Patent Publication Number: US-10333246-B2

Title: Waterproof structure of connector

Description:
TECHNICAL FIELD 
     The present invention relates to a waterproof structure of a connector. 
     BACKGROUND ART 
     In the related art, a waterproof connector for connecting electric wires has been mounted on an automobile or the like. For example, a waterproof connector has been known which includes a female connector in which a tubular inner housing formed with a cavity for accommodating a female terminal and a tubular outer housing surrounding the inner housing are integrally formed, and a female connector having a tubular male housing in which a cavity for accommodating a male terminal is formed, and the a waterproof connector is formed by fitting both connectors. 
     In this type of waterproof connector, an annular rubber packing is mounted on the outer circumferential surface of the inner housing of the female connector. When both connectors are fitted together, the male housing is inserted into a gap between the inner housing and the outer housing of the female connector. The packing is brought into close contact with an outer circumferential surface of the inner housing and an inner circumferential surface of the male housing, respectively, thereby preventing water from entering the gap between the cavities. 
     However, this type of waterproof structure requires a space for mounting the packing inside the female connector. Therefore, the outer diameter size of the waterproof connector increases. Also, the male housing is inserted into the female housing, while pressing the packing. Therefore, the load upon insertion of the male housing is increased. Thus, as a waterproof structure which does not use packing, for example, a structure is known in which a disc-shaped elastic plate is provided on the inner surface on the back side of the female housing, and when both connectors are fitted together, the housing leading end in the fitting direction of the male housing inserted into the female housing is brought into contact with the sealing plate to prevent water from entering (for example, see Patent Literature 1). 
     PRIOR ART DOCUMENTS 
     Patent Literature 
     [Patent Literature 1]: JP-A-2013-229168 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     However, in the waterproof structure disclosed in Patent Literature 1, when the male housing is brought into contact with the sealing plate, an excessive load may be generated on at least one of both housings. For example, when the axial length of one housing is formed at the upper limit of the tolerance or when the male housing is pressed against the seal plate in a state in which foreign matter or the like is caught in the gap between the male housing and the seal plate, the male housing exceeds the elastic limit and plastically deforms, and the waterproof performance may be deteriorated. 
     The present invention has been made in view of such a problem, and an object thereof is to provide a waterproof structure of a connector which can prevent deterioration of waterproof performance due to plastic deformation of a connector. 
     Solution to Problem 
     In order to solve the above problem, a waterproof structure of a connector of the present invention is a waterproof structure of a connector in which cavities respectively accommodating terminals are formed respectively in a pair of housings configured to be fitted to each other. In each of the pair of housings, an annular member surrounding an opening of the cavity is formed to protrude in a fitting direction. One of the annular members has a plurality of corner parts in which an outer circumferential surface is inclined so as to spread outward in a radial direction from a leading end to inward. The outer circumferential surface presses an inner circumferential surface of the other annular member in fitting, and in a cross section orthogonal to the fitting direction. The plurality of corner parts are positioned to be symmetrical with each other with respect to a central axis of the annular member. A curvature of the outer circumferential surface of the plurality of corner parts is larger than a curvature of the outer circumferential surface of other portions. An inclination angle of the outer circumferential surface of the corner part with respect to the fitting direction is larger than an inclination angle of the outer circumferential surface of other portions with respect to the fitting direction. 
     According to this configuration, the outer circumferential surface of one annular member is formed in a shape that presses the inner circumferential surface of the other annular member. Therefore, when the pair of housings is fitted to each other, the inner circumferential surface of the other annular member is elastically deformed by being pressed by the outer circumferential surface of the one annular member, and the outer circumference of the one tubular member is pushed by the restoring force of this elastic deformation. In this manner, since the annular members are pressed against each other over the entire circumference within the elastic limit, it is possible to prevent water from entering between the annular members. In this way, it is possible to prevent deterioration of the waterproof performance of the connector due to plastic deformation. Further, by bringing the annular members into direct contact with each other, there is no need for a space for providing the rubber packing inside the connector, and the outer diameter size of the connector can be reduced. As a result, miniaturization of the connector can be achieved. 
     Between the corner having a large curvature and the inner circumferential surface of the other annular member, a gap corresponding to the inclination angle of the corner having a large curvature is formed. That is, at the time of fitting the pair of housings, the timing at which the inner circumferential surface of the other annular member abuts against the corner part having a large curvature of the outer circumferential surface is later than the other portion of the outer circumferential surface. As a result, the amount of wrap between the outer circumferential surface and the inner circumferential surface of the corner part having a large curvature becomes relatively smaller than the other portions, and the strain generated in the corner part having a large curvature of the outer circumferential surface is dispersed. Accordingly, it is possible to alleviate the insertion load when one of the annular members is inserted into the other annular member, which makes it possible to reduce the insertion load at the time of fitting the pair of housings. As a result, assembly workability of the connector can be improved. 
     In this case, one of the pair of housings is inserted into the other housing formed into a tubular shape, and the outer circumferential surface of one housing has at least three protruding parts for pressing the inner circumferential surface of the other housing, and the protruding parts are preferably spaced apart from each other in the circumferential direction. 
     According to configuration, since one housing inserted into the other housing is supported on the inner circumferential surface of the other housing via each protruding part, it is possible to prevent rattling of one housing, and it is possible to improve the waterproof property by satisfactorily maintaining the contact state (for example, contact angle) between the annular members. In addition, according to this, since one housing can be supported with a simple structure, the connector structure is simplified and the miniaturization of the waterproof connector is facilitated. 
     Further, the protruding part may be formed on the inner circumferential surface of the other housing, rather than the outer circumferential surface of the one housing. That is, the inner circumferential surface of the other housing has at least three protruding parts which presses the outer circumferential surface of one housing, and the protruding parts can be configured to be disposed apart from each other in the circumferential direction. 
     Advantageous Effects of the Invention 
     According to the present invention, it is possible to provide a waterproof structure for a connector that prevents degradation in waterproof performance due to plastic deformation of the connector. Further, according to the present invention, it is possible to provide a waterproof structure of a connector which enables miniaturization of the connector. Further, according to the present invention, it is possible to provide a waterproof structure of the connector which improves the assembling workability of the connector due to the small insertion load of the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of an embodiment of a waterproof connector according to the present invention. 
         FIG. 2  is a diagram of the waterproof connector of  FIG. 1  as seen from a rear side of the female connector. 
         FIG. 3  is an external perspective view of a male connector. 
         FIG. 4  is a front view of the male connector of  FIG. 3 . 
         FIG. 5  is an external perspective view of the female connector. 
         FIG. 6  is a cross-sectional view taken along the line A-A of  FIG. 2 . 
         FIG. 7  is a partial enlarged view of a frame section of  FIG. 6 . 
         FIG. 8( a )  is a partially enlarged view of a female side annular member,  FIG. 8( b )  is a cross-sectional view taken along the arrow B-B in  FIG. 8( a ) , and  FIG. 8( c )  is a cross-sectional view taken along the arrow C-C in  FIG. 8( a ) . 
         FIG. 9  is a diagram for explaining a fitting operation between the male connector and the female connector. 
         FIG. 10  is a cross-sectional view taken along arrow D-D of  FIG. 6 . 
         FIG. 11  is a cross-sectional view of another embodiment corresponding to  FIG. 10 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of a waterproof structure of a waterproof connector to which the present invention is applied will be described with reference to  FIGS. 1 to 11 . In the present embodiment, the waterproof connector mounted on an automobile, a motorcycle, or the like is described as an example, but the waterproof structure of the connector of the present invention can be applied to connectors for various purposes. 
     As illustrated in  FIGS. 1 and 2 , a waterproof connector (hereinafter referred to as a connector)  11  of the present embodiment has a male connector  13  and a female connector  15 . A male housing (the other housing)  17  of the male connector  13  and the female housing (one housing)  19  of the female connector  15  are fitted to each other in the connector  11 , thereby electrically connecting and the male terminal  21  accommodated in the male housing  17  and the female terminal  23  accommodated in the female housing  19 . An electric wire  25  is connected to the male terminal  21 , and an electric wire  27  is connected to the female terminal  23 . The female housing  19  is locked in a state of being inserted inside the male housing  17 . In the present embodiment, an example in which two terminals are accommodated in each connector will be described, but the number of accommodated terminals is not limited to two. In the following description, a X direction in  FIG. 1  is defined as a front-rear direction, a Y direction is defined as a width direction, a Z direction is defined as a height direction, and a fitting direction of the male and female connector is defined as the front, respectively. Further, an upper side of  FIG. 1  is defined as an upper part. 
     The male connector  13  has a male housing  17  formed in a tubular shape with an insulating synthetic resin, and a male terminal  21  accommodated in the male housing  17  from the rear part. As illustrated in  FIGS. 3 and 6 , in the male housing  17 , a tubular base part  31  formed with two male terminal accommodating chambers (cavities)  29  which accommodates two male terminals  21 , respectively, an electric wire holding portion  33  protruding rearward from the base part  31 , and a hood portion  35  protruding forward from the base part  31  are integrally formed. 
     The hood portion  35  is formed in a tubular shape having a circumferential wall continuous with the circumferential wall of the base part  31 , and a cross section orthogonal to the front-rear direction is an oval shape in which a width direction is a longitudinal direction. As illustrated in  FIG. 3 , the hood portion  35  has a guide groove  37  extending in the front-rear direction of the inner wall, and a plate-like wall portion  39  rising upwards to be flush with the front end surface. The wall portion  39  has a pair of first notched portions  41  formed by notching upward from the lower end, and a second notched portion which is located inside the first notched portions  41  and is notched upward from the lower end  43 . 
     The respective male terminal accommodating chambers  29  are arranged in parallel in the width direction of the male housing  17  and is formed to be partitioned by partition walls (not illustrated), and each of the male terminal accommodating chambers  29  is engaged with a male terminal  21  (not illustrated) extending inward, thereby holding (locking) the respective male terminals  21  at the setting position. As illustrated in  FIGS. 4 and 6 , each of the male terminal accommodating chambers  29  is formed by causing an opening  47  that opens to the front end surface  45  of the base part  31  surrounded by the hood portion  35 , and a through hole  49  that penetrates the wire holding portion  33  in the front-rear direction to communicate with each other in the front-rear direction. A tubular male side annular member  51  projecting forward from the periphery of the opening  47  of the front end surface  45  so as to surround the opening  47  is provided inside the hood portion  35 . The outer circumferential surface of the male side annular member  51  is disposed away from the inner circumferential surface of the hood portion  35 , and the front end surface is located behind the front end surface of the hood portion  35 . 
     As illustrated in  FIG. 3 , the male housing  17  has a lock arm  53  extending forward and supported cantilevered. The lock arm  53  has a base end portion  59  supported by a pair of wall portions  55  erected upward from both side surfaces in the width direction of the base part  31  via the leg portions  57 , and an arm portion  61  extending forward from the base end portion  59 . 
     In the lock arm  53 , the front end portion of the arm portion  61  is displaced upward in the front-rear direction with the base end portion  59  as a fulcrum. As illustrated in  FIG. 6 , a lock portion  63  protruding downward is formed in the lower portion of the front end of the arm portion  61 , thereby locking and the female housing  19  fitted in the male housing  17  via the lock portion  63 . As illustrated in  FIG. 3 , the wall portions  39  and  55  respectively positioned on the front side and on both sides the width direction of the lock arm  53  are provided to surround the lock arm  53  from the base part  31  to the hood portion  35 , and the upper end surfaces of the wall portions  39  an  55  are set at the same height as or at a position higher than the upper end surface of the lock arm  53 . 
     As illustrated in  FIG. 1 , the male terminal  21  is formed of a conductive metal plate or the like, and the wire connecting portion  65  for crimping and connecting the core wire of the electric wire  25 , and a male tub  67  connected to the female terminal  23  are integrally formed. The male tab  67  is formed in a rod shape extending in the front-rear direction, protrudes from the front end surface  45  in a state in which the male terminal  21  is locked to the lance of the male terminal accommodating chamber  29 , and is set to the length in which the leading end is positioned forward from the front end of the male side annular member  51 . 
     On the other hand, as illustrated in  FIG. 1 , the female connector  15  has a female housing  19  formed in a tubular shape with an insulating synthetic resin, and a female terminal  23  accommodated in the female housing  19  from the rear. As illustrated in  FIGS. 5 and 6 , the female housing  19  has a cross section orthogonal to the front-rear direction formed substantially similar to the inner circumferential surface of the hood portion  35  of the male housing  17 , and a base part  71  in which two female terminal accommodating chambers  69  (cavities) for housing the two female terminals  23  are formed, and an electric wire holding portion  73  which projects rearward from the base part  71  are integrally formed. Each of the female terminal accommodating chambers  69  is arranged in parallel in the width direction of the female housing  19  and is formed by being partitioned by a partition wall (not illustrated). A lance (not illustrated) extending in the female terminal accommodating chamber  69  is engaged with each female terminal  23 , thereby holding (locking) the female terminal  23  at the setting position. 
     As illustrated in  FIGS. 5 and 6 , in the female terminal accommodating chamber  69 , an opening  77  that opens the front end surface  75  of the base part  71 , and a through hole  79  penetrating the electric wire holding portion  73  in the axial direction are formed to communicate with each other in the front-rear direction. The base part  71  is provided with a tubular female side annular member  81  which projects forward from the front end surface  75  so as to surround the opening  77  from the circumferential edge of the opening  77 . The female side annular member  81  has an outer circumferential surface  81   a  in which the outer circumferential surface of the base part  71  is reduced in a stepped shape, and the outer circumferential surface  81   a  is formed to be inclined in a truncated cone shape so as to be tapered forward. In other words, the outer circumferential surface  81   a  is inclined so as to spread outward in the radial direction from the leading end toward the back (toward the base part  71 ). 
     The female housing  19  has a pair of protruding parts  83  ( FIG. 5 ) extending in the front-rear direction from the upper surface of the base part  71  and a stepped part  85  ( FIG. 6 ) extending axially from the lower surface of the base part  71 . The pair of protruding parts  83  are provided substantially parallel to each other in the width direction, and when inserting the female housing  19  into the male housing  17 , respectively, the protruding parts  83  pass through the first notched portion  41  of the male housing  17 . A locking portion  87  projecting upward is provided inside the pair of protruding parts  83 . An inclined surface  89  inclined downward toward the front is formed in the locking portion  87 . When the female housing  19  is inserted into the male housing  17 , the locking portion  87  passes through the second notched portion  43  of the male housing  17  and pushes up the arm  53  along the inclined surface  89 . 
     As illustrated in  FIG. 1 , the female terminal  23  is formed of a conductive metal plate material or the like, and a wire connection portion  91  for crimping and connecting the core wire of the electric wire  27 , and a square tubular electric contact portion  93  into which the male tab  67  of the male terminal  21  is inserted are integrally formed. In a state where the female terminal  23  is engaged with the lance of the female terminal accommodating chamber  69 , the electric contact portion  93  is positioned at a position where it is flush with the opening  77  or retracted from the opening  77  of the base part  71  by the set distance. 
     Next, the configurations of the male side annular member  51  and the female side annular member  81  will be described in detail with reference to  FIGS. 7 and 8 .  FIG. 7  is an enlarged view of the inside of the frame section of  FIG. 6 , and  FIGS. 8( a ) to 8( c )  are enlarged perspective views of the female side annular member  81 . In the present embodiment, as illustrated in  FIG. 7 , when the male housing  17  and the female housing  19  are fitted together, the female side annular member  81  is fitted inside the male side annular member  51 , and the outer circumference of the female side annular member  81  are pressed against the inner circumferential surface of the male side annular member  51  so that the annular members come into watertight contact with each other. 
     The male side annular member  51  is a resinous tubular member extending in a tubular shape from the periphery of the opening  47  of the base part  31  of the male housing  17 , and a cross section in a direction perpendicular to the front-rear direction is formed in a substantially oval shape in which the width direction is a longitudinal direction ( FIG. 3 ). The male side annular member  51  is formed such that the outer circumferential surface  51   a  and the inner circumferential surface  51   b  extend in the front-rear direction, respectively, and the thickness dimensions of the inner and outer circumferential surfaces are set to be smaller than the thickness dimensions of the inner and outer circumferential surfaces of the female side annular member  81 . Therefore, the male side annular member  51  has higher elasticity than the female side annular member  81 . A front end portion (a leading end portion) of the inner circumferential surface  51   b  of the male side annular member  51  has an inclined surface  99  which widens toward the front end surface, and the female side annular member  81  is guided toward the inner side the male annular member  51  along the inclined surface  99 . 
     The female side annular member  81  is a resinous tubular member extending in a tubular shape from the periphery of the opening  77  of the base part  71  of the female housing  19 , and the cross section in the direction orthogonal to the front-rear direction is a substantially oval shape in which the width direction is the longitudinal direction, and is substantially similar to the cross section of the inner circumferential surface  51   b  of the male side annular member  51 . An outer circumferential surface  81   a  of the female side annular member  81  is inclined in a direction in which the thickness dimension (thickness) between the inner circumferential surface  81   b  extending in the front-rear direction increases from the front end (leading end) to the back (rear). In other words, the outer circumferential surface  81   a  of the female side annular member  81  is inclined so as to spread outward in the radial direction from the front end (leading end) to the back (rear). The female side annular member  81  having the inclined outer circumferential surface  81   a  in this manner has a shape in which the outer circumferential surface  81   a  on the back side is pressed against the inner circumferential surface  51   b  of the male side annular member  51 . That is, the female side annular member  81  is formed into a truncated cone shape inclined inwardly in a tapered manner with respect to the front-rear direction over the entire circumference of the outer circumferential surface  81   a.    
     Here, the cross-sectional shape of the annular members  51  and  81  orthogonal to the front-rear direction of both the annular members will be described by taking the outer circumferential surface  81   a  of the female side annular member  81  as an example. As illustrated in  FIGS. 8( a ) to 8( c ) , the cross-sectional shape of a portion of the outer circumferential surface  81   a  of the female side annular member on the rear side (rear part), that is, the portion pressing the inner circumferential surface  51   b  of the male side annular member  51  is formed to have an upper surface  101  and a lower surface  103  extending in the width direction, both side surfaces  105  and  107  located on both sides in the width direction and formed in a gentle circular arc shape symmetrical to each other, and four corner parts  109   a  to  109   d  which is symmetrically positioned with respect to the central axis of the female side annular member  81  and has the largest curvature (the smallest radius of curvature). 
     On the other hand, the cross-sectional shape of the inner circumferential surface  51   b  of the male side annular member  51  is substantially similar to the cross-sectional shape of the outer circumferential surface  81   a  of the female side annular member  81 . Since the male side annular member  51  has elasticity and is elastically deformed along the outer circumferential surface  81   a  of the female side annular member  81 , even if the male side annular member  51  can press the inner side of the outer circumferential surface  81   a  over the entire circumferential direction, it is not limited to a similar figure. 
     In the present embodiment, as illustrated in  FIG. 7 , an inner dimension between the inner circumferential surfaces  51   b  facing each other in the height direction of the male side annular member  51  is defined as L 1 , an outer dimension in the height direction at the front end portion of the female side annular member  81  is set as L 2 , and an outer dimension between outer circumferential surfaces  81   a  in the height direction on the rear side is defined as L 3 . At this time, both the annular members are set to have a relation of L 3 &gt;L 1 &gt;L 2 , and this relationship is set over the entire circumferential direction. Accordingly, when the female side annular member  81  is inserted into the male side annular member  51 , the male side annular member  51  is elastically deformed to the outside by the inner circumferential surface  51   b  being pressed against the outer circumferential surface  81   a  of the female side annular member  81 , and the outer circumferential surface  81   a  of the female side annular member  81  is pressed inward by the restoring force of the elastic deformation. As described above, since both the annular members are pressed against each other in the entire circumferential direction within the elastic limit, water is prevented from entering between the annular members, and the waterproof performance of the connector  11  due to plastic deformation is prevented from deteriorating. 
     In the present embodiment, when the female side annular member  81  is inserted into the male side annular member  51 , the female side annular member  81  moves, while the outer circumferential surface  81   a  thereof is pressed against the inner circumferential surface  51   b  of the male side annular member  51 . At this time, the curvature of the corner parts  109   a  to  109   d  of the outer circumferential surface  81   a  is set to be larger than the other portions, and the strength is relatively high. Therefore, when the outer circumferential surface  81   a  is pressed against the inner circumferential surface  51   b,  the stress is concentrated on the corner parts  109   a  to  109   d  which are less likely to be elastically deformed than the other portions, and the insertion load of the female side annular member  81  increases. 
     As illustrated in  FIGS. 8( a ) to 8( c ) , in order to avoid an increase in the insertion load of the female side annular member  81 , in the female side annular member  81  of this embodiment, the inclination angle ( FIG. 8( b ) ) of the corner parts  109   a  to  109   d  having the largest curvature on the outer circumferential surface  81   a  with respect to the front-rear direction is set to be larger than the inclination angle of another portion ( FIG. 8( c ) ) in the circumferential direction. That is, an outer circumferential surface  81   a  against which the inner circumferential surface  51   b  of the male side annular member  51  abuts is formed on the back side (rear part), the corner parts  109   a  to  109   d  are inclined greatly toward the inside of the female side annular member  81 , and an amount of step difference between the outer circumferential surface  81   a  on both sides in the circumferential direction as approaching the front end. Thus, when the outer circumferential surface  81   a  and the inner circumferential surface  51   b  come into contact with each other, a gap according to the inclination angle of the corner parts  109   a  to  109   d  is formed between the corner parts  109   a  to  109   d  and the inner circumferential surface  51   b.  Thus, when the male housing  17  and the female housing  19  are fitted to each other, the timing at which the inner circumferential surface  51   b  of the male side annular member  51  abuts against the corner parts  109   a  to  109   d  becomes later than other portions in the circumferential direction of the outer circumferential surface  81   a.  That is, the amount of lap between the outer circumferential surface  81   a  and the inner circumferential surface  51   b  of each of the corner parts  109   a  to  109   d  is smaller than other portions in the circumferential direction, and the stress (strain) generated in the corner parts  109   a  to  109   d  is dispersed. Therefore, according to the present embodiment, it is possible to reduce the insertion load when the female side annular member  81  is inserted into the male side annular member  51 , and the assembling workability of the connector  11  can be improved. 
     Next, an example of assembling method and fitting operation of both housings will be described. First, as illustrated in  FIG. 1 , the male terminal  21  to which the electric wire  25  with the rubber stopper  111  attached thereto is connected is inserted into the male housing  17  (the male terminal accommodating chamber  29 ) together with the rubber plug  111 . The male terminal  21  inserted into the male housing  17  is engaged with a lance (not illustrated) and locked at a predetermined position in the male terminal accommodating chamber  29 . The gap between the outer circumferential surface of the electric wire passing through the male terminal accommodating chamber  29  and the inner surface of the male terminal accommodating chamber  29  is sealed by the rubber plug  111 . Similarly, the female terminal  23  to which the electric wire  27  with the rubber stopper  113  attached thereto is connected is inserted into the female housing  19  (female terminal receiving chamber  69 ) together with the rubber plug  111 . The male terminal  23  inserted into the female housing  19  is engaged with a lance (not illustrated) and locked in a predetermined position of the female terminal accommodating chamber  69 . The gap between the outer circumferential surface of the electric wire passing through the female terminal receiving chamber  69  and the inner surface of the female terminal receiving chamber  69  is sealed by the rubber plug  113 . 
     In this state, as illustrated by an arrow in  FIG. 9 , the female housing  19  of the female connector  15  is inserted into the male housing  17  of the male connector  13 . When the female housing  19  is inserted into the male housing  17 , the pair of protruding parts  83  of the female housing  19  pass through the first notched portion  41  of the male housing  17 , respectively, and the locking portion  87  of the female housing  19  passes through the second notched portion  43  of Fig. Also, the stepped part  85  of the female housing  19  is guided along the guide groove  37  of the male housing  17 . 
     When the female housing  19  is inserted into the back of the male housing  17 , the lock arm  53  is moved along the inclined surface  89  of the locking portion  87  of the female housing  19  so that the lock portion  63  climbs over the locking portion  87 , and the arm portion is bent and deformed upward. When the lock portion  63  climbs over the locking portion  87 , the arm portion  61  elastically returns. As a result, the locking portion  87  is locked to the lock portion  63 , and both the housings are locked in a proper fitted state. 
     On the other hand, when the female housing  19  is inserted to a predetermined position of the male housing  17 , insertion of the female side annular member  81  into the male side annular member  51  is started. The female side annular member  81  inserted inward along the inclined surface  99  of the male side annular member  51  moves, while the outer circumferential surface  81   a  presses the inner circumferential surface  51   b  of the male side annular member  51  and rests in a manner of pushing the inner circumferential surface  51   b  over the entire circumference. That is, the inner circumferential surface  51   b  and the outer circumferential surface  81   a  of the male side annular member  51  and the female side annular member  81  are pressed against each other over the entire circumferential direction, so that the male side annular member  51  and the female side annular member  81  are in watertight contact with each other, and water is prevented from entering the opening  47  of the male connector  13  and the opening  77  of the female connector  15 , respectively. When the housings  17  and  19  are fitted to each other, the leading end surface of the male side annular member  51  is disposed away from the front end surface  75  of the female housing  19 , and the leading end surface of the female side annular member  81  is disposed to be spaced apart from the front end surface  45  of the male housing  17 . 
     In the present embodiment, when the male connector  13  and the female connector  15  are fitted together, the male side annular member  51  is pressed from the inside by the female side annular member  81  and is pushed out within the elastic limit, so that the gap between the male side annular member  51  and the female side annular member  81  is sealed. Therefore, entry of water into the openings  47  and  77  can be prevented. As a result, it is possible to improve the waterproof property of the connector  11 . Further, by bringing the male side annular member  51  and the female side annular member  81  into direct contact with each other to form a waterproof structure, a rubber packing or the like for waterproofing becomes unnecessary, and the outer diameter size of the connector  11  can be reduced. As a result, miniaturization and cost reduction of the connector  11  can be achieved. 
     Further, in the present embodiment, since the male side annular member  51  and the female side annular member  81  are in contact with each other within the elastic limit, for example, when the connector  11  vibrates, since the male side annular member  51  and the female side annular member  81  integrally expands and contracts, it is possible to absorb vibrations with each other. Therefore, it is possible to prevent degradation over time of the connector  11  and deterioration of waterproof property due to repetition of vibration. 
     Further, in the present embodiment, the inclination angle of the corner parts  109   a  to  109   d  on the outer circumferential surface  81   a  of the female side annular member  81  is set to be larger than the inclination angle of the other portion in the circumferential direction. As a result, the amount of lap between the corner parts  109   a  to  109   d  and the inner circumferential surface  51   b  becomes relatively small, and the strain of the corner parts  109   a  to  109   d  is dispersed. Therefore, the insertion load when inserting the female side annular member  81  into the male side annular member  51  is reduced, and it is possible to reduce the insertion load at the time of fitting the pair of housings. As a result, the assembling workability of the connector  11  can be improved. 
     Further, in this embodiment, when the female housing is inserted into the male housing  17 , the pair of protruding parts  83  are guided to the first notched portion  41  of the male housing  17 , respectively, and the stepped part  85  is guided along the guide groove  37 . Thus, the insertion direction of the female housing  19  with respect to the male housing  17  is restricted, and while bringing the female side annular member  81  into contact with the set position of the male side annular member  51  at an appropriate angle, the waterproof property of the two annular members  51 ,  81  can be stably maintained. 
     The pair of protruding parts  83  and the stepped part  85  have a function of guiding the female housing  19  to a predetermined position of the male housing  17  and positioning the female housing  19  accommodated in the male housing  17 , respectively. Neither presses the inner circumferential surface of the male housing  17  nor can completely prevent rattling of the female housing  19  accommodated in the male housing  17 . 
     In this respect, in this embodiment, as illustrated in  FIG. 10 , three protruding portions  115 ,  117 , and  119  for pressing the inner circumferential surface of the male housing  17  are provided on the outer circumferential surface of the base part  71  of the female housing  19 . The protruding parts  115 ,  117 , and  119  are arranged so as to be spaced apart from each other in the circumferential direction, the protruding part  115  and the protruding part  117  are disposed in the vicinity of the pair of protruding parts  83 , respectively, and the protruding part  119  is disposed in the central part of the stepped part  85  in the width direction. Each of the protruding parts  115 ,  117  and  119  extends in the front-rear direction, and a cross section orthogonal to the front-rear direction is formed in a circular arc shape. The front end surface  121  ( FIG. 5 ) inclines toward the outer circumferential face of the base part  71 . That is, each protruding part is pushed into the male housing  17  along the inclined end surface  121 . 
     According to this, the female housing  19  inserted into the male housing  17  is supported at three positions in the circumferential direction on the inner circumferential surface of the male housing  17  via the respective protruding portions  115 ,  117 , and  119 . For this reason, the rattling of the female housing  19  is suppressed, and the contact state between the annular members  51  and  81  is maintained satisfactorily. Further, since the female housing  19  is supported by an extremely simple structure, miniaturization of the connector  11  is facilitated. At least three protruding parts may be provided, and more protruding parts may be formed if necessary. However, when the number of protruding parts increases, the frictional resistance at the time of insertion of the female housing  19  into the male housing  17  increases, and the insertion load increases. Therefore, it is preferable that the number of protruding parts is three. Similarly, the cross section orthogonal to the front-rear direction of each protruding part is not particularly limited, but in order to reduce the frictional resistance with the male housing  17 , it is preferable to have a circular arc shape. 
     Further, as illustrated in  FIG. 11 , instead of the aforementioned protruding parts  115 ,  117 , and  119 , protruding parts  123 ,  125 , and  127  which press the outer circumferential surface of the female housing  19  inserted into the male housing  17  may be formed on the inner circumferential surface of the female housings  19 , respectively. Even in this case, each of the protruding parts  123 ,  125 , and  127  is arranged to be spaced apart in the circumferential direction, and at least three protruding parts  123 ,  125  and  127  may be provided, each protruding part extends in the front-rear direction, and a cross section orthogonal to the front-read direction is formed in a circular arc shape. Even with such a configuration, miniaturization of the connector  11  is facilitated. 
     Although the embodiment to which the present invention is applied has been described above, this is merely a representative example, and the present invention can be implemented in various forms without departing from the gist thereof. 
     Here, features of the waterproof structure of the connector and the embodiment of the waterproof connector according to the present invention described above are summarized briefly in the following (1) to (3). 
     (1) A waterproof structure of a connector ( 11 ) in which cavities ( 29 ,  69 ) respectively accommodating terminals ( 21 ,  23 ) are formed respectively in a pair of housings ( 17 ,  19 ) configured to be fitted to each other, 
     wherein in each of the pair of housings, an annular member ( 51 ,  81 ) surrounding an opening of the cavity is formed to protrude in a fitting direction, 
     wherein one of the annular members ( 81 ) has a plurality of corner parts ( 109   a  to  109   d ) in which an outer circumferential surface ( 81   a ) is inclined so as to spread outward in a radial direction from a leading end to inward, 
     wherein the outer circumferential surface presses an inner circumferential surface of the other annular member ( 51 ) in fitting, and in a cross section orthogonal to the fitting direction, 
     wherein the plurality of corner parts are positioned to be symmetrical with each other with respect to a central axis of the annular member, 
     wherein a curvature of the outer circumferential surface of the plurality of corner parts is larger than a curvature of the outer circumferential surface of other portions, and 
     wherein an inclination angle of the outer circumferential surface of the corner part with respect to the fitting direction is larger than an inclination angle of the outer circumferential surface of other portions with respect to the fitting direction. 
     (2) The waterproof structure of the connector according to the above (1), 
     wherein one housing ( 19 ) of the pair of housings is configured to be inserted into the other housing ( 17 ) formed in a tubular shape, 
     wherein the outer circumferential surface of one housing has at least three protruding parts ( 115 ,  117 ,  119 ) pressing the inner circumferential surface of the other housing, and 
     wherein the protruding parts are disposed to be spaced from each other in a circumferential direction. 
     (3) The waterproof structure of the connector according to the above (1), 
     wherein one housing ( 19 ) of the pair of housings is configured to be inserted into the other housing ( 17 ) formed in a tubular shape, 
     wherein the inner circumferential surface of the other housing has at least three protruding parts ( 123 ,  125 ,  127 ) pressing the outer circumferential surface of the one housing, and 
     wherein the protruding parts are disposed to be spaced from each other in a circumferential direction. 
     While the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. 
     This application is based on Japanese Patent Application (Japanese Patent Application No. 2016-1896) filed on Jan. 7, 2016. 
     INDUSTRIAL APPLICABILITY 
     According to the waterproof structure of the connector of the present invention, it is possible to prevent deterioration of waterproof performance due to plastic deformation of the connector, to miniaturize the connector, and to reduce the insertion load of the housing, thereby improving assembling workability of the connector. The present invention which exerts this effect is useful in the technical field of connectors. 
     REFERENCE SIGNS LIST 
       11 : Waterproof connector (connector) 
       13 : Male connector 
       15 : Female connector 
       17 : Male housing (other housing) 
       19 : Female housing (one housing) 
       21 : Male terminal 
       23 : Female terminal 
       29 : Male terminal accommodating room (cavity) 
       47 ,  77 : Opening 
       51 : Male side annular member 
       69 : Female terminal accommodating chamber (cavity) 
       81 : Female side annular member 
       109   a  to  109   d : Corner part 
       115 ,  117 ,  119 ,  123 ,  125 ,  127 : Protruding part