  to the lever  38  through the plate cam  32  is temporarily cut, and the elevating operation of the movable step  4  is completed. 
     The slide door  2  is continuously closing in a state where the elevating operation of the movable step  4  is completed, and when the slide door  2  reaches the predetermined open/close position at which a passenger of the vehicle cannot get on or off the vehicle (see  FIGS. 2 ,  6 ,  9 ,  12  and  15 ), the bush  35  enters the first recess  33   a  from the second recess  33   b . Power transmission of the idle gear  25  and the gear  30  to the slide lever  34  through the plate cam  32  is connected, and the accommodating operation of the movable step  4  is started. The bush  35  accommodated in the first recess  33   a  is pushed by the first recess  33   a , the slide lever  34  to which the bush  35  is fixed turns around the first end  34   a  in the counterclockwise direction in the drawing. The slide panel  15  connected to the second end  34   b  of the slide lever  34  carries out the accommodating operation along the fixed rails  13  together with the movable rails  14 . At the same time, the bush  39  accommodated in the first recess  36   a  is pushed by the first recess  36   a , the lever  38  to which the bush  39  is fixed turns around the first end  38   a  in the clockwise direction in the drawing, and the vertically moving lever  37  connected to the second end  38   b  turns around the first end  37   a  in the counterclockwise direction in the drawing. The vertically moving panel  45  connected to the second end  37   b  carries out the accommodating operation along the fixed rails  13  substantially integrally with the movable rails  14 . The movable step  4  connected to the movable rails  14  through the X arms  41  carries out the accommodating operation without vertically moving. At the same time when the accommodating operation of the movable step  4  is completed, the slide door  2  moves to the fully closed position (see  FIGS. 1 ,  5 ,  8 ,  11  and  14 ). 
     As described above in detail, according to the present embodiment, the following advantages can be obtained. 
     (1) In the present embodiment, the movable rails  14  (slide panel  15 ), i.e., the movable step  4 , which is supported by the movable rails  14  through the X arms  41 , are moved forward and backward (projected and accommodated) by the slide lever  34  in synchronization with the opening/closing operation of the slide door  2 . The first ends  42   a  (vertically moving panel  45 ) of the first arms  42  of the X arms  41  are moved relative to the movable rails  14  by the vertically moving lever  37 , and the movable step  4  is vertically moved. Since the movable step  4  is operated in synchronization with the opening/closing operation of the slide door  2 , it becomes unnecessary for a person who gets on or off the vehicle to bend his or her knees to operate the movable step  4  at the time of getting on the vehicle. 
     (2) In the present embodiment, the opening/closing operation of the slide door  2  and the moving operation of the movable step  4  can be electrically carried out by the slide door drive unit  21 . 
     (3) In the present embodiment, the movable step  4  can be moved vertically in the projecting state of the movable step  4  with an extremely simple structure formed by engagement between the plate cam  32  (groove cam  36 ) and the bush  39 . Therefore, it is possible to reliably prevent such a case that the movable step  4  vertically moves during the forward or backward operation of the movable step  4  (movable rails  14  and slide panel  15 ) and interferes with the surrounding members. 
     (4) In the present embodiment, operation (turning motion) of the vertically moving lever  37  caused by vertical movement of the movable step  4  can be carried out indirectly based on the operation of the lever  38  to which the bush  39  is fixed. Thus, it is possible to enhance, for example, flexibility of settings of the moving amount (turning amount) of the vertically moving lever  37  with respect to the moving amount of the bush  39 . 
     (5) In the present embodiment, the plate cam  32  also functions as a member that moves the movable rails  14  (movable step  4 ) forward and backward and as a member that vertically moves the movable step  4 . With this, it is possible to prevent the number of parts from increasing. 
     Second Embodiment 
     A second embodiment according to the present invention will be described below based on  FIGS. 18 to 32 . To reduce the vertically moving lever in size (length), the structure of the second embodiment is different from that of the first embodiment in that the second embodiment has a lock mechanism that connects and disconnects the movable rails  14  (and slide panel  15 ) and the vertically moving panel with and from each other so that the vertically moving lever does not operate when the movable step  4  projects (slides). In the second embodiment, detailed explanation of the same portions as those of the first embodiment will be omitted. 
     As shown in  FIGS. 23 and 24 , in the present embodiment, a U-grooved lock lever  51  and a hook  52  are rotatably connected to an inner side surface of each movable rail  14 . The U-grooved lock lever  51  supported by a housing  54  receives a rotation force in the direction of arrow a by a spring  53 . Normally, a pawl  51   a  abuts against the housing  54  and stops. With this, a U-shaped opening  51   b  is directed to the direction of arrow n. A pawl  51   c  is in a position where the pawl  51   c  can abut against a lever  13   a  (see  FIG. 25 ) that is mounted on the bottom surfaces of the fixed rails  13 . Therefore, when the movable step  4  projects, the pawl  51   c  is pushed by the lever  13   a  and rotates in the direction of arrow b, and the U-shaped opening  51   b  is directed in the direction of arrow c. 
     The hook  52  is in either a position e (see  FIG. 24 ) or a position f (see  FIG. 26 ) by a spring  56 . When the hook  52  is in the position e, one side  52   a  of the hook  52  is in a position where the one side  52   a  can abut against a pawl  57   a  of a vertically moving panel  57  that connects both X arms  41  with each other. When the vertically moving panel  57  slides in the direction of arrow c, the pawl  57   a  pushes the one side  52   a  of the hook  52 , and the hook  52  rotates toward the position f (see  FIG. 26 ). On the other hand, when the hook  52  is in the position f, a pawl  52   b  of the hook  52  is in a position where the pawl  52   b  can abut against a lever  13   b  (see  FIG. 28 ) mounted on the bottom surface of each fixed rail  13 . The pawl  52   b  is pushed by the lever  13   b  at the time of the accommodating operation of the movable step  4 , and the hook  52  rotates toward the position e (see  FIG. 24 ). 
     The vertically moving panel  57  includes a pin  58  and a pin  59 . The pin  58  is fitted to the U-grooved lock lever  51  when the movable step  4  is in an elevated and accommodated state (see  FIG. 27 ). The pin  59  is fitted to an accommodating portion  52   c  when the hook  52  is in the position f. 
     A vertically moving lever  60  (see  FIGS. 29 to 32 ) that is shortened in the longitudinal direction as compared with the first embodiment is rotatably connected to the plate cam bracket  100  (see  FIG. 22 ). A bush  62  as a first follower member accommodated in a groove cam  61  formed on the plate cam  32  is fixed to a longitudinal intermediate portion of the vertically moving lever  60 . The vertically moving panel  57  is provided with a pin  63  at such a location that the pin  63  is separated away from the vertically moving lever  60  when the movable step  4  is in the accommodated state and the pin  63  enters a recess  60   a  of the vertically moving lever  60  when the movable step  4  is brought into the slide projecting state. The recess  60   a  of the vertically moving lever  60  includes a pawl  60   b  that pushes the pin  63  when the movable step  4  moves downward, and a pawl  60   c  that pushes the pin  63  when the movable step  4  moves upward. 
     Here, action of the present embodiment will be described. 
     First, assume that the movable step  4  is in the accommodated state (see  FIGS. 18 ,  24  and  29 ). When the slide lever  34  is rotated in the direction of arrow g from this state, the movable rails  14  are pushed and slid in the direction of arrow c. At this time, the movable step  4 , which is mounted on the movable rails  14  through the X arms  41 , also slides in the direction of arrow c. However, since the pin  58  provided on the vertically moving panel  57  is fitted to the U-grooved lock lever  51  provided on each movable rail  14 , the first end  42   a  of the first arm  42  of the X arm  41 , which is connected to the vertically moving panel  57 , cannot move relative to the movable rail  14 . Therefore, the movable step  4  is not lowered in the direction of arrow m by its own weight. 
     When the movable step  4  comes to the slide projecting position (see  FIGS. 19 ,  25  and  30 ), the pawl  51   c  is pushed by the lever  13   a  and rotates in the direction of arrow b, the U-shaped opening  51   b  is directed to the direction of arrow c, and the pin  58  is brought into a state where the pin  58  can move in the direction of arrow c (see  FIG. 25 ). At this time, the pin  63  provided on the vertically moving panel  57  enters the recess  60   a  of the vertically moving lever  60  (see  FIG. 30 ). At the same time, the vertically moving lever  60  starts rotating in the direction of arrow i by the groove cam  61 . The bush  35  enters the second recess  33   b  from the first recess  33   a  of the groove cam  33 . With this, the slide lever  34  is held at this position. 
     Next, when the movable step  4  comes to a lowering-starting position (see  FIGS. 20 ,  25  and  31 ), the pawl  60   b  pushes the pin  63  in the direction of arrow i. The vertically moving panel  57  moves in the direction of arrow c relative to the movable rails  14  such that the first end  42   a  of the first arm  42  of the X arms  41  moves in the elongated hole  14   a  in the direction of arrow c. At this time, the movable step  4  is lowered to the descent position (see  FIG. 26 ) in the direction of arrow m. When the pawl  57   a  of the vertically moving panel  57  pushes the one side  52   a  of the hook  52 , the hook  52  rotates from the position e (see  FIG. 25 ) to the position f (see  FIG. 26 ). 
     On the other hand, since a force is not applied to the pin  63  at the initial stage, the movable step  4  does not move when the vertically moving lever  60  rotates in the direction of arrow j from the lowered state (see  FIGS. 21 ,  26  and  32 ) of the movable step  4 . Thereafter, since the movable rails  14  are held by the slide lever  34 , the vertically moving panel  57  moves in the direction of arrow d relative to the movable rails  14  when the pawl  60   c  starts pushing the pin  63  in the direction of arrow j. The first end  42   a  of the first arm  42  of the X arm  41  moves in the elongated hole  14   a  in the direction of arrow d, and the movable step  4  starts moving upward in the direction of arrow n. 
     When the vertically moving panel  57  moves in the direction of arrow d relative to the movable rails  14  and comes to the elevated and accommodated position (see  FIG. 27 ), the pin  58  is accommodated in the U-grooved lock lever  51 . The pin  59  abuts against a slanting surface  52   d  of the hook  52 , and the pin  59  returns to a position where the pin  59  is fitted to the accommodating portion  52   c  of the hook  52  while pushing up the hook  52  toward the position e. At this time, the hook  52  is pushed up toward the position e but is not pushed up to such a level that the hook  52  returns to the position e. Therefore, when the pin  59  enters the accommodating portion  52   c , the hook  52  is returned to the position f by the spring  56 . 
     Next, when the slide lever  34  rotates in the direction of arrow h in the elevated and accommodated state of the movable step  4  (see  FIGS. 19 ,  27  and  30 ), the movable rails  14  are pushed and slid in the direction of arrow d. At this time, the movable step  4  mounted on the movable rails  14  through the X arms  41  also slides in the direction of arrow d. However, since the pin  59  provided on the vertically moving panel  57  is fitted to the hook  52  provided on each movable rail  14 , the first end  42   a  of the first arm  42  of each X arm  41  connected to the vertically moving panel  57  cannot move relative to the movable rail  14 . Thus, the movable step  4  does not move downward in the direction of arrow m by its own weight. The U-grooved lock lever  51  separates away from the lever  13   a , which has rotated the U-grooved lock lever  51  from the elevated and accommodated position in the direction of arrow b. Therefore, the U-grooved lock lever  51  is rotated by the spring  53  in the direction of arrow a, and the U-shaped opening  51   b  is directed in the direction of arrow n (see  FIG. 24 ). 
     When the movable step  4  returns to the accommodated state (see  FIGS. 24 and 28 ), the pawl  52   b  and the lever  13   b  abut against each other and the hook  52  rotates from the position f to the position e. 
     As described above in detail, according to the present embodiment, the following advantages can be obtained in addition to the advantages (1) to (3) and (5) of the first embodiment. 
     (1) In the present embodiment, the lock mechanism (lock lever  51 , the hook  52  and the like), which connects and disconnects the movable rails  14  and the vertically moving panel  57  with and from each other, is provided. With this, it becomes unnecessary to operate the vertically moving lever  60  when the movable rails  14  (movable step  4 ) slide and project, and the vertically moving lever  60  can further be reduced in length (size). 
     (2) Especially, since it is possible to control the operation of the lock mechanism using the mechanical linkage structure, the system configuration can be simplified as compared with an electrically controlled lock mechanism. 
     Third Embodiment 
     A third embodiment according to the present invention will be described below based on  FIGS. 33 to 49 . In the third embodiment, as a lock mechanism that connects and disconnects the movable rails  14  and the vertically moving panel with and from each other, a structure that is different from that of the second embodiment is employed. Therefore, in the third embodiment, detailed explanation of the same portions as those of the second embodiment will be omitted. 
     As shown in  FIGS. 38 and 39 , in the present embodiment, a hook  72  and a lever  73  are rotatably connected to a shaft  74  on a side surface of a vertically moving panel  71  that integrally connects both X arms  41  with each other. A spring  75  is assembled between a pawl  72   a  and a pawl  71   a  of the vertically moving panel  71 , and the spring  75  applies to the hook  72  a force for rotating the hook  72  in the direction of arrow k. A position of the hook  72  in its rotation direction is determined such that a pawl  72   b  of the hook  72  is fitted into an elongated hole  76  formed in a side surface of the vertically moving panel  71 . The hook  72  and the lever  73  are in contact with each other at a pawl  72   c  and one side  73   a.    
     An operation panel  78  is connected to the vertically moving panel  71  by fitting a pin  77  mounted on the operation panel  78  into an elongated hole  71   b  of the vertically moving panel  71 . The operation panel  78  is connected also to the lever  73  by a pin  79 . 
     A pin  81  is provided on a side surface of each movable rail  14  at a location where the pin  81  is fitted into a groove  72   d  of the hook  72  when the movable step  4  is at the same height as the movable rails  14 . A pin  82  (see  FIG. 33 ) that is connected to or disconnected from the vertically moving lever  60  is provided on the operation panel  78 . 
     Here, action of the present embodiment will be described. 
     First, assume that the movable step  4  is in its accommodated state (see  FIGS. 33 ,  38 ,  39  and  45 ). When the slide lever  34  is rotated in the direction of arrow g from this state, the movable rails  14  are pushed and slid in the direction of arrow c. The movable step  4  that is connected to the movable rails  14  through the X arm  41  also slides in the direction of arrow c. However, since the hook  72  provided on the vertically moving panel  71  is fitted to the pin  81  provided on the side surface of each movable rail  14 , the first end  42   a  of the first arm  42  of each X arm  41  connected to the vertically moving panel  71  cannot move relative to the movable rail  14 . Therefore, the movable step  4  does not move downward in the direction of arrow m by its own weight. 
     When the movable step  4  comes to a first slide projection position (see  FIGS. 34 ,  40  and  46 ), the pin  82  provided on the operation panel  78  enters the recess  60   a  in the vertically moving lever  60 . At the same time, the vertically moving lever  60  starts rotating in the direction of arrow i by the groove cam  61 . The bush  35  enters the second recess  33   b  from the first recess  33   a  of the groove cam  33  and with this, the slide lever  34  is held at this position. 
     Next, when the movable step  4  comes to a second slide projection position (see  FIGS. 35 ,  40  and  47 ), the pawl  60   b  of the vertically moving lever  60  starts pushing the pin  82  in the direction of arrow i. When the movable step  4  is lowered to a position where the movable rails  14  are disconnected (see  FIGS. 36 ,  41  and  48 ), the operation panel  78  moves in the direction of arrow c, and the lever  73  connected to the operation panel  78  through the pin  79  rotates in the direction of arrow  1 . When the one side  73   a  of the lever  73  pushes the pawl  72   c  of the hook  72  in the direction of arrow  1 , the hook  72  rotates in the direction of arrow  1 , the hook  72  is disengaged from the pin  81  provided on the side surface of each movable rail  14 , and the operation panel  78  and the movable rail  14  are disconnected from each other. 
     When the operation panel  78  further moves in the direction of arrow c, the pawl  72   b  of the hook  72  abuts against the one side  76   b  of the elongated hole  76 , rotation of the hook  72  is stopped, and a force received by the hook  72  is transmitted to the vertically moving panel  71  through the shaft  74 . At this time, since the movable rails  14  are held by the slide lever  34 , the vertically moving panel  71  moves in the direction of arrow c relative to the movable rails  14 . The first end  42   a  of the first arm  42  of the X arm  41  moves in the elongated hole  14   a  in the direction of arrow c, and the movable step  4  moves downward in the direction of arrow m (see  FIGS. 37 ,  42  and  49 ). 
     On the other hand, when the vertically moving lever  60  rotates in the direction of arrow i from the lowered state of the movable step  4  (see  FIGS. 37 ,  42  and  49 ), since a force is not applied to the pin  82  at the initial stage, the movable step  4  is not moved. Thereafter, when the pawl  60   c  of the vertically moving lever  60  starts pushing the pin  82  in the direction of arrow j, the operation panel  78  moves in the direction of arrow d, and the lever  73  connected by the pin  79  rotates in the direction of arrow k. The hook  72  is rotated in the direction of arrow k by the spring  75 , and the pawl  72   b  returns to a position where the pawl  72   b  abuts against the one side  76   a  of the elongated hole  76  and stops, i.e., a position where the pin  81  can be fitted into the groove  72   d  of the hook  72  (see  FIG. 43 ). 
     Thereafter, a force received by the hook  72  is transmitted to the vertically moving panel  71  through the shaft  74 . Since the movable rails  14  are held by the slide lever  34 , the vertically moving panel  71  moves in the direction of arrow d relative to the movable rails  14 . The first end  42   a  of the first arm  42  of the X arm  41  moves in the elongated hole  14   a  in the direction of arrow d, and the movable step  4  moves upward in the direction of arrow n. 
     When the movable step  4  comes to a position immediately before the upward movement-completed position, the pin  81  abuts against a slanting surface  72   e  of the hook  72  and rotates the hook  72  in the direction of arrow  1 . Since the pin  81  is disengaged from the slanting surface  72   e  at the position where the upward movement of the movable step  4  is completed, the hook  72  is rotated in the direction of arrow k by the spring  75 , and the operation panel  78  and the movable rails  14  are integrally connected to each other (see  FIGS. 43 and 44 ). 
     Next, when the slide lever  34  further rotates in the direction of arrow h from the upward movement-completed slide connection position (see  FIGS. 34 ,  40  and  46 ), the movable rails  14  are pushed and slid in the direction of arrow d. At this time, the movable step  4  connected to the movable rails  14  through the X arms  41  also slides in the direction of arrow d. However, since the hook  72  mounted on the vertically moving panel  71  is fitted to the pin  81  provided on the side surface of each movable rail  14 , the first end  42   a  of the first arm  42  of each X arm  41  connected to the vertically moving panel  71  cannot move relative to the movable rail  14 . Thus, the movable step  4  does not move downward in the direction of arrow m by its own weight. 
     As described above in detail, according to the present embodiment, the same advantages as those of the second embodiment can be obtained. 
     Fourth Embodiment 
     A fourth embodiment according to the present invention will be described below based on  FIGS. 50 to 52 . As a lock mechanism that connects and disconnects the movable rails  14  and the vertically moving panel  57  with and from each other, the fourth embodiment employs a structure that is different from that of the second embodiment is employed. Therefore, in the fourth embodiment, detailed explanation of the same portions as those of the second embodiment will be omitted. With the opening/closing operation of the slide door  2 , the slide lever  34  rotates, the movable step  4  moves forward or backward (projects or retracts), the vertically moving lever rotates, the vertically moving panel  57  moves and the movable step  4  moves vertically of course. 
     As shown in  FIGS. 50 to 52 , in the present embodiment, a vertically moving lever  86  that is rotatably connected to the plate cam bracket  100  (see  FIG. 22 ) includes a groove  86   a  in which the pin  63  is received. A hook  87  is rotatably connected to an upper surface of the vertically moving lever  86  through a pin  88 . The hook  87  has a groove  87   a  into which the pin  63  is fitted. 
     A lock lever  89  that limits rotation of the hook  87  is rotatably connected to an upper surface of the vertically moving lever  86  through a pin  90 . A spring  91  is provided between the hook  87  and the lock lever  89 . The hook  87  and the lock lever  89  are biased by a spring  91  in rotation directions respectively shown with arrows q and r such that the hook  87  and the lock lever  89  always pull each other. 
     Further, the hook  87  and the lock lever  89  respectively include pawls  87   b  and  89   a . The pawls  87   b  and  89   a  stop the rotation of the hook  87  in the direction of arrow q when the pin  63  enters the groove  87   a  and rotates the hook  87  in the direction of arrow p and the groove  87   a  is directed in a direction substantially perpendicular to a rotation direction of the vertically moving lever  86 . 
     A release actuator  92  is provided on an upper surface of the vertically moving lever  86 . The release actuator  92  is connected to the lock lever  89  and rotates the lock lever  89  in the direction of arrow s, thereby canceling the meshed state between the pawls  87   b  and  89   a . The release actuator  92  constitutes a lock release mechanism together with the hook  87  and the lock lever  89 , and eliminates an operation time lag caused by the groove  86   a  of the vertically moving lever  86  and an operation timing deviation with respect to the position of the slide door  2  at the time of the downward movement and at the time of the upward movement. 
     Here, action of the present embodiment will be described. 
     First, assume that the movable step  4  is in its accommodated state (see  FIG. 50 ). When the pin  63  enters the groove  87   a  of the hook  87  as the movable step  4  projects from this state, the hook  87  is pushed and rotated in the direction of arrow p. When the movable step  4  comes to a position where the slide projection is completed, the pawls  87   b  and  89   a  are meshed with each other by a force of the spring  91 . Since the pin  63  cannot rotate the hook  87  in the direction of arrow q, the pin  63  moves integrally with the vertically moving lever  86  (see  FIGS. 51 and 52 ) when the vertically moving lever  86  rotates in the direction of arrow g. 
     When it is necessary for the pin  63  to separate from the vertically moving lever  86  to accommodate the movable step  4 , the release actuator  92  rotates in the direction of arrow t, the lock lever  89  rotates in the direction of arrow s and the meshed state between the pawls  87   b  and  89   a  is cancelled. The hook  87  can rotate in the direction of arrow q, the pin  63  pushes the groove  87   a  and separates from the vertically moving lever  86 . Thereafter, when the operation of the release actuator  92  is cut, the hook  87  and the lock lever  89  return to their original states (see  FIG. 50 ) by a force of the spring  91 . 
     As described above in detail, according to the present embodiment, the same advantage as (1) of the second embodiment can be obtained. 
     Fifth Embodiment 
     A fifth embodiment according to the present invention will be described below based on  FIGS. 53 to 55 . The fifth embodiment is different from the first embodiment in that the fifth embodiment has a biasing member that biases the first ends  42   a  and  43   a  of both arms  42  and  43  connected to the movable rails  14  in a direction in which the first ends  42   a  and  43   a  separate from each other, i.e., in a direction in which the X arms  41  do not open. Detailed explanation of the same portions as those of the first embodiment will be omitted. 
     As shown in  FIGS. 53 to 55 , a plate-like mounting piece  14   b  is formed on an end of each movable rail  14  on the inner side of the vehicle (inner side in the widthwise direction of the vehicle). One end of a spring  151  as a biasing member is retained to the mounting piece  14   b . The other end of the spring  151  is retained to the vertically moving panel  45 . The spring  151  generates a biasing force in directions in which the mounting piece  14   b  and the vertically moving panel  45  approach each other. That is, the spring  151  biases the first end  42   a  of the first arm  42  of each X arm  41  connected to the movable rail  14  and the first end  43   a  of the second arm  43  connected to the movable rail  14  in a direction in which the first ends  42   a  and  43   a  separate from each other, i.e., in a direction in which the X arm  41  does not open. 
     The biasing force of the spring  151  is set greater than a force that pulls the first end  42   a  (vertically moving panel  45 ) of the first arm  42  by the weight of the movable step  4 . This prevents the height of the movable step  4  from lowering by an amount of backlash existing at various connections due to its own weight. More specifically, the backlashes are caused in gaps that are set in the X arm  41  and the vertically moving panel  45  relating to the operation of the movable step  4 , the vertically moving lever  37 , the lever  38 , the bush  39 , the movable rail  14 , the slide panel  15 , the slide lever  34 , the bush  35 , the plate cam  32 , the gear  30 , the opening/closing mechanism  29  (drive belt  28  and the like) and the like, or variations among the products. 
     Since the reduction in the height of the movable step  4  is suppressed, the movable step  4  can move forward and backward from or into the accommodation space S (entrance  3   a ) integrally with the movable rails  14  without interfering with the step panel  12 . 
     As described above in detail, according to the embodiment, the following advantages can be obtained in addition to the advantages (1) and (2) of the first embodiment. 
     (1) In the present embodiment, the first ends  42   a  and  43   a  of both arms  42  and  43  connected to the movable rails  14  are biased by the spring  151  in the direction in which the first ends  42   a  and  43   a  separate from each other, i.e., in the direction in which the X arm  41  does not open. Therefore, for example, it is possible to prevent the height of the movable step  4  from lowering due to its own weight by an amount of backlash of each movable rail  14  or each X arm  41  that supports the movable step  4  during the forward or backward movement of the movable rail  14 . Since the height of the movable rails  14  can be set without taking the backlashes of the X arms  41  and the movable rails  14  into account, the height of the movable rails  14  can be set lower, and the height of the movable step  4  after it is lowered can be set lower. 
     (2) Since it is possible to prevent the movable step  4  from lowering by its own weight, it is possible to prevent the movable step  4  from interfering with the step panel  12  during forward and backward integral movement with the movable rails  14 . 
     Sixth Embodiment 
     A sixth embodiment according to the present invention will be described below based on  FIG. 56 . The sixth embodiment is different from the fifth embodiment in that a biasing member that biases the X arm  41  in a direction in which the X arm  41  does not open is disposed on the movable step  4 . Detailed explanation of the same portions as those of the fifth embodiment will be omitted. 
       FIG. 56  is a plan view of the slide door  2  in its fully closed state (accommodated state of the movable step  4 ). As shown in  FIG. 56 , a peripheral edge of the movable step  4  is bent downward and an internal space S 1  is formed. A bracket  156  is fixed to the second end  42   b  of the first arm  42  of each X arm  41  in the internal space S 1 . Pulleys  157  are disposed at the outer edge of the movable step  4 . Specifically, the pulleys  157  are rotatably supported on both ends of the movable step  4  in the front-rear direction of the vehicle in the internal space S 1 . A cable  159  is round around each pulley  157 . One end of each cable  159  is retained to the spring  158  as the biasing member disposed in the internal space S 1 , and the other end of each cable  159  is retained to the bracket  156 . 
     The spring  158  transmits its biasing force to the second end  42   b  of the first arm  42  of each X arm  41  through the cable  159 , the pulley  157  and the bracket  156 . The spring  158  biases the second end  42   b  of the first arm  42  of the X arm  41  connected to the movable step  4  and the second end  43   b  of the second arm  43  connected to the movable step  4  in a direction in which the second ends  42   b  and  43   b  separate from each other, i.e., in a direction in which the X arm  41  does not open. 
     The biasing force of the spring  158  is set greater than a force that pulls the second end  42   b  of the first arm  42  by the weight of the movable step  4 . With this, the height of the movable step  4  is prevented from lowering due to its own weight by an amount of backlash existing in various connections. 
     As described above in detail, according to the present embodiment, the same advantages as those of the fifth embodiment can be obtained. 
     The above embodiments may be modified as follows. 
     In the fifth embodiment, as shown in  FIG. 57 , rollers  161  that project lower than the lowermost end of the movable step  4  and project inward of the vehicle than the end of the movable step  4  on the inner side of the vehicle (deeper side of the accommodation space S) may be disposed on both side surfaces of the movable step  4  in the front-rear direction of the vehicle, and a rolling surface  162  on which the rollers  161  roll as the movable rails  14  move forward and backward may be provided on the step panel  12  disposed on the lower side of each movable rail  14 . More specifically, each roller  161  is connected to the movable step  4  such that the roller  161  can rotate around an axis that matches with the rotation axis of the second end  43   b  of the second arm  43  of the X arm  41 , i.e., an axis of the second end  43   b  extending in a direction perpendicular to the longitudinal direction (forward and backward direction of the movable step  4 ) of the movable rails  14 . 
     By providing the rollers  161  disposed on the movable step  4  inward of the vehicle, the movable step  4  is supported by the rolling surface  162  through the rollers  161  when the movable step  4  moves forward and backward integrally with the movable rails  14 . That is, a gap between the lowermost end of the movable step  4  and the rolling surface  162  is determined in accordance with a projecting length of the roller  161  to the lower side of the movable step  4  irrespective of backlashes of the X arms  41  and the movable rails  14 . 
     According to the above structure, the same advantages as those of the fifth embodiment can be obtained. 
     Especially, even if a passenger treads on the movable step  4  during the forward/backward movement of the movable step  4  that is integral with the movable rails  14 , since the rollers  161  abut against the rolling surface  162  and receive the force, a sliding noise or an operation load caused by contact (e.g., metal contact) between the movable step  4  and the step panel  12  (rolling surface  162 ) is prevented from increasing. 
     Further, since the rollers  161  first abut against the end of the rolling surface  162  on the outer side of the vehicle, the movable step  4  can smoothly be guided into the accommodation space S even if the height of the movable step  4  is lowered due its own weight when the movable step  4  that is lifted by closing the X arms  41  is accommodated in the accommodation space S together with the movable rails  14 . 
     The same roller and rolling surface (roller  161  and rolling surface  162 ) as those of the above modification (see  FIG. 57 ) may be provided in the sixth embodiment. With this modified structure also, the same advantages as those of the modification can be obtained. 
     In each of the embodiments, an electric drive source (the slide door drive unit  21 ) for opening and closing the slide door  2  may be omitted. In this case also, it is possible to move the movable step  4  in synchronization with the manual opening and closing operations of the slide door  2 . 
     In each of the embodiments, the movement of the movable step  4  from its accommodated position to the projecting and descent position may be completed when the movement of the slide door  2  from its fully closed position to its fully opened position is completed.