Patent Publication Number: US-2022216641-A1

Title: Connector

Description:
INCORPORATION BY REFERENCE 
     This application is based upon and claims the benefit of priority from Japanese patent application No. 2021-1241, filed on Jan. 7, 2021, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     The present disclosure relates to a connector. 
     Patent Literature 1 (Published Japanese Translation of PCT International Publication for patent application, No. 2016-511520) discloses an electrical connector assembly that includes a shield housing  101  having a plurality of receptacle carrier receiving cavities  100 , and a plurality of receptacle carriers (not shown) to be respectively inserted into the plurality of receptacle carrier receiving cavities  100  as shown in  FIG. 41  of the present application. The inner wall surface of each of the receptacle carrier receiving cavities  100  has a projecting part  102 . When each of the receptacle carriers is inserted into each of the receptacle carrier receiving cavities  100  in this structure, a plurality of terminals accommodated in each of the receptacle carriers are secondarily locked by the projecting part  102 . 
     SUMMARY 
     However, in the structure of Patent Literature 1 described above, when inserting each receptacle carrier into the corresponding receptacle carrier receiving cavity  100 , it is necessary to pay close attention not to insert each receptacle carrier into another receptacle carrier receiving cavity  100  that is different from the corresponding receptacle carrier receiving cavity  100 . In other words, the problem of wrong insertion that inserts each receptacle carrier into another receptacle carrier receiving cavity  100  that is not the corresponding receptacle carrier receiving cavity  100  has been occurring. 
     An object of the present disclosure is to provide a technique that prevents each internal housing from being inserted into a cavity different from a corresponding cavity when inserting a plurality of internal housings into a plurality of cavities formed in an external housing. 
     A connector according to an embodiment includes an external housing including a plurality of cavities and a plurality of internal housings to be respectively inserted into the plurality of cavities, each internal housing accommodating a plurality of terminals, wherein a retainer extending in a housing insertion direction of inserting each of the internal housings into each of the cavities is formed on an inner wall surface of each of the cavities, a groove part for receiving the retainer when each of the internal housings is inserted into each of the cavities is formed on an outer wall surface of each of the internal housings, when each of the internal housings is inserted into each of the cavities, the retainer is inserted into the groove part, and thereby the plurality of terminals accommodated in each of the internal housings are secondarily locked by the retainer, the retainers of the plurality of cavities have different shapes from one another, and the groove parts of the plurality of internal housings have shapes complementary to the shapes of the retainers of corresponding cavities. 
     This prevents each internal housing from being inserted into a cavity different from a corresponding cavity when inserting a plurality of internal housings into a plurality of cavities formed in an external housing. 
     The above and other objects, features and advantages of the present disclosure will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of an external housing in which internal housings are accommodated; 
         FIG. 2  is a perspective view of the external housing in which the internal housings are not accommodated; 
         FIG. 3  is a perspective view of three internal housings; 
         FIG. 4  is a perspective view of the three internal housings viewed from a different direction; 
         FIG. 5  is a perspective view of the three internal housings viewed from another different direction; 
         FIG. 6  is a front view of the external housing in which the internal housings are accommodated; 
         FIG. 7  is a front view of the external housing in which the internal housings are not accommodated; 
         FIG. 8  is a view showing retainers of a first cavity; 
         FIG. 9  is a view showing retainers of a second cavity; 
         FIG. 10  is a view showing retainers of a third cavity; 
         FIG. 11  is a left side view of a first internal housing; 
         FIG. 12  is a left side view of a second internal housing; 
         FIG. 13  is a left side view of a third internal housing; 
         FIG. 14  is a right side view of the first internal housing; 
         FIG. 15  is a right side view of the second internal housing; 
         FIG. 16  is a right side view of the third internal housing; 
         FIG. 17  is a view showing an example of the cross section of the first internal housing stored in the first cavity on the back side; 
         FIG. 18  is a view showing an example of the cross section of the first internal housing stored in the first cavity on the front side; 
         FIG. 19  is a view showing an example of the cross section of the second internal housing stored in the second cavity on the back side; 
         FIG. 20  is a view showing an example of the cross section of the second internal housing stored in the second cavity on the front side; 
         FIG. 21  is a view showing an example of the cross section of the third internal housing stored in the third cavity on the back side; 
         FIG. 22  is a view showing an example of the cross section of the third internal housing stored in the third cavity on the front side; 
         FIG. 23  is a view showing the case where the first internal housing is about to be inserted into the second cavity; 
         FIG. 24  is a view showing the case where the first internal housing is about to be inserted into the third cavity; 
         FIG. 25  is a view showing the case where the second internal housing is about to be inserted into the first cavity; 
         FIG. 26  is a view showing the case where the second internal housing is about to be inserted into the third cavity; 
         FIG. 27  is a view showing the case where the third internal housing is about to be inserted into the first cavity; 
         FIG. 28  is a view showing the case where the third internal housing is about to be inserted into the second cavity. 
         FIG. 29  is a view showing a first terminal that is crimped onto a first wire; 
         FIG. 30  is a view showing a second terminal that is crimped onto a second wire; 
         FIG. 31  is a view showing the state where the first internal housing into which the first terminal is inserted is inserted into the external housing; 
         FIG. 32  is a view showing the first terminal inserted into the first internal housing and the retainers of the external housing; 
         FIG. 33  is a view showing the first terminal inserted into the second internal housing and the retainers of the external housing; 
         FIG. 34  is a view showing the first terminal inserted into the third internal housing and the retainers of the external housing; 
         FIG. 35  is a view showing the second terminal inserted into the first internal housing and the retainers of the external housing; 
         FIG. 36  is a view showing the second terminal inserted into the second internal housing and the retainers of the external housing; 
         FIG. 37  is a view showing the second terminal inserted into the third internal housing and the retainers of the external housing; 
         FIG. 38  is a view showing the state where the first terminal is not completely inserted; 
         FIG. 39  is a view showing the state where the external housing is warped when a retainer does not have a hook shape; 
         FIG. 40  is a view showing an example of the state where the occurrence of warpage is prevented by a force acting to warp the external housing and a hook shape of a retainer; and 
         FIG. 41  is view of a simplified version of FIG. 2 in Patent literature 1. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present disclosure will be described hereinafter with reference to the drawings. As shown in  FIG. 1 , a connector  1  includes an external housing  2  in which cavities  11 ,  12 , and  13  are formed, and a plurality of internal housings  3 ,  4 , and  5  to be accommodated in the external housing  2 . As described later, the number of cavities formed in the external housing  2  is three. 
     The internal housings  3 ,  4 , and  5  are accommodated in the cavities  11 ,  12 , and  13 , respectively. The internal housing  3  is accommodated in the cavity  11 . The internal housing  4  is accommodated in the cavity  12 . The internal housing  5  is accommodated in the cavity  13 . 
     Thus, the cavity corresponding to the internal housing  3  is the cavity  11 . The cavity corresponding to the internal housing  4  is the cavity  12 . The cavity corresponding to the internal housing  5  is the cavity  13 . 
       FIG. 1  is a perspective view of the external housing  2  in the state where the internal housings  3 ,  4 , and  5  are accommodated in the external housing  2 , and  FIG. 2  is a perspective view of the external housing  2  in the state where the internal housings  3 ,  4 , and  5  are not accommodated in the external housing  2 . Note that, in  FIG. 1  and other figures, wires  41  and  43  are partly not shown for better visibility of the figures. 
     The shape of the first internal housing  3 , the shape of the second internal housing  4 , and the shape of the third internal housing  5  are similar to but different from one another.  FIGS. 3 and 4  are perspective view of the internal housings  3 ,  4 , and  5 , and  FIG. 5  is a perspective view of the internal housings  3 ,  4 , and  5  viewed from below. 
     For example, as shown in  FIGS. 3, 4, and 5 , the internal housings  3 ,  4 , and  5  have holes  3   d ,  3   e ,  4   d ,  4   e ,  5   d , and  5   e  for insertion of terminals attached to wires. Particularly, as shown in  FIG. 5 , the number of holes  4   d  in the second internal housing  4  is smaller than the number of holes  3   d  in the first internal housing  3  and the number of holes  5   d  in the third internal housing  5 . 
     In this manner, the second internal housing  4  has a different structure from the first internal housing  3  and the third internal housing  5 . Likewise, the first internal housing  3  and the third internal housing  5  are used distinctively. Thus, it is necessary to accommodate a specified one of the internal housings  3 ,  4 , and  5  into the cavities  11 ,  12 , and  13  of the external housing  2 . Specifically, there is a reason why the internal housing  4  or the internal housing  5  should not be inserted into the cavity  11  of the external housing  2 . There is a reason why the internal housing  3  or the internal housing  5  should not be inserted into the cavity  12  of the external housing  2 . There is a reason why the internal housing  3  or the internal housing  4  should not be inserted into the cavity  13  of the external housing  2 . If the correspondence between the cavity and the internal housing is wrong, the correspondence between signal lines connected through the connector  1  is failed, and therefore the basic function of the connector  1  as a junction of signal lines is degraded. 
     Referring back to  FIG. 2 , the first cavity  11 , the second cavity  12 , and the third cavity  13  are formed in the external housing  2 . Each of the cavities  11 ,  12 , and  13  is a space surrounded by the inner wall surfaces of the external housing  2 . 
     The cavities  11 ,  12 , and  13  extend in parallel with one another. The direction in which the internal housing  3  is inserted into the cavity  11 , the direction in which the internal housing  4  is inserted into the cavity  12 , and the direction in which the internal housing  5  is inserted into the cavity  13  are parallel to one another. The cavities  11 ,  12 , and  13  extend in the direction of insertion of the plurality of internal housings  3 ,  4 , and  5 . The cavities  11 ,  12 , and  13  extend in this insertion direction. 
     As shown in  FIG. 7 , retainers  31 ,  32 , and  33  are formed on the inner wall surface of the first cavity  11 . Retainers  34 ,  35 , and  36  are formed on the inner wall surface of the second cavity  12 . Retainers  37 ,  38 , and  39  are formed on the inner wall surface of the third cavity  13 . 
     A combination of the shapes of the retainers  31 ,  32 , and  33  formed in the first cavity  11 , a combination of the shapes of the retainers  34 ,  35 , and  36  formed in the second cavity  12 , and a combination of the shapes of the retainers  37 ,  38 , and  39  formed in the third cavity  13  are different from one another. 
     Referring back to  FIG. 2 , the direction in which the cavities  11 ,  12 , and  13  extend is referred to as a Y direction, and the direction in which the cavities  11 ,  12 , and  13  are arranged next to one another is referred to as an X direction. The X direction and the Y direction are orthogonal to each other. Further, to simplify the description, it is assumed that the X direction and the Y direction are parallel, and the vertical direction orthogonal to both of the X direction and the Y direction is referred to as a Z direction. 
     Note that the X direction, the Y direction, and the Z direction are used as a coordinate system when describing the structure of the internal housings  3 ,  4 , and  5  accommodated in the cavities  11 ,  12 , and  13 , respectively. Further, as described later, the Y direction is described as the front (forward) and back (backward) direction, the X direction as the horizontal direction, and the Z direction as the vertical direction in some cases. 
     The first cavity  11  has an opening so that the first internal housing  3  can be inserted by sliding in the Y direction. Note that the side in the Y direction on which the first cavity  11  opens so that the first internal housing  3  can be inserted is the front side, and the side in the opposite direction is the back side. A wall surface is formed on the back side. 
       FIG. 6  is a view from the front side showing an example of the state where the first internal housing  3  is accommodated in the first cavity  11 , the second internal housing  4  is accommodated in the second cavity  12 , and the third internal housing  5  is accommodated in the third cavity  13 . On the other hand,  FIG. 7  is a view from the front side showing an example of the state where none of the internal housings  3 ,  4 , and  5  is accommodated in the cavities  11 ,  12 , and  13  of the external housing  2 . 
     As shown in  FIGS. 1, 2, 6 and 7 , the first cavity  11  is on the left side when viewed from the front side, the second cavity  12  is at the center when viewed from the front side, and the third cavity  13  is on the right side when viewed from the front side, they are arranged in the X direction with their positions in the Z direction aligned. In other words, the second cavity  12  is interposed between the first cavity  11  and the third cavity  13  in the X direction. 
     As shown in  FIG. 7 , the first cavity  11  includes a space between a left side wall surface  21   a  on which the left retainer  31  is formed and a right side wall surface  21   b  on which the upper right retainer  32  and the lower right retainer  33  are formed. The first cavity  11  may include the upper part of the space between the left side wall surface  21   a  and the right side wall surface  21   b.    
     The left side wall surface  21   a  and the right side wall surface  21   b  are inner side surfaces of the external housing  2 , which extend in the Y direction and are opposed to each other. Thus, the state where the first internal housing  3  is accommodated in the first cavity  11  is the state where the first internal housing  3  is inserted between the left side wall surface  21   a  and the right side wall surface  21   b  from the front side, and the first internal housing  3  is interposed and fixed between the left side wall surface  21   a  and the right side wall surface  21   b.    
     Thus, as shown in  FIG. 6 , when the first internal housing  3  is accommodated in the first cavity  11 , the most part of the first internal housing  3  is interposed between the left side wall surface  21   a  and the right side wall surface  21   b , and a part of the first internal housing  3  is disposed in the space above the space between the left side wall surface  21   a  and the right side wall surface  21   b.    
     Likewise, as shown in  FIG. 7 , the second cavity  12  has an opening so that the second internal housing  4  can be inserted from the front side. The third cavity  13  has an opening so that the third internal housing  5  can be inserted from the front side. Wall surfaces are formed on the back side. 
     The second cavity  12  is a space including the space between a left side wall surface  22   a  and a right side wall surface  22   b . The left side wall surface  22   a  and the right side wall surface  22   b  are inner side surfaces of the external housing  2 , which extend in the Y direction and are opposed to each other. The state where the second internal housing  4  is accommodated in the second cavity  12  is the state where the second internal housing  4  is inserted between the left side wall surface  22   a  and the right side wall surface  22   b  from the front side, and the second internal housing  4  is interposed and fixed between the left side wall surface  22   a  and the right side wall surface  22   b.    
     Thus, as shown in  FIG. 6 , when the second internal housing  4  is accommodated in the second cavity  12 , the most part of the second internal housing  4  is interposed between the left side wall surface  22   a  and the right side wall surface  22   b , and a part of the second internal housing  4  is disposed in the space above the space between the left side wall surface  22   a  and the right side wall surface  22   b.    
     Likewise, as shown in  FIG. 7 , the third cavity  13  is a space including the space between a left side wall surface  23   a  and a right side wall surface  23   b . The left side wall surface  23   a  and the right side wall surface  23   b  are inner side surfaces of the external housing  2 , which extend in the Y direction and are opposed to each other. The state where the third internal housing  5  is accommodated in the third cavity  13  is the state where the third internal housing  5  is inserted between the left side wall surface  23   a  and the right side wall surface  23   b  from the front side, and the third internal housing  5  is interposed and fixed between the left side wall surface  23   a  and the right side wall surface  23   b.    
     Thus, as shown in  FIG. 6 , when the third internal housing  5  is accommodated in the third cavity  13 , the most part of the third internal housing  5  is interposed between the left side wall surface  23   a  and the right side wall surface  23   b , and a part of the third internal housing  5  is disposed in the space above the space between the left side wall surface  23   a  and the right side wall surface  23   b.    
     Note that, as shown in  FIG. 7 , the wall surface on the back side of the external housing  2  has a window for pressing the internal housings  3 ,  4 , and  5  from the back side to the front side of the external housing  2  when removing the internal housings  3 ,  4 , and  5  accommodated in the external housing  2 . 
     For example, an identification part (identification mark) is placed at the end on the inserting side (the distal end in the insertion direction) of the internal housings  3 ,  4 , and  5 , so that a worker can check the identification part through the window in the wall surface on the back side of the external housing  2 . A worker can thereby identify the internal housing to be inserted into the external housing  2  from the outside of the wall surface on the back side of the external housing  2 . 
       FIGS. 8 to 10 ,  FIGS. 17 to 28 , and  FIGS. 31 to 39  are front views or cross-sectional views when viewed from the front schematically showing the external housing  2  and the internal housings  3 ,  4 , and  5 . 
     As shown in  FIG. 8 , the left retainer  31  that projects inward from the left side wall surface  21   a  and the upper right retainer  32  and the lower right retainer  33  that project inward from the right side wall surface  21   b  in the first cavity  11  are described hereinafter. 
     The left retainer  31  includes a horizontal part  31   a  projecting inward from the left side wall surface  21   a  and a vertical part  31   b  projecting vertically from the distal end of the horizontal part  31   a . The horizontal part  31   a  is one specific example of a retainer first projecting part. The vertical part  31   b  is one specific example of a retainer second projecting part. 
     Note that the retainer second projecting part is joined to the distal end of the retainer first projecting part and projects in a different direction from the projecting direction of the retainer first projecting part. The same applies to horizontal parts and vertical parts of the retainers  32  to  39 , which are described later. 
     Note that the horizontal part  31   a  and the vertical part  31   b  have shapes extending in the Y direction. In other words, the horizontal part  31   a  and the vertical part  31   b  have shapes extending along the accommodation direction when the first internal housing  3  is accommodated in the first cavity  11 . 
     The horizontal part  31   a  projects rightward. The vertical part  31   b  is formed to project upward from the distal end of the horizontal part  31   a.    
     The upper right retainer  32  includes a horizontal part  32   a  projecting inward from the right side wall surface  21   b  and a vertical part  32   b  projecting from the distal end of the horizontal part  32   a  in a different direction from the projecting direction of the horizontal part  32   a . The horizontal part  32   a  and the vertical part  32   b  have shapes extending along the accommodation direction when the first internal housing  3  is accommodated in the first cavity  11 . 
     The horizontal part  32   a  projects leftward. The vertical part  32   b  is formed to project upward from the distal end of the horizontal part  32   a.    
     The lower right retainer  33  includes a horizontal part  33   a  projecting inward from the right side wall surface  21   b . The horizontal part  33   a  has a shape extending along the accommodation direction when the first internal housing  3  is accommodated in the first cavity  11 . 
     The horizontal part  33   a  projects leftward. No vertical part is formed in the horizontal part  33   a  of the lower right retainer  33 . 
     The upper right retainer  32  is formed to be longer than the lower right retainer  33  in the Y direction. Thus, the end on the front side of the upper right retainer  32  projects more than the end on the front side of the lower right retainer  33  in the front direction. 
     The upper right retainer  32  and the lower right retainer  33  are formed parallel to each other, and the upper right retainer  32  is formed above the lower right retainer  33 . Further, it is assumed that the left retainer  31  and the lower right retainer  33  are formed at substantially the same positions in the Z direction. 
     Thus, the upper right retainer  32  is formed above the left retainer  31  and the lower right retainer  33 . 
     As shown in  FIG. 9 , the left retainer  34  that projects inward from the left side wall surface  22   a  is formed on the left side wall surface  22   a  of the second cavity  12 . The upper right retainer  35  and the lower right retainer  36  that project inward from the right side wall surface  22   b  are formed on the right side wall surface  22   b  of the second cavity  12 . 
     The left retainer  34  includes a horizontal part  34   a  projecting inward from the left side wall surface  22   a  and a vertical part  34   b  projecting from the distal end of the horizontal part  34   a  in a different direction from the projecting direction of the horizontal part  34   a . The horizontal part  34   a  and the vertical part  34   b  have shapes extending along the accommodation direction when the second internal housing  4  is accommodated in the second cavity  12 . 
     The horizontal part  34   a  projects rightward. The vertical part  34   b  is formed to project upward from the distal end of the horizontal part  34   a.    
     The upper right retainer  35  includes a horizontal part  35   a  projecting inward from the right side wall surface  22   b  and a vertical part  35   b  projecting from the distal end of the horizontal part  35   a  in a different direction from the projecting direction of the horizontal part  35   a . The horizontal part  35   a  and the vertical part  35   b  have shapes extending along the accommodation direction when the second internal housing  4  is accommodated in the second cavity  12 . 
     The horizontal part  35   a  projects leftward. The vertical part  35   b  is formed to project downward from the distal end of the horizontal part  35   a.    
     Note that, in the upper right retainer  35 , the vertical part  35   b  may be formed only partly on the front side and not formed on the back side. 
     The lower right retainer  36  includes a horizontal part  36   a  projecting inward from the right side wall surface  22   b  and a vertical part  36   b  projecting from the distal end of the horizontal part  36   a  in a different direction from the projecting direction of the horizontal part  36   a . The horizontal part  36   a  and the vertical part  36   b  have shapes extending along the accommodation direction when the second internal housing  4  is accommodated in the second cavity  12 . 
     The horizontal part  36   a  projects leftward. The vertical part  36   b  is formed to project downward from the distal end of the horizontal part  36   a.    
     The upper right retainer  35  is formed to be longer than the lower right retainer  36  in the Y direction. Thus, the end on the front side of the upper right retainer  35  projects more than the end on the front side of the lower right retainer  36  in the front direction. 
     The upper right retainer  35  and the lower right retainer  36  are formed parallel to each other, and the upper right retainer  35  is formed above the lower right retainer  36 . Further, it is assumed that the left retainer  34  and the lower right retainer  36  are formed at substantially the same positions in the Z direction. 
     Thus, the upper right retainer  35  is formed above the left retainer  34  and the lower right retainer  36 . 
     As shown in  FIG. 10 , the left retainer  37  that projects inward from the left side wall surface  23   a  is formed on the left side wall surface  23   a  of the third cavity  13 . The upper right retainer  38  that projects inward from the right side wall surface  23   b  is formed on the right side wall surface  23   b  of the third cavity  13 . 
     The left retainer  37  includes a horizontal part  37   a  projecting inward from the left side wall surface  23   a  and a vertical part  37   b  projecting from the distal end of the horizontal part  37   a  in a different direction from the projecting direction of the horizontal part  37   a . The horizontal part  37   a  and the vertical part  37   b  have shapes extending along the accommodation direction when the third internal housing  5  is accommodated in the third cavity  13 . 
     The horizontal part  37   a  projects rightward. The vertical part  37   b  is formed to project downward from the distal end of the horizontal part  37   a.    
     The upper right retainer  38  includes a horizontal part  38   a  projecting inward from the right side wall surface  23   b  and a vertical part  38   b  projecting from the distal end of the horizontal part  38   a  in a different direction from the projecting direction of the horizontal part  38   a . The horizontal part  38   a  and the vertical part  38   b  have shapes extending along the accommodation direction when the third internal housing  5  is accommodated in the third cavity  13 . 
     The horizontal part  38   a  projects leftward. The vertical part  38   b  is formed to project downward from the distal end of the horizontal part  38   a . Note that, in the upper right retainer  38 , the vertical part  38   b  may be formed only partly on the front side and not formed on the back side. 
     The lower right retainer  39  includes a horizontal part  39   a  projecting inward from the right side wall surface  23   b  and a vertical part  39   b  projecting from the distal end of the horizontal part  39   a  in a different direction from the projecting direction of the horizontal part  39   a . The horizontal part  39   a  and the vertical part  39   b  have shapes extending along the accommodation direction when the third internal housing  5  is accommodated in the third cavity  13 . 
     The horizontal part  39   a  projects leftward. The vertical part  39   b  is formed to project downward from the distal end of the horizontal part  39   a.    
     The upper right retainer  38  is formed to be longer than the lower right retainer  39  in the Y direction. Thus, the end on the front side of the upper right retainer  38  projects more than the end on the front side of the lower right retainer  39  in the front direction. 
     The upper right retainer  38  and the lower right retainer  39  are formed parallel to each other, and the upper right retainer  38  is formed above the lower right retainer  39 . Further, it is assumed that the left retainer  37  and the lower right retainer  39  are formed at substantially the same positions in the Z direction. 
     Thus, the upper right retainer  38  is formed above the left retainer  37  and the lower right retainer  39 . 
     Thus, a combination of the projecting directions of the vertical parts is as follows. 
     First, a focus is placed on a combination of the left retainers  31 ,  34 , and  37 , and the upper right retainers  32 ,  35 , and  38  in each of the cavities  11 ,  12 , and  13 . 
     In the first cavity  11 , the vertical part  31   b  of the left retainer  31  projects upward, and the vertical part  32   b  of the upper right retainer  32  projects upward, which are a combination of “up:up” Likewise, the directions of the vertical parts  34   b  and  35   b  of the retainers  34  and  35  in the second cavity  12  are a combination of “up:down”, and the directions of the vertical parts  37   b  and  38   b  of the retainers  37  and  38  in the third cavity  13  are a combination of “down:down”. 
     In this manner, a combination of the projecting directions of the vertical parts  31   b  and  32   b  of the retainers  31  and  32  in the first cavity  11 , a combination of the projecting directions of the vertical parts  34   b  and  35   b  of the retainers  34  and  35  in the second cavity  12 , and a combination of the projecting directions of the vertical parts  37   b  and  38   b  of the retainers  37  and  38  in the third cavity  13  are different from one another. 
     The same applies to the case where a focus is placed on a combination of the left retainers  31 ,  34 , and  37 , the upper right retainers  32 ,  35 , and  38 , and the lower right retainers  33 ,  36 , and  39  in each of the cavities  11 ,  12 , and  13 . 
     To be specific, as shown in  FIG. 8 , since there is no vertical part in the lower right retainer  33 , a combination of the directions of the vertical parts  31   b  and  32   b  of the retainers  31  and  32  in the first cavity  11  and a vertical part that does not exist in the lower right retainer  33  is “up:up:n/a”. As shown in  FIG. 9 , the directions of the vertical parts  34   b ,  35   b , and  36   b  of the retainers  34 ,  35 , and  36  in the second cavity  12  are a combination of “up:down:down”. As shown in  FIG. 10 , the directions of the vertical parts  37   b ,  38   b , and  39   b  of the retainers  37 ,  38 , and  39  in the third cavity  13  are a combination of “down:down:down”. Thus, the combination in the cavity  11 , the combination in the cavity  12 , and the combination in the cavity  13  are different from one another. 
     As shown in  FIGS. 8 and 10 , the horizontal part  31   a  of the left retainer  31  is slightly lower than the horizontal part  37   a  of the left retainer  37 . As shown in  FIGS. 9 and 10 , the same applies to the left retainer  34 , and the horizontal part  34   a  is slightly lower than the horizontal part  37   a  of the left retainer  37 . Specifically, as shown in  FIGS. 8 to 10 , when comprising the left retainers  31 ,  34 , and  37  of the respective cavities  11 ,  12 , and  13 , the position in the Z direction of the horizontal part of the retainer having the vertical part projecting downward is slightly upper than the position in the Z direction of the horizontal part of the retainer having the vertical part projecting upward. 
     The same applies to the upper right retainer  32 ,  35 , and  38  and the lower right retainers  36  and  39 . Although the lower right retainer  33  does not have the vertical part, the same as the case with the vertical part projecting upward applies to the lower right retainer  33 . Specifically, the position in the Z direction of the horizontal part  33   a  is slightly lower than that of the horizontal part  36   a  of the lower right retainer  36  and the horizontal part  39   a  of the lower right retainer  39 . 
     The structures of the internal housings  3 ,  4 , and  5  are described hereinafter with reference to  FIGS. 3 to 5 ,  FIGS. 11 to 16 , and  FIGS. 17 to 22 .  FIGS. 11 to 16  are views showing the left side surfaces and the right side surfaces of the internal housings  3 ,  4 , and  5 . 
       FIG. 17  is a view showing, from the front side, the X-Z cross section (the cross section A in  FIG. 11 ) on the back side in the Y direction of the first internal housing  3  and the external housing  2 , and  FIG. 18  is a view showing, from the front side, the X-Z cross section (the cross section B in  FIG. 11 ) near the front side in the Y direction of the first internal housing  3  and the external housing  2 . 
     Likewise,  FIG. 19  is a view showing, from the front side, the X-Z cross section (the cross section C in  FIG. 12 ) on the back side in the Y direction of the second internal housing  4  and the external housing  2 , and  FIG. 20  is a view showing, from the front side, the X-Z cross section (the cross section D in  FIG. 12 ) near the back side in the Y direction of the second internal housing  4  and the external housing  2 . 
     Likewise,  FIG. 21  is a view showing, from the front side, the X-Z cross section (the cross section E in  FIG. 13 ) on the back side in the Y direction of the third internal housing  5  and the external housing  2 , and  FIG. 22  is a view showing, from the front side, the X-Z cross section (the cross section F in  FIG. 13 ) near the back side in the Y direction of the third internal housing  5  and the external housing  2 . 
     As shown in  FIGS. 3 to 5 , the first internal housing  3  is formed to be long in the Y direction. Note that, as shown in  FIGS. 1 and 6 , the first internal housing  3  is inserted into the first cavity  11  along the Y direction and thereby accommodated in the first cavity  11 . 
     As shown in  FIGS. 3 to 5  and  FIGS. 11 and 12 , the first internal housing  3  has a groove part  3   a  on its left outer side surface, groove parts  3   b  and  3   c  on its right outer side surface, and two types of holes  3   d  and  3   e  that vertically penetrate the first internal housing  3 . Each of the two types of holes  3   d  and  3   e  includes a plurality of holes. 
     As shown in  FIG. 11 , the left side surface of the first internal housing  3  has the groove part  3   a  that is recessed rightward in the X direction when viewed from the front side. Stated differently, the groove part  3   a  has a shape where a part of the left side surface of the first internal housing is recessed inward in the X direction and this recess is elongated in the Y direction. 
     As shown in  FIG. 17 , the groove part  3   a  is formed at the position corresponding to the left retainer  31  when the first internal housing  3  is accommodated in the first cavity  11 . 
     As shown in  FIG. 11 , in the groove part  3   a , a projecting part  3   f  projecting downward from the upper surface is formed to extend in the Y direction. Note that the projecting part  3   f  may have slits at predetermined intervals in the Y direction. 
     As shown in  FIG. 14 , the right side surface of the first internal housing  3  has the two groove parts  3   b  and  3   c  that are recessed leftward in the X direction when viewed from the front side. Note that the groove part  3   b  is on the front side relative to the groove part  3   c . The groove part  3   b  and the groove part  3   c  are integrally formed. 
     As shown in  FIG. 18 , the groove part  3   b  is formed at the position corresponding to the upper right retainer  32  when the first internal housing  3  is accommodated in the first cavity  11 . 
     As shown in  FIG. 17 , the groove part  3   c  is formed at the position corresponding to the lower right retainer  33  when the first internal housing  3  is accommodated in the first cavity  11 . 
     As shown in  FIG. 14 , in the groove part  3   b , a projecting part  3   g  projecting downward from the upper surface is formed. In the groove part  3   c , a projecting part  3   h  projecting downward from the upper surface is formed. 
     Each of the projecting part  3   g  and the projecting part  3   h  has a shape extending in the Y direction. Note that the projecting part  3   g  and the projecting part  3   h  may have slits at predetermined intervals in the Y direction. The projecting part  3   g  and the projecting part  3   h  are formed on a straight line. 
     As shown in  FIG. 14 , the groove part  3   b  is formed only near the front side of the first internal housing  3 , and the back side of the groove part  3   b  is continuous with the groove part  3   c . Further, the vertical position in the Z direction of the bottom surface of the groove part  3   b  is upper than the bottom surface of the groove part  3   c.    
     As shown in  FIG. 17 , the projecting part  3   f  does not physically interfere with the left retainer  31  when the first internal housing  3  is accommodated into the first cavity  11 . Thus, the projecting part  3   f  does not inhibit the accommodation of the first internal housing  3  into the first cavity  11 . 
     In this case, the left retainer  31  is inserted into the groove part  3   a  in the state where a right side surface  3   i  of the projecting part  3   f  is opposed to a left side surface  31   e  of the vertical part  31   b  of the left retainer  31 . 
     Thus, when a force that brings the right side surface  3   i  of the projecting part  3   f  into contact with the left side surface  31   e  of the vertical part  31   b  is applied, the right side surface  3   i  of the projecting part  3   f  acts as a hook to receive the left side surface  31   e  of the vertical part  31   b.    
     As shown in  FIG. 14 , a plurality of projecting parts  3   g  and a plurality of projecting parts  3   h  are aligned along the Y direction. 
     As shown in  FIGS. 17 and 18 , the projecting part  3   g  and the projecting part  3   h  do not physically interfere with the upper right retainer  32  when the first internal housing  3  is accommodated into the first cavity  11 . Further, the projecting part  3   h  does not physically interfere with the lower right retainer  33 , and also the projecting part  3   g  does not physically interfere with the lower right retainer  33 . 
     Thus, the projecting part  3   g  and the projecting part  3   h  do not inhibit the accommodation of the first internal housing  3  into the first cavity  11 . 
     As shown in  FIGS. 17 and 18 , the groove part  3   a  having the projecting part  3   f  has a shape that is complementary to that of the left retainer  31  of the first cavity  11 , which is the corresponding cavity. Further, the groove part  3   b  having the projecting part  3   g  and the groove part  3   c  having the projecting part  3   h  have shapes that are complementary to those of the upper right retainer  32  and the lower right retainer  33  of the first cavity  11 . 
     Further, as shown in  FIGS. 17 and 18 , a left side surface  3   j  of the projecting part  3   g  is opposed to a right side surface  32   e  of the vertical part  32   b  of the upper right retainer  32 . When the left side surface  3   j  of the projecting part  3   g  comes into contact with the right side surface  32   e  of the vertical part  32   b , the left side surface  3   j  of the projecting part  3   g  acts as a hook to receive the right side surface  32   e  of the vertical part  32   b.    
     The same applies to the second internal housing  4  to be inserted into the second cavity  12 . 
     As shown in  FIG. 12 , in the groove part  4   a , a projecting part  4   f  projecting downward from the upper surface of the groove part  4   a  extends in the Y direction. Further, as shown in  FIG. 15 , in the groove part  4   b , a projecting part  4   g  projecting upward from the lower surface of the groove part  4   b  is formed. In the groove part  4   c , a projecting part  4   h  projecting upward from the lower surface of the groove part  4   c  is formed. 
     The projecting parts  4   f ,  4   h , and  4   g  may have slits at predetermined intervals in the Y direction. 
       FIG. 19  is a view showing a part of the X-Z cross section on the back side in the Y direction of the second internal housing  4  and the external housing  2 , and  FIG. 20  is a view showing a part of the X-Z cross section on the front side in the Y direction of the second internal housing  4  and the external housing  2 . 
     As shown in  FIG. 19 , the left retainer  34  is inserted into the groove part  4   a  in the state where a right side surface  4   i  of the projecting part  4   f  is opposed to a left side surface  34   e  of the vertical part  34   b  of the left retainer  34 . 
     Thus, when a force in the direction of bringing the right side surface  4   i  of the projecting part  4   f  into contact with the left side surface  34   e  of the vertical part  34   b  is applied, the right side surface  4   i  of the projecting part  4   f  acts as a hook to receive the left side surface  34   e  of the vertical part  34   b.    
     As shown in  FIG. 19 , the projecting part  4   f  does not physically interfere with the left retainer  34  when the second internal housing  4  is accommodated into the second cavity  12 . Thus, the projecting part  4   f  does not inhibit the accommodation of the second internal housing  4  into the second cavity  12 . 
     Further, as shown in  FIG. 15 , in the groove part  4   b , the projecting part  4   g  projecting upward from the lower surface of the groove part  4   b  is formed. In the groove part  4   c , the projecting part  4   h  projecting upward from the lower surface of the groove part  4   c  is formed. 
     As shown in  FIGS. 19 and 20 , the projecting part  4   g  does not physically interfere with the upper right retainer  35  when the second internal housing  4  is accommodated into the second cavity  12 . Further, the projecting part  4   h  does not physically interfere with the lower right retainer  36 . 
     In this manner, the groove part  4   a  having the projecting part  4   f  has a shape that is complementary to that of the left retainer  34  of the second cavity  12 , which is the corresponding cavity. Further, the groove part  4   b  having the projecting part  4   g  and the groove part  4   c  having the projecting part  4   h  have shapes that are complementary to those of the upper right retainer  35  and the lower right retainer  36  of the second cavity  12 . 
     Note that, as shown in  FIGS. 19 and 20 , a left side surface  4   j  of the projecting part  4   g  is opposed to a right side surface  35   e  of the vertical part  35   b  of the upper right retainer  35 . When the left side surface  4   j  of the projecting part  4   g  comes into contact with the right side surface  35   e  of the vertical part  35   b , the left side surface  4   j  of the projecting part  4   g  acts as a hook to receive the right side surface  35   e  of the vertical part  35   b . Likewise, a left side surface  4   k  of the projecting part  4   h  is opposed to a right side surface  36   e  of the vertical part  36   b  of the lower right retainer  36 . When the left side surface  4   k  of the projecting part  4   h  comes into contact with the right side surface  36   e  of the vertical part  36   b , the left side surface  4   k  of the projecting part  4   h  acts as a hook to receive the right side surface  36   e  of the vertical part  36   b.    
     The same applies to the third internal housing  5  to be inserted into the third cavity  13 . 
     As shown in  FIG. 13 , in the groove part  5   a , a projecting part  5   f  that projects upward from the lower surface of the groove part  5   a  extends in the Y direction. Further, as shown in  FIG. 16 , in the groove part  5   b , a projecting part  5   g  that projects upward from the lower surface of the groove part  5   b  is formed. In the groove part  5   c , a projecting part  5   h  projecting upward from the lower surface of the groove part  5   c  is formed. 
     The projecting parts  5   f ,  5   h , and  5   g  may have slits at predetermined intervals in the Y direction. 
       FIG. 21  is a view showing a part of the X-Z cross section on the back side in the Y direction of the third internal housing  5  and the external housing  2 , and  FIG. 22  is a view showing a part of the X-Z cross section near the front side in the Y direction of the third internal housing  5  and the external housing  2 . 
     As shown in  FIG. 21 , the horizontal part  37   a  is disposed above the projecting part  5   f , and a right side surface  5   i  of the projecting part  5   f  is opposed to a left side surface  37   e  of the vertical part  37   b  of the left retainer  37 . Thus, when a force in the direction of bringing the right side surface  5   i  of the projecting part  5   f  into contact with the left side surface  37   e  of the vertical part  37   b  is applied, the right side surface  5   i  of the projecting part  5   f  acts as a hook to receive the left side surface  37   e  of the vertical part  37   b.    
     As shown in  FIG. 21 , the projecting part  5   f  does not physically interfere with the left retainer  37  when the third internal housing  5  is accommodated into the third cavity  13 . Thus, the projecting part  5   f  does not inhibit the accommodation of the third internal housing  5  into the third cavity  13 . 
     Further, as shown in  FIG. 16 , in the groove part  5   b , the projecting part  5   g  projecting upward from the lower surface of the groove part  5   b  is formed. As shown in  FIG. 16 , in the groove part  5   c , the projecting part  5   h  projecting upward from the lower surface of the groove part  5   c  is formed. 
     As shown in  FIGS. 21 and 22 , the projecting part  5   g  does not physically interfere with the upper right retainer  38  when the third internal housing  5  is accommodated into the third cavity  13 . Further, the projecting part  5   h  does not physically interfere with the lower right retainer  39 . 
     In this manner, the groove part  5   a  having the projecting part  5   f  has a shape that is complementary to that of the left retainer  37  of the third cavity  13 , which is the corresponding cavity. Further, the groove part  5   b  having the projecting part  5   g  and the groove part  5   c  having the projecting part  5   h  have shapes that are complementary to those of the upper right retainer  38  and the lower right retainer  39  of the third cavity  13 . 
     Note that, as shown in  FIGS. 21 and 22 , a left side surface  5   j  of the projecting part  5   g  is opposed to a right side surface  38   e  of the vertical part  38   b  of the upper right retainer  38 . When the left side surface  5   j  of the projecting part  5   g  comes into contact with the right side surface  38   e  of the vertical part  38   b , the left side surface  5   j  of the projecting part  5   g  acts as a hook to receive the right side surface  38   e  of the vertical part  38   b . Likewise, a left side surface  5   k  of the projecting part  5   h  is opposed to a right side surface  39   e  of the vertical part  39   b  of the lower right retainer  39 . When the left side surface  5   k  of the projecting part  5   h  comes into contact with the right side surface  39   e  of the vertical part  39   b , the left side surface  5   k  of the projecting part  5   h  acts as a hook to receive the right side surface  39   e  of the vertical part  39   b.    
     The case where the internal housing  3 ,  4 , or  5  is wrongly inserted into a cavity different from the target cavity is described hereinafter with reference to  FIGS. 23 to 28 .  FIGS. 23 to 28  are views showing the cross section of the external housing  2  on the back side and the cross section of each of the internal housings  3 ,  4 , and  5  in an overlapping manner. 
     As shown in  FIG. 23 , when the first internal housing  3  is about to be inserted into the second cavity  12 , the projecting part  3   h  in the groove part  3   c  physically interferes with the horizontal part  35   a  of the upper right retainer  35 . This prevents wrong insertion of the first internal housing  3  into the second cavity  12 . 
     As shown in  FIG. 24 , when the first internal housing  3  is about to be inserted into the third cavity  13 , the projecting part  3   f  physically interferes with the horizontal part  37   a  of the left retainer  37 . At the same time, the projecting part  3   h  physically interferes with the horizontal part  38   a  of the upper right retainer  38 . This prevents wrong insertion of the first internal housing  3  into the third cavity  13 . 
     As shown in  FIG. 25 , when the second internal housing  4  is about to be inserted into the first cavity  11 , the projecting part  4   h  in the groove part  4   c  physically interferes with the horizontal part  33   a  of the lower right retainer  33 . 
     In this case, since the projecting part  4   g  is on the front side relative to the projecting part  4   h , the projecting part  4   h  physically interferes with the horizontal part  33   a  of the lower right retainer  33  before the projecting part  4   g  physically interferes with the horizontal part  32   a  of the upper right retainer  32 . This prevents wrong insertion of the second internal housing  4  into the first cavity  11 . 
     As shown in  FIG. 26 , when the second internal housing  4  is about to be inserted into the third cavity  13 , the projecting part  4   f  in the groove part  4   a  physically interferes with the horizontal part  37   a  of the left retainer  37 . This prevents wrong insertion of the second internal housing  4  into the third cavity  13 . 
     As shown in  FIG. 27 , when the third internal housing  5  is about to be inserted into the first cavity  11 , the projecting part  5   h  in the groove part  5   c  physically interferes with the horizontal part  33   a  of the lower right retainer  33 . In this case, since the projecting part  5   g  is on the front side relative to the projecting part  5   h , the projecting part  5   h  physically interferes with the horizontal part  33   a  of the lower right retainer  33  before the projecting part  5   g  physically interferes with the horizontal part  32   a  of the upper right retainer  32 . This prevents wrong insertion of the third internal housing  5  into the first cavity  11 . As shown in  FIG. 28 , when the third internal housing  5  is about to be inserted into the second cavity  12 , the projecting part  5   f  in the groove part  5   a  physically interferes with the horizontal part  34   a  of the left retainer  34 . This prevents wrong insertion of the third internal housing  5  into the second cavity  12 . 
     Thus, the first internal housing  3  is restricted so that it can be inserted only into the first cavity  11  and cannot be inserted into the other cavities  12  and  13  by a combination of the shapes of the groove parts  3   a ,  3   b , and  3   c  having the projecting parts  3   f ,  3   g  and  3   h  and the shapes of the retainers  31 ,  32 , and  33  of the first cavity  11 . 
     Likewise, the second internal housing  4  is restricted so that it can be inserted only into the second cavity  12  and cannot be inserted into the other cavities  11  and  13  by a combination of the shapes of the groove parts  4   a ,  4   b , and  4   c  having the projecting parts  4   f ,  4   g , and  4   h  and the shapes of the retainers  34 ,  35 , and  36  of the second cavity  12 . 
     Likewise, the third internal housing  5  is restricted so that it can be inserted only into the third cavity  13  and cannot be inserted into the other cavities  11  and  12  by a combination of the shapes of the groove parts  5   a ,  5   b , and  5   c  having the projecting parts  5   f ,  5   g , and  5   h  and the shapes of the retainers  37 ,  38 , and  39  of the third cavity  13 . 
     In this manner, insertion into a cavity is allowed only when the shapes of all groove parts in the internal housing and the shapes of all projecting parts in the external housing  2  completely match. 
     Stated differently, an objective of preventing wrong insertion of the internal housing into the external housing  2  is achieved when the shapes of some groove parts and the shapes of some projecting parts match but not all of the shapes match and there is a mismatch part. 
     Note that an objective of preventing wrong insertion into the external housing  2  is achieved as a matter of course when the shapes of all groove parts and the shapes of all projecting parts do not match. 
     A plurality of holes that vertically penetrate the first internal housing  3  and terminals to be inserted into the holes are described hereinafter with reference to  FIGS. 3 to 5  and  FIGS. 29 and 30 . 
     As shown in  FIGS. 3 to 5 , the first internal housing  3  has two types of holes that vertically penetrate the first internal housing  3  in the Z direction. The two types of holes are first holes  3   d  and second holes  3   e.    
     The first holes  3   d  are formed on the back side in the Y direction relative to the second holes  3   e . Typically, as shown in  FIGS. 3 to 5 , the first holes  3   d  are in two rows in the X direction, and a plurality of first holes  3   d  are aligned in the Y direction. 
     In each of the first holes  3   d , a first terminal  42  that is crimped onto the distal end of the first wire  41  is inserted from above. 
       FIG. 29  is an example of the first wire  41  and the first terminal  42  that is crimped onto the first wire  41 . Typically, the first wire  41  is a wire that is used for signal transmission. In this example, each of the first wire  41  and the first terminal  42  has a shape extending in the Z direction. 
     The first terminal  42  includes a first latching part  42   a  that is formed to project from its side surface in a direction orthogonal to the direction along which the terminal extends. 
       FIG. 31  is a view showing the state where the first internal housing  3  into which the first terminal  42  is inserted is accommodated in the external housing  2 . 
     The first latching part  42   a  projects leftward from the first terminal  42  when viewed from the front in the case where the first terminal  42  is inserted into the left row of the first hole  3   d  consisting of two rows in the first internal housing  3 . On the other hand, the first latching part  42   a  projects rightward from the first terminal  42  when viewed from the front in the case where the first terminal  42  is inserted into the right row of the first hole  3   d  consisting of two rows in the first internal housing  3 . 
     As shown in  FIG. 31 , when the first internal housing  3  is accommodated in the first cavity  11 , the position of the first latching part  42   a  when the first terminal  42  is inserted into the first hole  3   d  is below the left retainer  31  and the lower right retainer  33 . 
     The plurality of first terminals  42  are aligned along the Y direction in each of the right row and the left row. Thus, the left retainer  31  or the lower right retainer  33  is inserted above the first latching part  42   a  in each of the first terminals  42  in the same manner. 
       FIG. 32  is a view showing an example of the positional relationship between the first terminal  42  and the external housing  2  when the first internal housing  3  is accommodated in the first cavity  11 , where the illustration of the first internal housing is omitted for easier understanding. 
     As shown in  FIG. 32 , in the first terminal  42  disposed in the left row in the first internal housing  3 , an upper surface  42   b  of the first latching part  42   a  is opposed to an under surface  31   c  of the horizontal part  31   a  near the distal end of the horizontal part  31   a  of the retainer  31  of the external housing  2 . 
     For example, when a force of pulling up the first terminal  42  is applied to the first terminal  42  that is inserted into the first hole  3   d  in the left row, the upper surface  42   b  of the first latching part  42   a  comes into contact with the under surface  31   c  of the left retainer  31 . The first terminal  42  is thereby secondarily locked by the external housing  2 , which prevents the first terminal  42  from being pulled out of the first hole  3   d.    
     Likewise, when a force of pulling up the first terminal  42  is applied to the first terminal  42  that is inserted into the first hole  3   d  in the right row, the upper surface  42   b  of the first latching part  42   a  comes into contact with an under surface  33   c  of the lower right retainer  33  that extends inward of the first cavity  11 . The first terminal  42  is thereby secondarily locked by the external housing  2 , which prevents the first terminal  42  from being pulled out of the first hole  3   d.    
     Note that, the first terminal  42  has a recess that is recessed in the X direction above the first latching part  42   a , which is the upper part of the first latching part  42   a . Specifically, in the first terminal  42 , the left retainer  31 , the upper right retainer  32 , and the lower right retainer  33  are placed in this recess. The recess is formed by crimping the first wire  41  to the first terminal  42 . 
     The same applies to the second internal housing  4 . 
     In the second internal housing  4 , as shown in  FIG. 33 , the upper surface  42   b  of the first latching part  42   a  in the first terminal  42  is vertically opposed to an under surface  36   d  of the vertical part  36   b  in the lower right retainer  36  that extends inward of the second cavity  12 . 
     The first terminal  42  is thereby secondarily locked by the external housing  2 , which prevents the first terminal  42  from being pulled out of the first hole  4   d.    
     The same applies to the third internal housing  5 . 
     In the third internal housing  5 , as shown in  FIG. 34 , the upper surface  42   b  of the first latching part  42   a  in the first terminal  42  is vertically opposed to an under surface  37   d  of the vertical part  37   b  in the left retainer  37 . 
     Further, in the first terminal  42  that is inserted into the first hole  3   d  in the right row, the upper surface  42   b  of the first latching part  42   a  is vertically opposed to an under surface  39   d  of the vertical part  39   b  in the lower right retainer  39 . 
     The first terminal  42  is thereby secondarily locked by the external housing  2 , which prevents the first terminal  42  from being pulled out of a first hole  5   d.    
     A second wire  43  that is inserted into the second hole  3   e  is described hereinafter with reference to  FIGS. 3 to 5  and  FIG. 30 . 
     As shown in  FIGS. 3 to 5 , the second holes  3   e  are on the front side in the Y direction relative to the first holes  3   d . The second holes  3   e  are aligned along the Y direction. 
     In each of the second holes  3   e , a second terminal  44  that is crimped onto the distal end of a second wire  43  is inserted from above. 
       FIG. 30  is an example of the second terminal  44  that is crimped onto the second wire  43 . Typically, the second wire  43  is a wire that is used for power supply.  FIGS. 3 and 4  show the state where the two second wires  43  are aligned in the Y direction. In this example, each of the two second wires  43  and the second terminal  44  has a shape extending in the Z direction. 
     The second terminal  44  includes a second latching part  44   a  that is formed to project from a part of the side surface of the second terminal  44  in a direction orthogonal to the direction along which the terminal extends. When the second terminal  44  is inserted into the second hole  3   e , the second latching part  44   a  is on the right side of the second terminal  44 . 
     In the case where the first internal housing  3  is accommodated in the first cavity  11 , the position of the second latching part  44   a  when the second terminal  44  is inserted into the second hole  3   e  is below the upper right retainer  32 . 
     The plurality of second terminals  44  are aligned along the Y direction. Thus, the upper right retainer  32  is inserted above the second latching part  44   a  of any of the second terminals  44  in the same manner. 
       FIG. 35  is an X-Z cross-sectional view showing the second terminal  44  that is inserted into the first internal housing  3 . Although  FIG. 35  shows the state where the first internal housing  3  is accommodated in the external housing  2 , the illustration of the first internal housing  3  is omitted for better understanding, and only the right side wall surface  21   b  is shown in the external housing  2 . 
     As shown in  FIG. 35 , in the first internal housing  3 , an upper surface  44   b  of the second latching part  44   a  in the second terminals  44  is opposed to an under surface  32   c  of the horizontal part  32   a  near the distal end of the horizontal part  32   a  of the upper right retainer  32 . 
     For example, when a force of pulling up the second terminal  44  is applied to the second terminal  44 , the upper surface  44   b  of the second latching part  44   a  comes into contact with the under surface  32   c  of the upper right retainer  32 . The second terminal  44  is thereby secondarily locked by the external housing  2 , which prevents the second terminal  44  from being pulled out of the second hole  3   e.    
     Typically, the second wire  43 , which is a wire for power transmission, has a larger diameter than the first wire  41 , which is a wire for signal transmission. Thus, the second terminal  44  is larger than the first terminal  42 . 
     Thus, the position at which the first latching part  42   a  is formed in the first terminal  42  is different from the position at which the second latching part  44   a  is formed in the second terminal  44 . To be more specific, the distance from the distal end of the second terminal to the part where the second latching part  44   a  is formed is longer than the distance from the distal end of the first terminal to the part where the first latching part  42   a  is formed. 
     This allows adjustment so that the second terminal  44  with the second latching part  44   a  comes into contact with the upper right retainer  32  and is thereby secondarily locked when the first terminal  42  with the first latching part  42   a  comes into contact with the left retainer  31  and the lower right retainer  33  and is thereby secondarily locked. 
     Although the first internal housing  3  is described above as an example, the same applies to the second internal housing  4 . 
     In the second internal housing  4 , as shown in  FIG. 36 , the upper surface  44   b  of the second latching part  44   a  in the second terminal  44  comes into contact with an under surface  35   d  of the vertical part  35   b  in the upper right retainer  35  that extends inward of the second cavity  12 . 
     The second terminal  44  is thereby secondarily locked by the external housing  2 , which prevents the second terminal  44  from being pulled out of the second hole  4   e.    
     The same applies to the third internal housing  5 . 
     In the third internal housing  5 , as shown in  FIG. 37 , the upper surface  44   b  of the second latching part  44   a  in the second terminal  44  comes into contact with an under surface  38   d  of the vertical part  38   b  in the lower right retainer  39  that extends inward of the third cavity  13 . 
     The second terminal  44  is thereby secondarily locked by the external housing  2 , which prevents the second terminal  44  from being pulled out of the second hole  5   e.    
       FIG. 38  shows an example of the case where each of the first terminals  42  in the left row and the right row is about to be inserted into the external housing  2  in the state where it is not completely inserted into the first internal housing  3 . The “state where the first terminal  42  is not completely inserted into the first internal housing  3 ” indicates the state where the first terminal  42  is inserted into the corresponding hole of the first internal housing  3  but not inserted to the normal position. 
     In this case, the first latching part  42   a  of the first terminal  42  disposed in the left row projects into the groove part  3   a . Thus, when the first internal housing  3  is about to be inserted into the external housing  2 , the first latching part  42   a  physically interferes with the left retainer  31 . 
     Likewise, the first latching part  42   a  of the first terminal  42  disposed in the right row projects into the groove part  3   c . Thus, when the first internal housing  3  is about to be inserted into the external housing  2 , the first latching part  42   a  physically interferes with the lower right retainer  33 . 
     This allows detecting that the first terminal  42  is not completely inserted. 
     Incomplete insertion of the first terminal is detectable in the same manner in the second internal housing  4  and the third internal housing  5 . 
     For the second terminal  44  also, incomplete insertion is detectable depending on whether there is physical interference with the upper right retainer  32 ,  35 , or  38 . 
     The retainers  31 ,  32 , and  34  to  39  in the external housing  2  include the vertical parts  31   b ,  32   b ,  34   b  to  39   b  at the distal ends of the horizontal parts  31   a ,  32   a ,  34   a  to  39   a , respectively, so that they are shaped like a hook when viewed from the front. The effect of having the hook shape is described hereinafter. 
     An example of the case where the retainer does not have a hook shape is described first.  FIG. 39  is a view based on the assumption that the left retainer  31  does not have the vertical part  31   b  and thus not have a hook shape. 
     When the first terminal  42  is not completely inserted into the first internal housing  3 , and further the first internal housing  3  is about to be forcibly inserted into the first cavity  11 , the left side wall surface  21   a  is warped leftward because the inner wall of the external housing  2  is thin. This can cause the first internal housing  3  to push past the retainer  31  and become inserted into the external housing  2 . 
     An example of the case where the retainer has a hook shape is described next. As shown in  FIG. 40 , the left retainer  31  has the vertical part  31   b , and when a force of warping the external housing  2  is applied, the vertical part  31   b  of the left retainer  31  and the projecting part  3   f  of the first internal housing  3  come into contact with each other. The inner wall surface of the first cavity  11  and the outer wall surface of the first internal housing  3  are thereby restrained by each other, which prevents the occurrence of warp deformation of the external housing  2 . 
     Further, in this case, since warp deformation does not occur in the external housing  2 , even when the first internal housing  3  in which the first terminal  42  is not completely inserted is about to be forcibly inserted into the first cavity  11 , the first terminal  42  comes into contact with the left retainer  31  in the insertion direction of the first internal housing  3 , which stops the insertion of the first internal housing  3 . This prevents the first internal housing  3  in which the first terminal  42  is not completely inserted from being inserted into the external housing  2 . 
     Although the case where the left retainer  31  of the first internal housing  3  has a hook shape is described above, the same applies to the other internal housings  4  and  5 , and the other retainers in a hook shape. Further, the case where a force of warping the external housing  2  is generated due to incomplete insertion of the first terminal  42  is described above, the same applies to the case where a force of warping the external housing  2  is generated by different reasons. 
     As described above, even when the external housing  2  is thin and a force of deforming the external housing  2  is applied, the vertical parts  31   b ,  32   b ,  34   b  to  39   b  act as a hook, which prevents the deformation of the external housing  2 . Further, this prevents the internal housings  3  to  5  into which the terminal  42  or  44  is not completely inserted from being inserted into the external housing  2 . 
     In this structure, when inserting a plurality of internal housings into a plurality of cavities, a restriction is placed so that each internal housing is not inserted into a cavity different from the corresponding cavity. Further, since a new structure is not added to place this restriction, this contributes to size reduction of a connector. 
     Further, in this structure, the function of restraining the inner wall surface of the cavity and the outer wall surface of the internal housing with each other is achieved with a retainer of a simple shape. 
     Further, even if a plurality of wires using a different types of terminals are inserted into one internal housing when the internal housings  3 ,  4  and  5  are accommodated in the external housing  2 , the retainer projecting from the inner wall surface that forms the cavity of the external housing  2  and the latching part of each terminal come into contact with each other, so that secondary locking of each terminal is achieved. 
     Further, in the connector  1 , when any of the terminals  42  and  44  inserted into the internal housing  3 ,  4  or  5  is not completely inserted, the latching part of the terminal physically interferes with the retainer when inserting the internal housing into the external housing  2 , so that the incomplete insertion state of the terminal is detected. 
     Furthermore, when any of the terminals inserted into each internal housing is not sufficiently inserted, the retainer physically interferes with this terminal in the housing insertion direction without secondarily locking the terminal. As a result, the retainer runs on this terminal, and the inner wall surface of the cavity in which the retainer is formed is deformed in a direction away from the outer wall surface of the internal housing, which can break the external housing. In the above-described structure, since the retainer has a bent shape and the corresponding groove part has a shape that is complementary to the shape of the retainer, the inner wall surface of the cavity and the outer wall surface of the internal housing are restrained by each other, which prevents the breakage of the external housing. 
     The above-described embodiment has the following first and second features. 
     (First Feature) 
     The inner wall surface of each of the cavities includes a first inner wall surface and a second inner wall surface opposed to each other. The first inner wall surfaces of the plurality of cavities face in the same direction. The plurality of cavities include a first cavity and a second cavity. The retainer of the first cavity has an L shape that projects from the first inner wall surface toward the second inner wall surface and further projects upward. The retainer of the second cavity has an L shape that projects from the first inner wall surface toward the second inner wall surface and further projects downward. In this structure, the retainers having different shapes from one another are achieved in a simple structure. The above feature is obviously shown particularly in  FIGS. 9 and 10  in the above-described embodiment. 
     Specifically, as shown in  FIG. 9 , the inner wall surface of each cavity ( 12 ,  13 ) includes the first inner wall surface and the second inner wall surface that are opposed to each other. To be specific, the inner wall surface of the cavity  12  includes the left side wall surface  22   a  (first inner wall surface) and the right side wall surface  22   b  (second inner wall surface) that are opposed to each other. As shown in  FIG. 10 , the inner wall surface of the cavity  13  includes the left side wall surface  23   a  (first inner wall surface) and the right side wall surface  23   b  (second inner wall surface) that are opposed to each other. 
     As shown in  FIGS. 9 and 10 , the inner wall surfaces of the plurality of cavities ( 12  and  13 ) face in the same direction. To be specific, both of the left side wall surface  22   a  (first inner wall surface) of the cavity  12  shown in  FIG. 9  and the left side wall surface  23   a  (first inner wall surface) of the cavity  13  shown in  FIG. 10  face in the same direction (rightward). 
     The plurality of cavities ( 12  and  13 ) include the first cavity and the second cavity. To be specific, the plurality of cavities ( 12  and  13 ) include the cavity  12  (first cavity) and the cavity  13  (second cavity). 
     The retainer of the first cavity has an L shape that projects from the first inner wall surface toward the second inner wall surface and further projects upward. To be specific, as shown in  FIG. 9 , the left retainer  34  (retainer) of the cavity  12  has an L shape that projects from the left side wall surface  22   a  (first inner wall surface) toward the right side wall surface  22   b  (second inner wall surface) and further projects upward. 
     The retainer of the second cavity has an L shape that projects from the first inner wall surface toward the second inner wall surface and further projects downward. To be specific, as shown in  FIG. 10 , the left retainer  37  (retainer) of the cavity  13  has an L shape that projects from the left side wall surface  23   a  (first inner wall surface) toward the right side wall surface  23   b  (second inner wall surface) and further projects downward. 
     (Second Feature) 
     The inner wall surface of each of the cavities includes a first inner wall surface and a second inner wall surface opposed to each other. The first inner wall surfaces of the plurality of cavities face in the same direction. In each of the cavities, a first retainer disposed on the first inner wall surface and a second retainer disposed on the second inner wall surface are formed as the retainer. A shape pattern of each of the cavities is any one of following four shape patterns. There is no duplication of the shape patterns among the plurality of cavities.
         A first shape pattern where the first retainer has an L shape that projects from the first inner wall surface toward the second inner wall surface and further projects upward, and the second retainer has an L shape that projects from the second inner wall surface toward the first inner wall surface and further projects upward   A second shape pattern where the first retainer has an L shape that projects from the first inner wall surface toward the second inner wall surface and further projects upward, and the second retainer has an L shape that projects from the second inner wall surface toward the first inner wall surface and further projects downward   A third shape pattern where the first retainer has an L shape that projects from the first inner wall surface toward the second inner wall surface and further projects downward, and the second retainer has an L shape that projects from the second inner wall surface toward the first inner wall surface and further projects upward   A fourth shape pattern where the first retainer has an L shape that projects from the first inner wall surface toward the second inner wall surface and further projects downward, and the second retainer has an L shape that projects from the second inner wall surface toward the first inner wall surface and further projects downward       

     As described above, since there are four possible shape patterns that are different from one another, even when the connector  1  includes four cavities at the maximum, this structure prevents each internal housing from being inserted into a cavity different from a corresponding cavity when inserting a plurality of internal housings into a plurality of cavities formed in an external housing. The above feature is obviously shown particularly in  FIGS. 9 and 10  in the above-described embodiment. 
     Specifically, as shown in  FIG. 9 , the inner wall surface of each cavity ( 12 ,  13 ) includes the first inner wall surface and the second inner wall surface that are opposed to each other. To be specific, the inner wall surface of the cavity  12  includes the left side wall surface  22   a  (first inner wall surface) and the right side wall surface  22   b  (second inner wall surface) that are opposed to each other. As shown in  FIG. 10 , the inner wall surface of the cavity  13  includes the left side wall surface  23   a  (first inner wall surface) and the right side wall surface  23   b  (second inner wall surface) that are opposed to each other. 
     As shown in  FIGS. 9 and 10 , the inner wall surfaces of the plurality of cavities ( 12  and  13 ) face in the same direction. To be specific, both of the left side wall surface  22   a  (first inner wall surface) of the cavity  12  shown in  FIG. 9  and the left side wall surface  23   a  (first inner wall surface) of the cavity  13  shown in  FIG. 10  face in the same direction (rightward). 
     In each of the cavities, the first retainer disposed on the first inner wall surface and the second retainer disposed on the second inner wall surface are formed as the retainer. To be specific, as shown in  FIG. 9 , in the cavity  12 , the left retainer  34  (first retainer) disposed on the left side wall surface  22   a  (first inner wall surface) and the lower right retainer  36  (second retainer) disposed on the right side wall surface  22   b  (second inner wall surface) are formed as the retainer. Likewise, as shown in  FIG. 10 , in the cavity  13 , the left retainer  37  (first retainer) disposed on the left side wall surface  23   a  (first inner wall surface) and the lower right retainer  39  (second retainer) disposed on the right side wall surface  23   b  (second inner wall surface) are formed as the retainer. 
     A shape pattern of each of the cavities is any one of following four shape patterns. There is no duplication of the shape patterns among the plurality of cavities ( 12  and  13 ). 
     The four shape patterns include a first shape pattern to a fourth shape pattern. 
     The first shape pattern is a pattern where the first retainer (left-side retainer) has a shape of L bending upward, and the second retainer (right-side retainer) has a shape of L bending upward. 
     The second shape pattern is a pattern where the first retainer (left-side retainer) has a shape of L bending upward, and the second retainer (right-side retainer) has a shape of L bending downward. The shape pattern of the cavity  12  shown in  FIG. 9  corresponds to the second shape pattern. 
     The third shape pattern is a pattern where the first retainer (left-side retainer) has a shape of L bending downward, and the second retainer (right-side retainer) has a shape of L bending upward. 
     The fourth shape pattern is a pattern where the first retainer (left-side retainer) has a shape of L bending downward, and the second retainer (right-side retainer) has a shape of L bending downward. The shape pattern of the cavity  13  shown in  FIG. 10  corresponds to the fourth shape pattern. 
     The first retainer (left-side retainer) having a shape of L bending upward has an L shape that projects from the first inner wall surface toward the second inner wall surface and further projects upward. To be specific, as shown in  FIG. 9 , the left retainer  34  (first retainer) disposed on the left side wall surface  22   a  (first inner wall surface) has an L shape that includes the horizontal part  34   a  that projects from the left side wall surface  22   a  (first inner wall surface) toward the right side wall surface  22   b  (second inner wall surface) and the vertical part  34   b  that projects upward from the horizontal part  34   a.    
     The first retainer (left-side retainer) having a shape of L bending downward means the first retainer having an L shape that projects from the first inner wall surface toward the second inner wall surface and further projects downward. To be specific, as shown in  FIG. 10 , the left retainer  37  (first retainer) disposed on the left side wall surface  23   a  (first inner wall surface) has an L shape that includes the horizontal part  37   a  that projects from the left side wall surface  23   a  (first inner wall surface) toward the right side wall surface  23   b  (second inner wall surface) and the vertical part  37   b  that projects downward from the horizontal part  37   a.    
     The second retainer (right-side retainer) having a shape of L bending upward means the second retainer having an L shape that projects from the second inner wall surface toward the first inner wall surface and further projects upward. 
     The second retainer (right-side retainer) having a shape of L bending downward means the second retainer having an L shape that projects from the second inner wall surface toward the first inner wall surface and further projects downward. To be specific, as shown in  FIG. 10 , the lower right retainer  39  (second retainer) disposed on the right side wall surface  23   b  (second inner wall surface) has an L shape that includes the horizontal part  39   a  that projects from the right side wall surface  23   b  (second inner wall surface) toward the left side wall surface  23   a  (first inner wall surface) and the vertical part  39   b  that projects downward from the horizontal part  39   a.    
     Note that the present disclosure is not limited to the above-described embodiments and can be modified as appropriate without departing from the spirit and scope of the present disclosure. 
     As shown in  FIG. 1 , the case where the three internal housings  3 ,  4 , and  5  are accommodated in the external housing  2  is described above. However, the present disclosure is not limited to thereto, and four or more internal housings may be accommodated. Further, in the external housing  2 , a pattern of combination of projecting parts (shape patterns) increases by increasing the number of projecting parts formed in a plurality of cavities. 
     In this specification, “complementary shape” does not mean that no gap is left between an internal housing and an inner wall surface of a cavity when the internal housing is inserted into the cavity. A certain gap is left between the internal housing and the inner wall surface of the cavity when the internal housing is inserted into the cavity so that the internal housing is easily inserted into the cavity. This gap also functions to absorb dimensional manufacturing errors in the internal housing and the external housing. 
     From the disclosure thus described, it will be obvious that the embodiments of the disclosure may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.