Patent Publication Number: US-11643860-B2

Title: Vehicle door opening and closing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2019-0164178, filed on Dec. 10, 2019, in the Korean Intellectual Property Office, which application is hereby incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a vehicle door opening and closing apparatus. 
     BACKGROUND 
     Vehicles have door apertures for ingress and egress of vehicle passengers to and from a passenger compartment. A vehicle door is closed to block the door aperture and is opened to enable ingress and egress of passengers to and from the passenger compartment through the door aperture. Vehicle doors are divided into swing doors and sliding doors. The swing door is opened and closed by swinging around a hinge mounted between the swing door and the vehicle body. The sliding door is opened and closed by sliding a roller mounted on the sliding door along a rail mounted on the vehicle body. 
     The swing door is very easy to open and close, thereby enabling quick ingress and egress of passengers. However, when the swing door is opened, a space for ingress and egress is relatively small. When the vehicle is located in a narrow space, a swing trajectory of the door is not secured, which makes the opening and closing operation thereof difficult. 
     The sliding door is very easy to open and close even when the vehicle is located in a narrow space. When the sliding door is opened, a space for ingress and egress is relatively large. However, the sliding door requires relatively more force and time to open and close, which hinders quick ingress and egress of passengers. 
     According to the related art, as a vehicle door is operated by a single opening and closing method, it may be difficult to adequately respond to the needs of customers seeking ease of use, diversity, and novelty. 
     The above information described in this background section is provided to assist in understanding the background of the inventive concept, and may include any technical concept which is not considered as the prior art that is already known to those skilled in the art. 
     SUMMARY 
     Embodiments of the present disclosure solve problems occurring in the prior art while advantages achieved by the prior art are maintained intact. 
     The present disclosure relates to a vehicle door opening and closing apparatus. Particular embodiments relate to a vehicle door opening and closing apparatus allowing a vehicle door to open and close in one mode selected from a swing mode and a sliding mode, and more particularly to a vehicle door opening and closing apparatus allowing a center roller unit to be releasably connected to a vehicle door and a door frame of a vehicle body as either a swing mode or a sliding mode is selected, thereby reliably opening and closing the vehicle door in either the swing mode or the sliding mode. 
     An aspect of the present disclosure provides a vehicle door opening and closing apparatus allowing a vehicle door to open and close in one mode selected from a swing mode and a sliding mode, and more particularly, allowing a center roller unit to be releasably connected to the vehicle door and a door frame of a vehicle body as either the swing mode or the sliding mode is selected, thereby reliably opening and closing the vehicle door in either the swing mode or the sliding mode. 
     According to an aspect of the present disclosure, a vehicle door opening and closing apparatus may include a vehicle body having a door frame defining a door aperture, a vehicle door, a rail mounted on the vehicle body, a roller unit mounted on the vehicle door, moving along the rail, and allowing the vehicle door to open and close in one mode selected from a sliding mode and a swing mode, a center rail extending from an edge of the door aperture, a center roller unit including rollers guided along the center rail, a roller bracket having the rollers mounted thereon, a roller-side hinge element connected to the roller bracket, and a door-side hinge element rotatably connected to the roller-side hinge element by a hinge pin, a door-side docking unit releasably connecting the door-side hinge element to the vehicle door, and a frame-side docking unit releasably connecting the roller-side hinge element to the door frame. 
     The door-side docking unit may include a door-side bracket fixed to the vehicle door, a first door-side clamp member slidably mounted on the door-side bracket, and a second door-side clamp member opposite to the first door-side clamp member, and slidably mounted on the door-side bracket. 
     The first and second door-side clamp members may be movable in a direction approaching or moving away from the door-side bracket. 
     The first door-side clamp member may have a first door-side grip portion extending toward the second door-side clamp member, and the second door-side clamp member may have a second door-side grip portion extending toward the first door-side clamp member. 
     The door-side bracket may have a door-side cavity, the first door-side clamp member may have a first door-side rack portion movably received in the door-side cavity, the second door-side clamp member may have a second door-side rack portion movably received in the door-side cavity, and the first and second door-side rack portions may be moved by a door-side pinion. 
     The door-side pinion may be disposed between the first door-side rack portion and the second door-side rack portion, the first door-side rack portion may have first door-side rack teeth meshing with the door-side pinion, and the second door-side rack portion may have second door-side rack teeth meshing with the door-side pinion. 
     The frame-side docking unit may include a frame-side bracket fixed to the door frame, a first frame-side clamp member slidably mounted on the frame-side bracket, and a second frame-side clamp member opposite to the first frame-side clamp member, and slidably mounted on the frame-side bracket. 
     The first and second frame-side clamp members may be movable in a direction approaching or moving away from the frame-side bracket. 
     The first frame-side clamp member may have a first frame-side grip portion extending toward the second frame-side clamp member, and the second frame-side clamp member may have a second frame-side grip portion extending toward the first frame-side clamp member. 
     The frame-side bracket may have a frame-side cavity, the first frame-side clamp member may have a first frame-side rack portion movably received in the frame-side cavity, the second frame-side clamp member may have a second frame-side rack portion movably received in the frame-side cavity, and the first and second frame-side rack portions may be moved by a frame-side pinion. 
     The frame-side pinion may be disposed between the first frame-side rack portion and the second frame-side rack portion, the first frame-side rack portion may have first frame-side rack teeth meshing with the frame-side pinion, and the second frame-side rack portion may have second frame-side rack teeth meshing with the frame-side pinion. 
     The frame-side docking unit may have a guide projection, and the roller-side hinge element may have a guide hole into which the guide projection is inserted. 
     The door-side docking unit may include a door-side bracket fixed to the vehicle door, a first door-side clamp member pivotally mounted on the door-side bracket, and a second door-side clamp member opposite to the first door-side clamp member, and pivotally mounted on the door-side bracket. 
     The frame-side docking unit may include a frame-side bracket fixed to the door frame, a first frame-side clamp member pivotally mounted on the frame-side bracket, and a second frame-side clamp member opposite to the first frame-side clamp member, and pivotally mounted on the frame-side bracket. 
     The door-side docking unit may include a door-side bracket fixed to the vehicle door, a first door-side clamp member mounted on the door-side bracket in a manner that is biased toward a center of the door-side bracket by a first door-side biasing element, and a second door-side clamp member opposite to the first door-side clamp member, and mounted on the door-side bracket in a manner that is biased toward the center of the door-side bracket by a second door-side biasing element. 
     The frame-side docking unit may include a frame-side bracket fixed to the door frame, a first frame-side clamp member mounted on the frame-side bracket in a manner that is biased toward a center of the frame-side bracket by a first frame-side biasing element, and a second frame-side clamp member opposite to the first frame-side clamp member, and mounted on the frame-side bracket in a manner that is biased toward the center of the frame-side bracket by a second frame-side biasing element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of embodiments of the present disclosure will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    illustrates a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure, which is mounted on a rear door of a vehicle; 
         FIG.  2    illustrates a selector adjacent to an outside handle of a vehicle, an actuator and motors connected to the selector, and hold locks; 
         FIG.  3    illustrates a state in which the door of  FIG.  1    is opened in a sliding mode; 
         FIG.  4    illustrates a state in which the door of  FIG.  1    is opened in a swing mode; 
         FIG.  5    illustrates an operation in which an upper roller unit and a lower roller unit move along an upper rail and a lower rail in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  6    illustrates an upper roller unit and a lower roller unit in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  7    illustrates an operation in which a vehicle door is opened and closed in a swing mode by an upper roller unit and a lower roller unit of a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  8    illustrates an upper roller unit and a lower roller unit in a vehicle door opening and closing apparatus according to another exemplary embodiment of the present disclosure; 
         FIG.  9    illustrates an operation in which a vehicle door is opened and closed in a swing mode by an upper roller unit and a lower roller unit of a vehicle door opening and closing apparatus according to another exemplary embodiment of the present disclosure; 
         FIG.  10 A  illustrates a perspective view of an upper hold lock and a lower hold lock; 
         FIG.  10 B  illustrates a state in which an upper hold lock and a lower hold lock hold corresponding strikers; 
         FIG.  10 C  illustrates a state in which an upper hold lock and a lower hold lock release corresponding strikers; 
         FIG.  10 D  illustrates a state in which an upper hold lock and a lower hold lock are allowed to receive corresponding strikers; 
         FIG.  11    illustrates a main latch mounted on a vehicle door and a main striker; 
         FIG.  12    illustrates a perspective view of a center rail in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  13    illustrates a cross-sectional view of a swing guide of a center rail; 
         FIG.  14    illustrates a cross-sectional view of a sliding guide of a center rail; 
         FIG.  15    illustrates a structure in which a center roller unit is held in a swing guide of a center rail; 
         FIG.  16    illustrates an operation in which a center roller unit is released from a swing guide of a center rail; 
         FIG.  17    illustrates a center roller unit, a door-side docking unit, and a frame-side docking unit in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  18    illustrates a state in which a door-side hinge element of a center roller unit is connected to a door-side docking unit in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  19    illustrates a state in which a door-side hinge element of a center roller unit is released from a door-side docking unit in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  20    illustrates a cross-sectional view of a door-side docking unit according to an exemplary embodiment of the present disclosure; 
         FIG.  21    illustrates a state in which a roller-side hinge element of a center roller unit is connected to a frame-side docking unit in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  22    illustrates a cross-sectional view of a frame-side docking unit according to an exemplary embodiment of the present disclosure; 
         FIG.  23    illustrates a state in which a center roller unit is connected to a door-side docking unit and a frame-side docking unit in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  24    illustrates a state in which a center roller unit is connected to a door-side docking unit and the center roller unit is released from a frame-side docking unit in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  25    illustrates a state in which a vehicle door is opened and closed in a sliding mode in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  26    illustrates a state in which a center roller unit is connected to a frame-side docking unit and the center roller unit is released from a door-side docking unit in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  27    illustrates a state in which a vehicle door is opened and closed in a swing mode in a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure; 
         FIG.  28    illustrates a door-side docking unit according to another exemplary embodiment of the present disclosure; 
         FIG.  29    illustrates a frame-side docking unit according to another exemplary embodiment of the present disclosure; 
         FIG.  30    illustrates a door-side docking unit according to another exemplary embodiment of the present disclosure; 
         FIG.  31    illustrates a frame-side docking unit according to another exemplary embodiment of the present disclosure; 
         FIG.  32    illustrates a perspective view of a center rail in a vehicle door opening and closing apparatus according to another exemplary embodiment of the present disclosure; 
         FIG.  33    illustrates a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure, which is applied to a front door of a vehicle, in a state in which the front door is opened in a sliding mode; 
         FIG.  34    illustrates a state in which the front door of  FIG.  33    is opened in a swing mode; 
         FIG.  35    illustrates a vehicle door opening and closing apparatus according to an exemplary embodiment of the present disclosure, which is applied to a front door and a rear door of a vehicle, in a state in which the front door and the rear door are opened in a sliding mode; and 
         FIG.  36    illustrates a state in which the front door and the rear door of  FIG.  35    are opened in a swing mode. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals will be used throughout to designate the same or equivalent elements. In addition, a detailed description of well-known techniques associated with the present disclosure will be omitted in order not to unnecessarily obscure the gist of the present disclosure. 
     Terms such as first, second, A, B, (a), and (b) may be used to describe the elements in exemplary embodiments of the present disclosure. These terms are only used to distinguish one element from another element, and the intrinsic features, sequence or order, and the like of the corresponding elements are not limited by the terms. Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meanings as those generally understood by those with ordinary knowledge in the field of art to which the present disclosure belongs. Such terms as those defined in a generally used dictionary are to be interpreted as having meanings equal to the contextual meanings in the relevant field of art, and are not to be interpreted as having ideal or excessively formal meanings unless clearly defined as having such in the present application. 
     A vehicle door opening and closing apparatus, according to exemplary embodiments of the present disclosure, may allow a vehicle door to open and close selectively in either a sliding mode or a swing mode. In other words, the vehicle door opening and closing apparatus, according to exemplary embodiments of the present disclosure, may be a transform-type door opening and closing apparatus. The sliding mode may allow the vehicle door to open and close by sliding in a longitudinal direction of a vehicle, and the swing mode may allow the vehicle door to open and close by swinging inwards and outwards. 
     Referring to  FIG.  1   , a vehicle body  1  may have a plurality of door apertures  2  and  3 , and the plurality of door apertures  2  and  3  may be divided into a front aperture  2  and a rear aperture  3 . A plurality of vehicle doors  4  and  5  may include a front door  4  covering and uncovering the front aperture  2 , and a rear door  5  covering and uncovering the rear aperture  3 . As the front door  4  is opened, the front door  4  may uncover the front aperture  2 , and as the front door  4  is closed, the front door  4  may cover the front aperture  2 . As the rear door  5  is opened, the rear door  5  may uncover the rear aperture  3 , and as the rear door  5  is closed, the rear door  5  may cover the rear aperture  3 . 
     The vehicle door opening and closing apparatus, according to exemplary embodiments of the present disclosure, may be applied to the front door  4 , the rear door  5 , and the like.  FIGS.  1  to  16    illustrate a vehicle door opening and closing apparatus according to exemplary embodiments of the present disclosure, which is applied to the rear door  5 . Hereinafter, the rear door  5  will be referred to as the vehicle door  5 , and the rear aperture  3  will be referred to as the door aperture  3 . 
     The vehicle door opening and closing apparatus, according to exemplary embodiments of the present disclosure, may include one or more rails  11  and  12  mounted on the vehicle body  1 , and the rails  11  and  12  may extend in the longitudinal direction of the vehicle. Referring to  FIG.  1   , an upper rail  11  may be mounted on an upper edge of the vehicle body  1 , and a lower rail  12  may be mounted on a lower edge of the vehicle body  1 . The upper rail  11  and the lower rail  12  may extend in the longitudinal direction of the vehicle. The upper rail  11  may be disposed on an upper edge of the door aperture  3 , and the lower rail  12  may be disposed on a lower edge of the door aperture  3 . 
     The vehicle door opening and closing apparatus, according to exemplary embodiments of the present disclosure, may include roller units  21  and  22  guided along the rails  11  and  12 . The roller units  21  and  22  may allow the vehicle door  5  to open and close in one mode selected from the sliding mode and the swing mode. In particular, the roller units  21  and  22  may be releasably held in predetermined positions of the rails  11  and  12  by hold locks  31  and  32 . Specifically, when the roller units  21  and  22  are held in the predetermined positions of the rails  11  and  12  by the hold locks  31  and  32 , the vehicle door  5  may be opened and closed in the swing mode in which the vehicle door swings in the predetermined positions of the rails  11  and  12 . When the roller units  21  and  22  are released by the hold locks  31  and  32 , the vehicle door  5  may be opened and closed in the sliding mode in which the vehicle door slides along the rails  11  and  12 . 
     Referring to  FIGS.  1  and  3   , an upper roller unit  21  may be mounted on an upper end of the vehicle door  5 , and the upper roller unit  21  may slide along the upper rail  11 . A lower roller unit  22  may be mounted on a lower end of the vehicle door  5 , and the lower roller unit  22  may slide along the lower rail  12 . 
     Referring to  FIG.  2   , the vehicle door  5  may include an outside handle  6 , and a selector  40  for selecting the sliding mode and the swing mode may be adjacent to the outside handle  6 . The selector  40  may have a first switch  41  selecting the sliding mode, and a second switch  42  selecting the swing mode. 
     When a user presses the first switch  41  and the sliding mode is selected, the vehicle door  5  may slide along the upper rail  11 , the lower rail  12 , and a center rail  13  as illustrated in  FIG.  3    as the user pushes or pulls the outside handle  6  toward the front or rear of the vehicle. In the sliding mode, the vehicle door  5  may move between a first open position OP 1  and a first closed position CP 1 , as illustrated in  FIGS.  1  and  3   . The first open position OP 1  refers to a position in which the vehicle door  5  is fully opened, and the first closed position CP 1  refers to a position in which the vehicle door  5  is fully closed. 
     When the user presses the second switch  42  and the swing mode is selected, the vehicle door  5  may swing as illustrated in  FIG.  4    as the user pushes or pulls the outside handle  6  toward a passenger compartment or the exterior side of the vehicle. In the swing mode, the vehicle door  5  may move between a second open position OP 2  in which the vehicle door  5  is fully opened and a second closed position CP 2  in which the vehicle door  5  is fully closed, as illustrated in  FIGS.  7  and  9   . In particular, when the vehicle door  5  is held in the first closed position CP 1 , it may be operated in the swing mode. 
     The upper roller unit  21  may have an upper hold lock  31 , and the vehicle body  1  may have a first upper striker  31   a  and a second upper striker  31   b  protruding downwardly from a roof of the vehicle body  1 . The first upper striker  31   a  may be aligned with or adjacent to a virtual axis of the first closed position CP 1 , and the second upper striker  31   b  may be aligned with or adjacent to a virtual axis of the first open position OP 1 . 
     According to an exemplary embodiment, as illustrated in  FIGS.  1  and  3   , the upper hold lock  31  may releasably hold the first upper striker  31   a  in the first closed position CP 1 , and releasably hold the second upper striker  31   b  in the first open position OP 1 . That is, one upper hold lock  31  may selectively hold the first upper striker  31   a  and the second upper striker  31   b . As the upper hold lock  31  holds the first upper striker  31   a , the upper roller unit  21  may be held in the first closed position CP 1 . As the upper hold lock  31  holds the second upper striker  31   b , the upper roller unit  21  may be held in the first open position OP 1 . 
     According to another exemplary embodiment, the upper hold lock  31  may releasably hold the first upper striker  31   a  in the first closed position CP 1 , and a separate upper open hold lock (not shown) may releasably hold the second upper striker  31   b  in the first open position OP 1 . That is, the upper hold lock  31 , which releasably holds the first upper striker  31   a  in the first closed position CP 1 , and the upper open hold lock, which releasably holds the second upper striker  31   b  in the first open position OP 1 , may be individually mounted on the upper roller unit  21 . 
     Referring to  FIGS.  4  and  9   , the upper roller unit  21  may have an upper rotation axis CX 1 , and the vehicle door  5  may rotate around the upper rotation axis CX 1 . When the upper roller unit  21  is firmly held in the first closed position CP 1  by the upper hold lock  31  and the first upper striker  31   a , the vehicle door  5  may rotate around the upper rotation axis CX 1 . 
     The lower roller unit  22  may have a lower hold lock  32 , and the vehicle body  1  may have a first lower striker  32   a  and a second lower striker  32   b  protruding upwardly from the bottom of the vehicle body  1 . The first lower striker  32   a  may be aligned with or adjacent to the virtual axis of the first closed position CP 1 , and the second lower striker  32   b  may be aligned with or adjacent to the virtual axis of the first open position OP 1 . 
     According to an exemplary embodiment, as illustrated in  FIGS.  1  and  3   , the lower hold lock  32  may releasably hold the first lower striker  32   a  in the first closed position CP 1 , and releasably hold the second lower striker  32   b  in the first open position OP 1 . That is, one lower hold lock  32  may selectively hold the first lower striker  32   a  and the second lower striker  32   b . As the lower hold lock  32  holds the first lower striker  32   a , the lower roller unit  22  may be firmly held in the first closed position CP 1 . As the lower hold lock  32  holds the second lower striker  32   b , the lower roller unit  22  may be firmly held in the first open position OP 1 . 
     According to another exemplary embodiment, the lower hold lock  32  may releasably hold the first lower striker  32   a  in the first closed position CP 1 , and a separate lower open hold lock (not shown) may releasably hold the second lower striker  32   b  in the first open position OP 1 . That is, the lower hold lock  32 , which releasably holds the first lower striker  32   a  in the first closed position CP 1 , and the lower open hold lock, which releasably holds the second lower striker  32   b  in the first open position OP 1 , may be individually mounted on the lower roller unit  22 . 
     Referring to  FIGS.  4  and  9   , the lower roller unit  22  may have a lower rotation axis CX 2 , and the vehicle door  5  may rotate around the lower rotation axis CX 2 . When the lower roller unit  22  is firmly held in the first closed position CP 1  by the lower hold lock  32  and the first lower striker  32   a , the vehicle door  5  may rotate around the lower rotation axis CX 2 . 
     As illustrated in  FIG.  4   , the upper rotation axis CX 1  and the lower rotation axis CX 2  may be vertically aligned, and the vehicle door  5  may rotate around the vertically aligned upper and lower rotation axes CX 1  and CX 2 . 
     Referring to  FIG.  2   , the selector  40  may be electrically connected to an actuator  43 , and the actuator  43  may be configured to operate the upper hold lock  31  and the lower hold lock  32 . 
     As the user selects the selector  40 , the actuator  43  may selectively perform a hold operation in which the upper hold lock  31  holds the first upper striker  31   a  and the lower hold lock  32  holds the first lower striker  32   a , and a release operation in which the upper hold lock  31  releases the first upper striker  31   a  and the lower hold lock  32  releases the first lower striker  32   a.    
     When the user presses the first switch  41  of the selector  40  in a state in which the vehicle door  5  is closed, the upper hold lock  31  may release the first upper striker  31   a  and the lower hold lock  32  may release the first lower striker  32   a  simultaneously by the release operation of the actuator  43 . Thus, the user may slide the vehicle door  5  in the longitudinal direction of the vehicle body  1  so that the vehicle door  5  may be opened and closed in the sliding mode. 
     When the user presses the second switch  42  of the selector  40  in a state in which the vehicle door  5  is closed, the upper hold lock  31  may hold the first upper striker  31   a  and the lower hold lock  32  may hold the first lower striker  32   a  simultaneously by the hold operation of the actuator  43 , and the upper roller unit  21  and the lower roller unit  22  may be firmly held in the first closed position CP 1 . Thus, the user may swing the vehicle door  5  toward the interior space or exterior of the vehicle so that the vehicle door  5  may be opened and closed in the swing mode. 
     According to an exemplary embodiment, as illustrated in  FIG.  2   , one actuator  43  may operate the upper hold lock  31  and the lower hold lock  32  simultaneously. 
     According to another exemplary embodiment, an actuator operating the upper hold lock  31  and another actuator operating the lower hold lock  32  may be individually connected to the selector  40 . 
       FIGS.  10 A to  10 D  illustrate the upper hold lock  31  and the lower hold lock  32  according to an exemplary embodiment of the present disclosure. Referring to  FIGS.  10 A to  10 D , each of the upper hold lock  31  and the lower hold lock  32  may include a catch  71 , a pawl  72  releasably engaging with the catch  71 , and a lever  73  operatively connected to the pawl  72 . The lever  73  may be connected to the actuator  43  through a cable  75 . As the cable  75  is reversed (pulled) by the actuator  43 , the catch  71  may release the strikers  31   a  and  32   a . A portion of the catch  71 , the pawl  72 , and the lever  73  may be covered by a cover plate  76 , and the cover plate  76  may be attached to a mounting plate  74 . The strikers  31   a  and  32   a  may be fixed to the vehicle body  1  by a mounting plate  78 . 
     Referring to  FIGS.  10 A to  10 D , the upper hold lock  31  may releasably hold the first upper striker  31   a , and the lower hold lock  32  may releasably hold the first lower striker  32   a.    
     The catch  71  may be pivotally mounted on the mounting plate  74  through a first pivot shaft  71   a . The catch  71  may have a slot  71   b  receiving the strikers  31   a  and  32   a , and the catch  71  may engage with or release the strikers  31   a  and  32   a . The catch  71  may move between an engaging position (see  FIG.  10 B ) and a release position (see  FIG.  10 C ). The engaging position refers to a position in which the catch  71  engages with the strikers  31   a  and  32   a  as illustrated in  FIG.  10 B , and the release position refers to a position in which the catch  71  releases the strikers  31   a  and  32   a  as illustrated in  FIG.  10 C . When the catch  71  is in the engaging position as illustrated in  FIG.  10 B , the catch  71  may engage with the strikers  31   a  and  32   a  so that the catch  71  may hold the strikers  31   a  and  32   a . When the catch  71  is in the release position as illustrated in  FIG.  10 C , the catch  71  may release the strikers  31   a  and  32   a . Thus, the strikers  31   a  and  32   a  may be released from the slot  71   b  of the catch  71  or be received in the slot  71   b  of the catch  71 . The catch  71  may be biased toward the release position by a first biasing element  71   c  such as a torsion spring. The first biasing element  71   c  may be disposed around the first pivot shaft  71   a . The catch  71  may have a locking shoulder  71   d.    
     The pawl  72  may be pivotally mounted on the mounting plate  74  through a second pivot shaft  72   a , and the pawl  72  may move between a pawl locking position (see  FIG.  10 B ) and a pawl release position (see  FIGS.  10 C and  10 D ). The pawl locking position refers to a position in which the pawl  72  engages with the catch  71  and the catch  71  is kept in the engaging position, and the pawl release position refers to a position in which the pawl  72  releases the catch  71  and the catch  71  is allowed to move from the engaging position to the release position. As illustrated in  FIG.  10 B , when the pawl  72  is in the pawl locking position, the movement (rotation) of the catch  71  may be restricted by the pawl  72  so that the catch  71  may be kept in the engaging position. As illustrated in  FIGS.  10 C and  10 D , when the pawl  72  is in the pawl release position, the movement (rotation) of the catch  71  may not be restricted by the pawl  72  so that the catch  71  may move from the engaging position to the release position. The pawl  72  may be biased toward the pawl locking position (see  FIG.  10 B ) by a second biasing element  72   c  such as a torsion spring. The second biasing element  72   c  may be disposed around the second pivot shaft  72   a.    
     The pawl  72  may have a locking projection  72   d  locked to the locking shoulder  71   d  of the catch  71 . As illustrated in  FIG.  10 B , as the pawl  72  is moved to the pawl locking position by the second biasing element  72   c , the locking projection  72   d  of the pawl  72  may be locked to the locking shoulder  71   d  of the catch  71  and the movement (rotation) of the catch  71  may be restricted, so that the catch  71  may be kept in the engaging position. As illustrated in  FIG.  10 C , as the pawl  72  is moved to the pawl release position by the lever  73 , the locking projection  72   d  of the pawl  72  may be released from the locking shoulder  71   d  of the catch  71  and the movement (rotation) of the catch  71  may be allowed, so that the catch  71  may be moved to the release position by the first biasing element  71   c.    
     The lever  73  may be pivotally mounted on the mounting plate  74  through a third pivot shaft  73   a . The lever  73  may be connected to the actuator  43  through the cable  75 . An end of the cable  75  may be fixed to the lever  73 , and the cable  75  may be advanced or reversed by the actuator  43 . As the actuator  43  moves the cable  75 , the lever  73  may pivot around the third pivot shaft  73   a . As the cable  75  is reversed, the lever  73  may move the pawl  72  to the pawl release position (see  FIG.  10 C ). 
     The lever  73  may be operatively connected to the pawl  72  through a pin  72   b  and an opening  73   b . The pin  72   b  may be provided on the pawl  72 , and the opening  73   b  may be provided in the lever  73 . The pin  72   b  may be movably received in the opening  73   b . As the lever  73  pivots around the third pivot shaft  73   a , the pin  72   b  may move in the opening  73   b , allowing the pawl  72  to move. 
     As illustrated in  FIG.  10 B , when the cable  75  is advanced by the actuator  43 , the locking projection  72   d  of the pawl  72  may be locked to the locking shoulder  71   d  of the catch  71  and the movement (rotation) of the catch  71  may be restricted so that the catch  71  may be kept in the engaging position. The strikers  31   a  and  32   a  may be held in the slot  71   b  of the catch  71 . That is, the upper hold lock  31  and the lower hold lock  32  may hold the corresponding strikers  31   a  and  32   a.    
     As illustrated in  FIG.  10 C , when the cable  75  is reversed by the actuator  43 , the lever  73  may move the pawl  72  to the pawl release position. The locking projection  72   d  of the pawl  72  may be released from the locking shoulder  71   d  of the catch  71  and the movement (rotation) of the catch  71  may be allowed, so that the catch  71  may be moved to the release position by the first biasing element  71   c , and the strikers  31   a  and  32   a  may be released from the slot  71   b  of the catch  71 . Thus, the upper hold lock  31  and the lower hold lock  32  may release the corresponding strikers  31   a  and  32   a , and the upper roller unit  21  and the lower roller unit  22  may slide along the upper rail  11  and the lower rail  12 . 
     As illustrated in  FIG.  10 D , even though the cable  75  is advanced by the actuator  43  in a state in which the locking projection  72   d  of the pawl  72  is released from the locking shoulder  71   d  of the catch  71 , the catch  71  may be kept in the release position by the first biasing element  71   c  so that the movement (rotation) of the catch  71  may be allowed. In this state, the strikers  31   a  and  32   a  may be allowed to be received in the slot  71   b  of the catch  71 . That is, in a state in which the movement (rotation) of the catch  71  is allowed as the locking projection  72   d  of the pawl  72  is released from the locking shoulder  71   d  of the catch  71 , when the upper roller unit  21  and the lower roller unit  22  slide between the first closed position CP 1  and the first open position OP 1 , the strikers  31   a  and  32   a  may be allowed to be received in the slot  71   b  of the catch  71 . When a force applied by the upper hold lock  31  and the lower hold lock  32  in a state in which the strikers  31   a  and  32   a  are received in the slot  71   b  of the catch  71  is greater than a spring force of the first biasing element  71   c , the catch  71  may be moved to the engaging position. As illustrated in  FIG.  10 B , as the locking projection  72   d  of the pawl  72  is locked to the locking shoulder  71   d  of the catch  71 , the catch  71  may hold the strikers  31   a  and  32   a.    
     Referring to  FIG.  5   , each of the upper rail  11  and the lower rail  12  may be mounted on the vehicle body  1  through a mounting bracket  15 , and the mounting bracket  15  may have a shape corresponding to that of the upper rail  11  and the lower rail  12 . Each of the upper rail  11  and the lower rail  12  may have a first extension portion  51  extending straightly in the longitudinal direction of the vehicle, and a second extension portion  52  extending from the first extension portion  51  toward the interior space of the vehicle. The second extension portion  52  may be bent with respect to the first extension portion  51  at a predetermined angle. 
     Referring to  FIG.  6   , each of the upper roller unit  21  and the lower roller unit  22  may include a roller bracket  64  having rollers  65  and  66  rolling along the rails  11  and  12 , and a body  60  connecting the roller bracket  64  and the vehicle door  5 . 
     The body  60  may extend diagonally so as not to contact the first extension portion  51  and the second extension portion  52 . The body  60  may have a first end portion  61  facing the interior side of the vehicle, and a second end portion  62  facing the exterior side of the vehicle. The first end portion  61  of the body  60  may be attached to the roller bracket  64 , and the second end portion  62  of the body  60  may be attached to the vehicle door  5 . 
     The roller bracket  64  may rotatably support the rollers  65  and  66 , and the rollers  65  and  66  may roll along the upper rail  11  and the lower rail  12 . As illustrated in  FIG.  6   , a middle roller  65  and two side rollers  66  disposed on both sides of the middle roller  65  may be rotatably mounted on the roller bracket  64 . A rotation axis of the middle roller  65  may be perpendicular to a rotation axis of the side roller  66 . 
     According to an exemplary embodiment, as illustrated in  FIG.  6   , the first end portion  61  of the body  60  may be pivotally connected to the roller bracket  64  through a pivot pin  68 , and the second end portion  62  of the body  60  may be fixed to the vehicle door  5 . Thus, the vehicle door  5  may swing around the pivot pin  68  adjacent to the roller bracket  64 . The body  60  may have a pivot lug  63  protruding from the first end portion  61  toward the roller bracket  64 , and the roller bracket  64  may be connected to the pivot lug  63  through the pivot pin  68 . The roller bracket  64  may be shaped so as not to interfere with the body  60  when the vehicle door  5  swings. The upper rotation axis CX 1  and the lower rotation axis CX 2  may be defined by the pivot pin  68 . For example, the upper rotation axis CX 1  and the lower rotation axis CX 2  may be a virtual axis extending vertically along a center point of the pivot pin  68 , and the upper rotation axis CX 1  and the lower rotation axis CX 2  may be vertically aligned, so that the vehicle door  5  may swing around the vertical rotation axis that virtually connects the upper rotation axis CX 1  and the lower rotation axis CX 2 . The upper hold lock  31  may be fixed to the roller bracket  64  of the upper roller unit  21 , and the lower hold lock  32  may be fixed to the roller bracket  64  of the lower roller unit  22 . 
     When, by the hold operation of the actuator  43 , the upper hold lock  31  firmly holds the roller bracket  64  of the upper roller unit  21  in the first closed position CP 1  and the lower hold lock  32  firmly holds the roller bracket  64  of the lower roller unit  22  in the first closed position CP 1 , the vehicle door  5  may swing around the upper rotation axis CX 1  of the upper roller unit  21  and the lower rotation axis CX 2  of the lower roller unit  22  as illustrated in  FIG.  7   . The vehicle door  5  may move between the second closed position CP 2  in which the vehicle door  5  is closed and the second open position OP 2  in which the vehicle door  5  is opened. When the vehicle door  5  swings, the other adjacent door  4  or other components may be spaced apart from the vehicle door  5  by a predetermined gap S 1  so that any interference with the door  4  or the other components may be prevented. For example, the vehicle door  5  may be a rear door, and the other adjacent door  4  may be a front door. 
     According to the exemplary embodiment illustrated in  FIGS.  6  and  7   , as the pivot pin  68  is located between the roller bracket  64  and the first end portion  61  of the body  60 , the rotation axes CX 1  and CX 2  of the vehicle door  5  may be relatively far from the vehicle door  5 . Since a swing trajectory T 1  and a rotation radius R 1  of the vehicle door  5  are relatively increased, the gap S 1  between the vehicle door  5  and the other adjacent door  4  may be relatively increased. If the gap S 1  between the vehicle door  5  and the other adjacent door  4  is reduced, the vehicle door  5  may interfere with the adjacent door  4  when the vehicle door  5  moves toward the second open position OP 2 , and an open space created by the swing of the vehicle door  5  may be relatively narrowed since the swing trajectory T 1  of the vehicle door  5  is relatively reduced. 
     According to another exemplary embodiment, as illustrated in  FIGS.  8  and  9   , the first end portion  61  of the body  60  may be fixed to the roller bracket  64 , and the second end portion  62  of the body  60  may be pivotally connected to the vehicle door  5  through a pivot pin  68   a . Thus, the vehicle door  5  may swing around the pivot pin  68   a  adjacent to the second end portion  62  of the body  60 . 
     Referring to  FIGS.  8  and  9   , the roller bracket  64  may be fixed to the first end portion  61  of the body  60  by welding, using fasteners, and/or the like, and the second end portion  62  of the body  60  may be pivotally connected to the vehicle door  5  through the pivot pin  68   a . The vehicle door  5  may have a pivot lug  69  protruding toward the body  60 , and the pivot lug  69  may be pivotally connected to the second end portion  62  of the body  60  through the pivot pin  68   a . The second end portion  62  of the body  60  may be shaped so as not to interfere with the vehicle door  5  when the vehicle door  5  swings. The upper rotation axis CX 1  and the lower rotation axis CX 2  may be defined by the pivot pin  68   a . For example, the upper rotation axis CX 1  and the lower rotation axis CX 2  may be a virtual axis extending vertically along a center point of the pivot pin  68   a , and the upper rotation axis CX 1  and the lower rotation axis CX 2  may be vertically aligned, so that the vehicle door  5  may swing around the vertical rotation axis that virtually connects the upper rotation axis CX 1  and the lower rotation axis CX 2 . The upper hold lock  31  may be fixed to the body  60  of the upper roller unit  21 , and the lower hold lock  32  may be fixed to the body  60  of the lower roller unit  22 . 
     Referring to  FIG.  9   , when the upper hold lock  31  firmly holds the roller bracket  64  of the upper roller unit  21  in the first closed position CP 1 , and the lower hold lock  32  firmly holds the roller bracket  64  of the lower roller unit  22  in the first closed position CP 1 , the vehicle door  5  may swing around the upper rotation axis CX 1  of the upper roller unit  21  and the lower rotation axis CX 2  of the lower roller unit  22 . Thus, the vehicle door  5  may move between the second closed position CP 2  in which the vehicle door  5  is closed and the second open position OP 2  in which the vehicle door  5  is opened. 
     According to the exemplary embodiment illustrated in  FIGS.  8  and  9   , as the pivot pin  68   a  is located between the second end portion  62  of the body  60  and the vehicle door  5 , the rotation axes CX 1  and CX 2  of the vehicle door  5  may be relatively close to the vehicle door  5 . Since a rotation radius R 2  of the vehicle door  5  is relatively shortened, a gap S 2  between the vehicle door  5  and the other adjacent door  4  may be relatively reduced, resulting in improved exterior styling. Even though the rotation axes CX 1  and CX 2  of the vehicle door  5  are close to the vehicle door  5 , a swing trajectory T 2  of the vehicle door  5  is not reduced, and thus an open space created by the swing of the vehicle door  5  may not be narrowed. 
     Referring to  FIG.  11   , a main latch  80  may be mounted on a rear end of the vehicle door  5 , and a main striker  81  may be fixed to the vehicle body  1 . The main latch  80  may releasably engage with the main striker  81 . When the vehicle door  5  is in the first closed position CP 1  or the second closed position CP 2 , the main latch  80  may engage with the main striker  81  by an engaging operation of the outside handle  6  so that the vehicle door  5  may be locked in the first closed position CP 1  or the second closed position CP 2 . When the vehicle door  5  is in the first closed position CP 1  or the second closed position CP 2 , the main latch  80  may release the main striker  81  by a release operation of the outside handle  6  so that the vehicle door  5  may be allowed to move in the sliding mode or the swing mode. When the vehicle door  5  is held in the first closed position CP 1  and the main latch  80  releases the main striker  81 , a center roller unit  23  may be released from the center rail  13 , and thus the vehicle door  5  may be opened and closed in the swing mode. 
     The vehicle door opening and closing apparatus, according to exemplary embodiments of the present disclosure, may further include the center rail  13  mounted at a central portion of the vehicle body  1 , and the center roller unit  23  guided along the center rail  13 . 
     Referring to  FIGS.  1  and  3   , the center rail  13  may extend from a rear edge of the door aperture  3  in the longitudinal direction of the vehicle. The center roller unit  23  may be pivotally mounted at a central portion of the vehicle door  5 . In particular, the center roller unit  23  may be mounted in a position adjacent to the rear end of the vehicle door  5 . The center roller unit  23  may be guided along the center rail  13 . 
     Referring to  FIG.  12   , the center rail  13  may include a sliding guide  91  extending straightly in the longitudinal direction of the vehicle, and a swing guide  92  extending from the sliding guide  91  toward the interior side of the vehicle. The swing guide  92  may be bent at a predetermined angle with respect to the sliding guide  91  through a bending portion  93 , and the bending portion  93  may be curved at a predetermined radius. 
     Referring to  FIGS.  13  to  15   , the center roller unit  23  may include a roller bracket  101  and rollers  105  and  106  rotatably mounted on the roller bracket  101 . The roller bracket  101  may be pivotally mounted at the central portion of the vehicle door  5 . The rollers  105  and  106  may roll along the center rail  13 . As illustrated in  FIG.  15   , a middle roller  105  and two side rollers  106  disposed on both sides of the middle roller  105  may be rotatably mounted on the roller bracket  101 . A rotation axis of the middle roller  10  may be perpendicular to a rotation axis of the side roller  106 . 
     When the vehicle door  5  slides in the longitudinal direction of the vehicle as the sliding mode is selected, the sliding guide  91  may guide the rollers  105  and  106  of the center roller unit  23 . 
     Referring to  FIGS.  12  and  14   , the sliding guide  91  may include a stopper wall  95  preventing the rollers  105  and  106  of the center roller unit  23  from being separated from the sliding guide  91 . The stopper wall  95  may extend along a length of the sliding guide  91  and a length of the bending portion  93 . The stopper wall  95  may protrude vertically downward from the top of the sliding guide  91 . As the stopper wall  95  closes an upper area of the sliding guide  91  and an upper area of the bending portion  93 , the rollers  105  and  106  of the center roller unit  23  may be prevented from moving away from the sliding guide  91  toward the exterior side of the vehicle as illustrated in  FIG.  14   . 
     When the vehicle door  5  is opened and closed in the swing mode as the swing mode is selected, the swing guide  92  may guide the rollers  105  and  106  of the center roller unit  23  to be released from the center rail  13 . 
     An exterior side of the swing guide  92  may be entirely opened toward the exterior of the vehicle. A guide projection  94  may protrude upwardly from the bottom of the swing guide  92 , and the guide projection  94  may extend along a length of the swing guide  92 . When the vehicle door  5  swings from the second closed position CP 2  to the second open position OP 2  along the swing trajectory T 1  or T 2 , the middle roller  105  of the center roller unit  23  may be guided along the guide projection  94  as illustrated in  FIG.  13   . 
     A front end  95   a  of the stopper wall  95  of the sliding guide  91  and a rear end  94   a  of the guide projection  94  may be located so as not to interfere with the swing trajectories T 1  and T 2  of the vehicle door  5 . In addition, as illustrated in  FIG.  16   , an axis X 1  of the sliding guide  91  and an axis X 2  of the swing guide  92  may intersect at a predetermined angle a. In particular, the angle a of intersection between the axis X 1  of the sliding guide  91  and the axis X 2  of the swing guide  92  may be an obtuse angle, so that the rollers  105  and  106  of the center roller unit  23  may easily be released from the swing guide  92  of the center rail  13  or may easily be received in the swing guide  92  of the center rail  13 . The center rail  13  may include a space  98  allowing the rollers  105  and  106  of the center roller unit  23  to be released from the center rail  13  or be received in the center rail  13  when the vehicle door  5  swings in the swing mode. The space  98  may be defined between the front end  95   a  of the stopper wall  95  and the rear end  94   a  of the guide projection  94  as the front end  95   a  of the stopper wall  95  and the rear end  94   a  of the guide projection  94  are spaced apart from each other. Due to the space  98 , there is no interference when the rollers  105  and  106  of the center roller unit  23  are released from the center rail  13  or are received in the center rail  13  in the swing mode. 
     Meanwhile, according to the exemplary embodiment illustrated in  FIGS.  12  to  16   , when malfunction of the main latch  80  or deformation of the vehicle door  5  or the swing guide  92  due to an external impact occurs in the sliding mode, the rollers  105  and  106  of the center roller unit  23  may be separated from the center rail  13 , and thus the vehicle door  5  may fail to be easily opened and closed in the sliding mode. 
     In order to deal with this problem, the vehicle door opening and closing apparatus, according to exemplary embodiments of the present disclosure, may include a door-side docking unit  130  releasably connecting the center roller unit  23  to the vehicle door  5 , and a frame-side docking unit  140  releasably connecting the center roller unit  23  to a door frame  3   a  of the vehicle body as illustrated in  FIG.  17   . Accordingly, the rollers  105  and  106  of the center roller unit  23  may not be separated from the center rail  13  in any mode of the swing mode and the sliding mode, and the center roller unit  23  may be releasably connected to the vehicle door  5  and the door frame  3   a  of the vehicle body as either the swing mode or the sliding mode is selected, and thus the vehicle door opening and closing apparatus may reliably open and close the vehicle door  5  in either the swing mode or the sliding mode. Here, the door frame  3   a  refers to a frame area of the vehicle body defining the door aperture  3 . 
     Referring to  FIG.  32   , according to another exemplary embodiment, the swing guide  92  of the center rail  13  may have a stopper wall  99  extending from the stopper wall  95  of the sliding guide  91 , and the swing guide  92  may use the stopper wall  99  to prevent the rollers  105  and  106  of the center roller unit  23  from being separated from the center rail  13 . Thus, the rollers  105  and  106  of the center roller unit  23  may not be separated from the center rail  13  in any mode of the swing mode and the sliding mode. 
     The center roller unit  23  may include a roller-side hinge element  110  connected to the roller bracket  101  of the center roller unit  23 , and a door-side hinge element  120  rotatably connected to the roller-side hinge element  110  through a hinge pin  150 . 
     The roller-side hinge element  110  may be integrally connected to the roller bracket  101  of the center roller unit  23 . In particular, the roller-side hinge element  110  may be integrally formed with the roller bracket  101  so that the roller-side hinge element  110  and the roller bracket  101  may form a unitary one-piece structure. The roller-side hinge element  110  may include a roller-side base  115  integrally connected to the roller bracket  101  of the center roller unit  23 , and a pair of roller-side hinge arms  111  extending from the roller-side base  115 . The roller-side hinge element  110  may be releasably connected to the door frame  3   a  by the frame-side docking unit  140 . 
     The door-side hinge element  120  may include a door-side base  125  and a pair of door-side hinge arms  121  extending from the door-side base  125 . The door-side hinge arms  121  may be rotatably connected to the roller-side hinge arms  111  through the hinge pin  150 . The door-side hinge element  120  may be releasably connected to the vehicle door  5  by the door-side docking unit  130 . 
     Referring to  FIGS.  18  to  20   , according to an exemplary embodiment, the door-side docking unit  130  may include a door-side bracket  135  and first and second door-side clamp members  131  and  132  which are movable in a direction approaching or moving away from the door-side bracket  135 . The first door-side clamp member  131  and the second door-side clamp member  132  may move opposite to each other with respect to the door-side bracket  135  so that they may symmetrically clamp or release both edges of the door-side base  125  of the door-side hinge element  120 . 
     The door-side bracket  135  may be fixed to the vehicle door  5  by welding, using fasteners, and/or the like. The door-side bracket  135  may have a door-side cavity  135   a.    
     The first door-side clamp member  131  may be slidably mounted on the door-side bracket  135 . The first door-side clamp member  131  may include a first door-side grip portion  133  and a first door-side extension portion  133   a  extending toward the second door-side clamp member  132 . The first door-side grip portion  133  and the first door-side extension portion  133   a  may be spaced apart from each other. 
     The first door-side grip portion  133  may releasably clamp the door-side base  125  of the door-side hinge element  120 . In particular, the first door-side grip portion  133  may have a shape corresponding to that of one edge of the door-side base  125 . One surface of the door-side bracket  135  may be fixed to the vehicle door  5  by welding, using fasteners, and/or the like. The first door-side grip portion  133  may be spaced apart from the other surface of the door-side bracket  135  by a predetermined gap t 1 . The gap t 1  between the other surface of the door-side bracket  135  and a surface of the first door-side grip portion  133  facing the door-side bracket  135  may correspond to a thickness of the door-side base  125 , and thus the door-side base  125  may be firmly clamped by the door-side bracket  135  and the first door-side grip portion  133 . 
     The first door-side extension portion  133   a  may be movably received in the door-side cavity  135   a  of the door-side bracket  135 . A first door-side rack portion  137  may extend from the first door-side extension portion  133   a  toward the second door-side clamp member  132 , and the first door-side rack portion  137  may have first door-side rack teeth  137   a  arranged in a longitudinal direction of the first door-side rack portion  137 . 
     As illustrated in  FIG.  18   , as the first door-side clamp member  131  moves to approach the door-side bracket  135 , the first door-side grip portion  133  may clamp one edge of the door-side base  125  of the door-side hinge element  120 . As illustrated in  FIG.  19   , as the first door-side clamp member  131  moves away from the door-side bracket  135 , the first door-side grip portion  133  may release one edge of the door-side base  125  of the door-side hinge element  120 . 
     The second door-side clamp member  132  may be slidably mounted on the door-side bracket  135 . The second door-side clamp member  132  may include a second door-side grip portion  134  and a second door-side extension portion  134   a  extending toward the first door-side clamp member  131 . The second door-side grip portion  134  and the second door-side extension portion  134   a  may be spaced apart from each other. 
     The second door-side grip portion  134  may releasably clamp the door-side base  125  of the door-side hinge element  120 . In particular, the second door-side grip portion  134  may have a shape corresponding to that of the other edge of the door-side base  125 . The second door-side grip portion  134  may be spaced apart from the other surface of the door-side bracket  35  by the predetermined gap t 1 . The gap t 1  between the other surface of the door-side bracket  135  and a surface of the second door-side grip portion  134  facing the door-side bracket  135  may correspond to the thickness of the door-side base  125 , and thus the door-side base  125  may be firmly clamped by the door-side bracket  135  and the second door-side grip portion  134 . 
     The second door-side extension portion  134   a  may be movably received in the door-side cavity  135   a  of the door-side bracket  135 . A second door-side rack portion  138  may extend from the second door-side extension portion  134   a  toward the first door-side clamp member  131 . The second door-side rack portion  138  may have second door-side rack teeth  138   a  arranged in a longitudinal direction of the second door-side rack portion  138 . 
     A door-side pinion  139  may be disposed between the first door-side rack portion  137  and the second door-side rack portion  138 . The door-side pinion  139  may mesh with the first door-side rack teeth  137   a  and the second door-side rack teeth  138   a.    
     The door-side pinion  139  may engage with a driving shaft of a first driving motor  151 , and the first driving motor  151  may be a bidirectional motor rotatable in both directions. The door-side pinion  139  may be rotatable in both directions by the first driving motor  151 . 
     Referring to  FIG.  2   , the first driving motor  151  may be electrically connected to the selector  40 . The first driving motor  151  may change its rotation direction as the sliding mode or the swing mode is selected by the first switch  41  or the second switch  42  of the selector  40 , and thus the first door-side clamp member  131  and the second door-side clamp member  132  may clamp or release the door-side base  125  of the door-side hinge element  120 . 
     When the sliding mode is selected by the first switch  41  of the selector  40 , the first door-side clamp member  131  and the second door-side clamp member  132  may move toward the door-side bracket  135  by a forward rotation (clockwise rotation) of the first driving motor  151  as illustrated in  FIG.  18   , and thus the first door-side grip portion  133  of the first door-side clamp member  131  and the second door-side grip portion  134  of the second door-side clamp member  132  may clamp the door-side base  125  of the door-side hinge element  120 . 
     When the swing mode is selected by the second switch  42  of the selector  40 , the first door-side clamp member  131  and the second door-side clamp member  132  may move away from the door-side bracket  135  by a reverse rotation (counterclockwise rotation) of the first driving motor  151  as illustrated in  FIG.  19   , and thus the first door-side grip portion  133  of the first door-side clamp member  131  and the second door-side grip portion  134  of the second door-side clamp member  132  may release the door-side base  125  of the door-side hinge element  120 . 
     Referring to  FIGS.  21  and  22   , according to an exemplary embodiment, the frame-side docking unit  140  may include a frame-side bracket  145  and first and second frame-side clamp members  141  and  42  which are movable in a direction approaching or moving away from the frame-side bracket  145 . The first frame-side clamp member  141  and the second frame-side clamp member  142  may move opposite to each other with respect to the frame-side bracket  145  so that they may symmetrically clamp or release both edges of the roller-side base  115  of the roller-side hinge element  110 . 
     The frame-side bracket  145  may be fixed to the door frame  3   a  by welding, using fasteners, and/or the like. The frame-side bracket  145  may have a first frame-side cavity  145   a.    
     The first frame-side clamp member  141  may include a first frame-side grip portion  143  and a first frame-side extension portion  143   a  extending toward the second frame-side clamp member  142 . The first frame-side grip portion  143  and the first frame-side extension portion  143   a  may be spaced apart from each other. 
     The first frame-side grip portion  143  may releasably clamp the roller-side base  115  of the roller-side hinge element  110 . In particular, the first frame-side grip portion  143  may have a shape corresponding to that of one edge of the roller-side base  115 . One surface of the frame-side bracket  145  may be fixed to the door frame  3   a  by welding, using fasteners, and/or the like. The first frame-side grip portion  143  may be spaced apart from the other surface of the frame-side bracket  145  by a predetermined gap t 2 . The gap t 2  between the other surface of the frame-side bracket  145  and a surface of the first frame-side grip portion  143  facing the frame-side bracket  145  may correspond to a thickness of the roller-side base  115 , and thus one edge of the roller-side base  115  may be firmly clamped by the frame-side bracket  145  and the first frame-side grip portion  143 . 
     The first frame-side extension portion  143   a  may be movably received in the first frame-side cavity  145   a  of the frame-side bracket  145 . A first frame-side rack portion  147  may extend from the first frame-side extension portion  143   a  toward the second frame-side clamp member  142 , and the first frame-side rack portion  147  may have first frame-side rack teeth  147   a  arranged in a longitudinal direction of the first frame-side rack portion  147 . 
     As the first frame-side clamp member  141  moves to approach the frame-side bracket  145 , the first frame-side grip portion  143  may clamp one edge of the roller-side base  115  of the roller-side hinge element  110 . As the first frame-side clamp member  141  moves away from the frame-side bracket  145 , the first frame-side grip portion  143  may release one edge of the roller-side base  115  of the roller-side hinge element  110 . 
     The second frame-side clamp member  142  may include a second frame-side grip portion  144  and a second frame-side extension portion  144   a  extending toward the first frame-side clamp member  141 . The second frame-side grip portion  144  and the second frame-side extension portion  144   a  may be spaced apart from each other. 
     The second frame-side grip portion  144  may releasably clamp the roller-side base  115  of the roller-side hinge element  110 . In particular, the second frame-side grip portion  144  may have a shape corresponding to that of the other edge of the roller-side base  115 . 
     The second frame-side grip portion  144  may be spaced apart from the other surface of the frame-side bracket  145  by the predetermined gap t 2 . The gap t 2  between the other surface of the frame-side bracket  145  and a surface of the second frame-side grip portion  144  facing the frame-side bracket  145  may correspond to the thickness of the roller-side base  115 , and thus the other edge of the roller-side base  115  may be firmly clamped by the frame-side bracket  145  and the second frame-side grip portion  144 . 
     The second frame-side extension portion  144   a  may be movably received in the first frame-side cavity  145   a  of the frame-side bracket  145 . A second frame-side rack portion  148  may extend from the second frame-side extension portion  14   a  toward the first frame-side clamp member  141 , and the second frame-side rack portion  148  may have second frame-side rack teeth  148   a  arranged in a longitudinal direction of the second frame-side rack portion  148 . 
     A frame-side pinion  149  may be disposed between the first frame-side rack portion  147  and the second frame-side rack portion  148 . The frame-side pinion  149  may mesh with the first frame-side rack teeth  147   a  of the first frame-side rack portion  147  and the second frame-side rack teeth  148   a  of the second frame-side rack portion  148 . 
     The frame-side pinion  149  may engage with a driving shaft of a second driving motor  152 , and the second driving motor  152  may be a bidirectional motor rotatable in both directions. The frame-side pinion  149  may be rotatable in both directions by the second driving motor  152 . 
     Referring to  FIG.  2   , the second driving motor  152  may be electrically connected to the selector  40 . The second driving motor  152  may change its rotation direction as the sliding mode or the swing mode is selected by the first switch  41  or the second switch  42  of the selector  40 , and thus the first frame-side clamp member  141  and the second frame-side clamp member  142  may clamp or release the roller-side base  115  of the roller-side hinge element  110 . 
     When the sliding mode is selected by the first switch  41  of the selector  40 , the first frame-side clamp member  141  and the second frame-side clamp member  142  may move toward the frame-side bracket  145  by a forward rotation (clockwise rotation) of the second driving motor  152  as illustrated in  FIG.  21   , and thus the first frame-side grip portion  143  of the first frame-side clamp member  141  and the second frame-side grip portion  144  of the second frame-side clamp member  142  may clamp the roller-side base  115  of the roller-side hinge element  110 . 
     When the swing mode is selected by the second switch  42  of the selector  40 , the first frame-side clamp member  141  and the second frame-side clamp member  142  may move away from the frame-side bracket  145  by a reverse rotation (counterclockwise rotation) of the second driving motor  152 , and thus the first frame-side grip portion  143  of the first frame-side clamp member  141  and the second frame-side grip portion  144  of the second frame-side clamp member  142  may release the roller-side base  115  of the roller-side hinge element  110 . 
     Referring to  FIG.  21   , the roller-side base  115  of the roller-side hinge element  110  may have a guide hole  15   a , and the frame-side bracket  145  of the frame-side docking unit  140  may have a guide projection  145   b . When the roller-side hinge element  110  is clamped to the frame-side docking unit  140 , the guide projection  145   b  of the frame-side bracket  145  may be inserted into the guide hole  15   a  of the roller-side base  115 , and thus the roller-side hinge element  110  may not only be aligned with the frame-side bracket  145  of the frame-side docking unit  140 , but also be more firmly clamped to the frame-side bracket  145  of the frame-side docking unit  140 . 
     Referring to  FIG.  23   , when the vehicle door  5  is closed, the door-side hinge element  120  of the center roller unit  23  may be connected to the vehicle door  5  by the door-side docking unit  130 , and the roller-side hinge element  110  of the center roller unit  23  may be connected to the door frame  3   a  by the frame-side docking unit  140  so that the vehicle door  5  may be kept in a closed state. 
     When the sliding mode is selected by the first switch  41  of the selector  40 , the first and second frame-side clamp members  141  and  142  of the frame-side docking unit  140  may release the roller-side hinge element  110  of the center roller unit  23  and the first and second door-side clamp members  131  and  132  of the door-side docking unit  130  may clamp the door-side hinge element  120  of the center roller unit  23  as illustrated in  FIG.  24   . Then, the vehicle door  5  may be allowed to open and close in the sliding mode as illustrated in  FIG.  25   . 
     When the swing mode is selected by the second switch  42  of the selector  40 , the first and second door-side clamp members  131  and  132  of the door-side docking unit  130  may release the door-side hinge element  120  of the center roller unit  23  and the first and second frame-side clamp members  141  and  142  of the frame-side docking unit  140  may clamp the roller-side hinge element  110  of the center roller unit  23  as illustrated in  FIG.  26   . Then, the vehicle door  5  may be allowed to open and close in the swing mode as illustrated in  FIG.  26   . 
       FIG.  28    illustrates a door-side docking unit  230  according to another exemplary embodiment of the present disclosure. 
     Referring to  FIG.  28   , the door-side docking unit  230  may include a door-side bracket  235 , a first door-side clamp member  231  pivotally mounted on one side of the door-side bracket  235  through a first door-side pivot pin  233 , and a second door-side clamp member  232  pivotally mounted on the other side of the door-side bracket  235  through a second door-side pivot pin  234 . 
     The door-side bracket  235  may be fixed to the vehicle door  5  by welding, using fasteners, and/or the like. The door-side bracket  235  may have a seat surface  236  supporting the door-side base  125  of the door-side hinge element  120 . 
     The first door-side clamp member  231  and the second door-side clamp member  232  may move opposite to each other with respect to the door-side bracket  235 . 
     The first door-side clamp member  231  may have a first door-side grip surface  237 . When the first door-side clamp member  231  pivots toward the door-side bracket  235 , the first door-side grip surface  237  may grip one edge of the door-side base  125 . The second door-side clamp member  232  may have a second door-side grip surface  238 . When the second door-side clamp member  232  pivots toward the door-side bracket  235 , the second door-side grip surface  238  may grip the other edge of the door-side base  125 . 
     As indicated by a solid line in  FIG.  28   , as the first door-side clamp member  231  and the second door-side clamp member  232  pivot toward the door-side bracket  235 , the door-side base  125  of the door-side hinge element  120  may be clamped by the first door-side clamp member  231  and the second door-side clamp member  232 . 
     As indicated by a dotted line in  FIG.  28   , as the first door-side clamp member  231  and the second door-side clamp member  232  pivot away from the door-side bracket  235 , the door-side base  125  of the door-side hinge element  120  may be released from the first door-side clamp member  231  and the second door-side clamp member  232 . 
     According to an exemplary embodiment, the first door-side clamp member  231  may be rotated by a first driving motor  251 , and the second door-side clamp member  232  may be rotated by a second driving motor  252 . 
     According to another exemplary embodiment, the first door-side clamp member  231  and the second door-side clamp member  232  may be rotated by a single driving motor. For example, the first door-side pivot pin  233  and the second door-side pivot pin  234  may be connected to a single driving motor through a transmission mechanism such as a belt drive or a gear train. The transmission mechanism may be configured to individually transmit power of one driving motor to the first door-side pivot pin  233  of the first door-side clamp member  231  and the second door-side pivot pin  234  of the second door-side clamp member  232 . 
     Since the other configurations and operations in these exemplary embodiments are similar to or the same as those in the preceding exemplary embodiments, a detailed description thereof will be omitted. 
       FIG.  29    illustrates a frame-side docking unit  240  according to another exemplary embodiment of the present disclosure. 
     Referring to  FIG.  29   , the frame-side docking unit  240  may include a frame-side bracket  245 , a first frame-side clamp member  241  pivotally mounted on one side of the frame-side bracket  245  through a first frame-side pivot pin  243 , and a second frame-side clamp member  242  pivotally mounted on the other side of the frame-side bracket  245  through a second frame-side pivot pin  244 . 
     The frame-side bracket  245  may be fixed to the door frame  3   a  by welding, using fasteners, and/or the like. The frame-side bracket  245  may have a seat surface  246  supporting the roller-side base  115  of the roller-side hinge element  110 . 
     The first frame-side clamp member  241  and the second frame-side clamp member  242  may move opposite to each other with respect to the frame-side bracket  245 . 
     The first frame-side clamp member  241  may have a first frame-side grip surface  247 . When the first frame-side clamp member  241  pivots toward the frame-side bracket  245 , the first frame-side grip surface  247  may grip one edge of the roller-side base  115 . The second frame-side clamp member  242  may have a second frame-side grip surface  248 . When the second frame-side clamp member  242  pivots toward the frame-side bracket  245 , the second frame-side grip surface  248  may grip the other edge of the roller-side base  115 . 
     As indicated by a solid line in  FIG.  29   , as the first frame-side clamp member  241  and the second frame-side clamp member  242  pivot toward the frame-side bracket  245 , the roller-side base  115  of the roller-side hinge element  110  may be clamped by the first frame-side clamp member  241  and the second frame-side clamp member  242 . 
     As indicated by a dotted line in  FIG.  29   , as the first frame-side clamp member  241  and the second frame-side clamp member  242  pivot away from the frame-side bracket  245 , the roller-side base  115  of the roller-side hinge element  110  may be released from the first frame-side clamp member  241  and the second frame-side clamp member  242 . 
     According to an exemplary embodiment, the first frame-side clamp member  241  may be rotated by a third driving motor  261 , and the second door-side clamp member  242  may be rotated by a fourth driving motor  262 . 
     According to another exemplary embodiment, the first frame-side clamp member  241  and the second frame-side clamp member  242  may be rotated by a single driving motor. For example, the first frame-side pivot pin  243  and the second frame-side pivot pin  244  may be connected to a single driving motor through a transmission mechanism such as a belt drive or a gear train. The transmission mechanism may be configured to individually transmit power of one driving motor to the first frame-side pivot pin  243  of the first frame-side clamp member  241  and the second frame-side pivot pin  244  of the second frame-side clamp member  242 . 
     Since the other configurations and operations in these exemplary embodiments are similar to or the same as those in the preceding exemplary embodiments, a detailed description thereof will be omitted. 
     Referring to  FIG.  30   , according to another exemplary embodiment, a door-side docking unit  330  may include a door-side bracket  335 , a first door-side clamp member  331  mounted on one side of the door-side bracket  335  in a manner that is biased toward the center of the door-side bracket  335  by a first door-side biasing element  333 , and a second door-side clamp member  332  mounted on the other side of the door-side bracket  335  in a manner that is biased toward the center of the door-side bracket  335  by a second door-side biasing element  334 . 
     The door-side bracket  335  may be fixed to the vehicle door  5  by welding, using fasteners, and/or the like. The door-side bracket  335  may have a first door-side sidewall  351  and a second door-side sidewall  352  spaced apart from each other, and the door-side base  125  of the door-side hinge element  120  may be received between the first door-side sidewall  351  and the second door-side sidewall  352 . The first door-side sidewall  351  may have a first door-side guide recess  353  receiving the first door-side biasing element  333  and guiding the movement of the first door-side clamp member  331 . The second door-side sidewall  352  may have a second door-side guide recess  354  receiving the second door-side biasing element  334  and guiding the movement of the second door-side clamp member  332 . 
     The first door-side clamp member  331  may have a first door-side grip surface  337 . As the first door-side clamp member  331  moves on a surface of the door-side base  125  which is to come into contact with the first door-side grip surface  337 , the first door-side grip surface  337  may releasably grip one edge of the door-side base  125 . The second door-side clamp member  332  may have a second door-side grip surface  338 . As the second door-side clamp member  332  moves on the surface of the door-side base  125  which is to come into contact with the second door-side grip surface  338 , the second door-side grip surface  338  may releasably grip the other edge of the door-side base  125 . 
     As the first door-side clamp member  331  and the second door-side clamp member  332  move toward the center of the door-side bracket  335 , the first door-side clamp member  331  and the second door-side clamp member  332  may press the door-side base  125  of the door-side hinge element  120 , and thus the door-side base  125  of the door-side hinge element  120  may be clamped by the first door-side clamp member  331  and the second door-side clamp member  332 . 
     As the first door-side clamp member  331  and the second door-side clamp member  332  move away from the door-side bracket  335 , the first door-side grip surface  337  of the first door-side clamp member  331  and the second door-side grip surface  338  of the second door-side clamp member  332  may be spaced apart from the door-side base  125  of the door-side hinge element  120 , and thus the door-side base  125  of the door-side hinge element  120  may be released from the first door-side clamp member  331  and the second door-side clamp member  332 . 
     The first door-side clamp member  331  may be moved by a driving means such that it may be received in the first door-side guide recess  353 , and the second door-side clamp member  332  may be moved by a driving means such that it may be received in the second door-side guide recess  354 . For example, the first door-side clamp member  331  may be moved toward the first door-side sidewall  351  by a driving means such as a linear motor, and the second door-side clamp member  332  may be moved toward the second door-side sidewall  352  by a driving means such as a linear motor. As the first door-side clamp member  331  overcomes a force of the first door-side biasing element  333  and is received in the first door-side guide recess  353 , and the second door-side clamp member  332  overcomes a force of the second door-side biasing element  334  and is received in the second door-side guide recess  354 , the door-side base  125  of the door-side hinge element  120  may be released from the first door-side clamp member  331  and the second door-side clamp member  332 . 
     Since the other configurations and operations in this exemplary embodiment are similar to or the same as those in the preceding exemplary embodiments, a detailed description thereof will be omitted. 
     Referring to  FIG.  31   , according to another exemplary embodiment, a frame-side docking unit  340  may include a frame-side bracket  345 , a first frame-side clamp member  341  mounted on one side of the frame-side bracket  345  in a manner that is biased toward the center of the frame-side bracket  345  by a first frame-side biasing element  343 , and a second frame-side clamp member  342  mounted on the other side of the frame-side bracket  345  in a manner that is biased toward the center of the frame-side bracket  345  by a second frame-side biasing element  344 . 
     The frame-side bracket  345  may be fixed to the door frame  3   a  by welding, using fasteners, and/or the like. The frame-side bracket  345  may have a first frame-side sidewall  361  and a second frame-side sidewall  362  spaced apart from each other, and the roller-side base  115  of the roller-side hinge element  110  may be received between the first frame-side sidewall  361  and the second frame-side sidewall  362 . The first frame-side sidewall  361  may have a first frame-side guide recess  363  receiving the first frame-side biasing element  343  and guiding the movement of the first frame-side clamp member  341 . The second frame-side sidewall  362  may have a second frame-side guide recess  364  receiving the second frame-side biasing element  344  and guiding the movement of the second frame-side clamp member  342 . 
     The first frame-side clamp member  341  may have a first frame-side grip surface  347 . As the first frame-side clamp member  341  moves on a surface of the roller-side base  115  which is to come into contact with the first frame-side grip surface  347 , the first frame-side grip surface  347  may releasably grip one edge of the roller-side base  115 . The second frame-side clamp member  342  may have a second frame-side grip surface  348 . As the second frame-side clamp member  342  moves on the surface of the roller-side base  115  which is to come into contact with the second frame-side grip surface  348 , the second frame-side grip surface  348  may releasably grip the other edge of the roller-side base  115 . 
     As the first frame-side clamp member  341  and the second frame-side clamp member  342  move toward the center of the frame-side bracket  345 , the first frame-side clamp member  341  and the second frame-side clamp member  342  may press the roller-side base  115  of the roller-side hinge element  110 , and thus the roller-side base  115  of the roller-side hinge element  110  may be clamped by the first frame-side clamp member  341  and the second frame-side clamp member  342 . 
     As the first frame-side clamp member  341  and the second frame-side clamp member  342  move away from the frame-side bracket  345 , the first frame-side grip surface  347  of the first frame-side clamp member  341  and the second frame-side grip surface  348  of the second frame-side clamp member  342  may be spaced apart from the roller-side base  115  of the roller-side hinge element  110 , and thus the roller-side base  115  of the roller-side hinge element  110  may be released from the first frame-side clamp member  341  and the second frame-side clamp member  342 . 
     The first frame-side clamp member  341  may be moved by a driving means such that it may be received in the first frame-side guide recess  363 , and the second frame-side clamp member  342  may be moved by a driving means such that it may be received in the second frame-side guide recess  364 . For example, the first frame-side clamp member  341  may be moved toward the first frame-side sidewall  361  by a driving means such as a linear motor, and the second frame-side clamp member  342  may be moved toward the second frame-side sidewall  362  by a driving means such as a linear motor. As the first frame-side clamp member  341  overcomes a force of the first frame-side biasing element  343  and is received in the first frame-side guide recess  363 , and the second frame-side clamp member  342  overcomes a force of the second frame-side biasing element  344  and is received in the second frame-side guide recess  364 , the roller-side base  115  of the roller-side hinge element  110  may be released from the first frame-side clamp member  341  and the second frame-side clamp member  342 . 
     Since the other configurations and operations in this exemplary embodiment are similar to or the same as those in the preceding exemplary embodiments, a detailed description thereof will be omitted. 
       FIGS.  1  to  32    illustrate the vehicle door opening and closing apparatus according to exemplary embodiments of the present disclosure applied to the rear door  5 . However, the vehicle door opening and closing apparatus according to exemplary embodiments of the present disclosure may be applied to various vehicle doors, such as front doors, in addition to rear doors. 
       FIGS.  33  and  34    illustrate the vehicle door opening and closing apparatus according to exemplary embodiments of the present disclosure applied to the front door  4 .  FIG.  33    illustrates a state in which the front door  4  is opened in the sliding mode, and  FIG.  34    illustrates a state in which the front door  4  is opened in the swing mode. 
       FIGS.  35  and  36    illustrate the vehicle door opening and closing apparatus according to exemplary embodiments of the present disclosure applied to both the front door  4  and the rear door  5 .  FIG.  35    illustrates a state in which the front door  4  and the rear door  5  are opened in the sliding mode, and  FIG.  36    illustrates a state in which the front door  4  and the rear door  5  are opened in the swing mode. 
     As set forth above, the vehicle door opening and closing apparatus according to exemplary embodiments of the present disclosure may perform the opening and closing operations of the vehicle door by selectively switching the sliding mode and the swing mode, thereby meeting the needs of customers such as convenience and diversity. In addition, it may select the opening and closing operations of the vehicle door by taking the customer&#39;s situation and environment into consideration, thereby improving convenience and quality. 
     In particular, the vehicle door opening and closing apparatus may allow the center roller unit to be releasably connected to the vehicle door and the door frame of the vehicle body as either the swing mode or the sliding mode is selected, thereby reliably opening and closing the vehicle door in either the swing mode or the sliding mode. 
     In terms of vehicle specifications, the vehicle door opening and closing structure may be standardized, regardless of vehicle models. Thus, the manufacturing cost and investment cost may be significantly reduced. 
     Hereinabove, although the present disclosure has been described with reference to exemplary embodiments and the accompanying drawings, the present disclosure is not limited thereto, but may be variously modified and altered by those skilled in the art to which the present disclosure pertains without departing from the spirit and scope of the present disclosure claimed in the following claims.