Abstract:
The electric connector includes a housing having an opening and a bottom, the housing being formed at the bottom with a recess, at least one electric terminal projecting through a bottom of the recess into the housing, and a seal composed of light-curing resin, the seal at least partially filling the recess therewith for hermetically sealing the electric terminal.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an electric connector including a housing, and an electric terminal projecting through a bottom of the housing into the housing and sealed therearound with light-curing resin. 
     2. Description of the Related Art 
     In an electric connector used outdoors or used in a receptacle filled with fluid, holes through which electric terminals are inserted are sealed with resin to thereby close gaps in order to prevent penetration of fluid and/or dust. Such electric connectors have been suggested, for instance, in Japanese Patent Application Publications Nos. H10(1998)-284170, 2009-181798 and 2010-267512. 
     Japanese Patent Application Publication No. H10(1998)-284170 has suggested a connector including a housing in which connection terminals are housed, and a cover which is able to open and close relative to the housing. Between the housing and cover is filled with ultraviolet-curing resin in the form of gel to thereby make gaps formed among an area in which the connection terminals and electric wires are fixedly connected with each other, the housing, and the cover fluid-tight. 
     Japanese Patent Application Publication No. 2009-181798 has suggested a connector including a housing having a sealant layer and a height judge in order to hermetically seal a plurality of holes through which contacts are inserted, formed through a bottom of the housing. The sealant layer is composed of a ultraviolet-curing resin, a resin curing at a room temperature, or a resin curing when heated. The height judge is formed at a bottom of the housing for determining an optimal height by which the sealant is filled. 
     Japanese Patent Application Publication No. 2010-267512 has suggested an optic and electric connector including a receptacle connector, and a plug housing into which the receptacle connector is fit. The plug housing is formed with a first recess in which a photoelectric transfer part which converts optic signals into electric signals and vice versa, and optical parts for transferring optic signals are arranged, and a second recess in which an electric part which processes only electric signals is arranged. After the first recess was sealed with ultraviolet-curing resin, the second recess is sealed with a resin curing when heated. 
     Hereinbelow is explained a conventional electric connector with reference to  FIGS. 1 and 2 . 
     As illustrated in  FIGS. 1 and 2 , a conventional electric connector  100  includes a box-shaped housing  110  having an opening, and a plurality of electric terminals  120  inserted into a bottom  111  of the housing  110  and projecting into the housing  110  at distal ends  121  thereof. A sealant layer  130  composed of light-curing resin is formed at the bottom  111  of the housing  110  for hermetically sealing the electric terminals  120 . Gaps formed between the electric terminals  120  and holes  112  of the housing  110  through which the electric terminals  120  are inserted are filled with the sealant layer  130  for sealing therebetween. While the electric connector  100  is being transferred on a conveyer, light-curing resin is supplied by a dispenser into an inner space  113  of the housing  110 , and then, a light is vertically irradiated onto the light-curing resin for curing the same. 
     However, the conventional electric connector  100  illustrated in  FIGS. 1 and 2  is accompanied with a problem that the sealant layer  130  may be peeled off a peripheral edge of the housing  110  at the bottom  111  thereof. 
     Since a peripheral edge  114  of the bottom  111  of the housing  110  is defined with a flat bottom  115 , and an inner wall  116  standing vertically relative to the bottom  115 , a portion of the inner space  113  in which the sealant layer  130  is formed has a constant depth. Since the portion of the inner space  113  has a constant depth, and further since light-curing resin is cured in accordance with a total amount of curing-lights irradiated by a curing-light lamp, a period of time necessary for curing the sealant layer  130  in a peripheral area  131  by means of vertically irradiated curing-lights is equal to a period of time necessary for curing the sealant layer  130  in a central area  132 . 
     If a period of time for irradiating a curing-light to the sealant layer  130  were not sufficient for the sealant layer  130  to be cured, the sealant layer  130  could not be sufficiently cured with the result of reduction in an adhesive force between the sealant layer  130  and the housing  110 . In such a case, since the sealant layer  130  broadly makes close contact with the bottom  115  in the central area  132 , the sealant layer  130  can have a sufficient adhesive force, however, since the sealant layer  130  makes contact with the bottom  115  only in a small area in the peripheral area  131  of the sealant layer  130 , the sealant layer  130  may be peeled off a periphery of the bottom  111  of the housing  110  due to radical oscillation and/or temperature fluctuations. If the peeling of the sealant layer  130  from a periphery of the bottom progresses to an area around the electric terminals  120 , it is afraid that fluid may penetrate the sealant layer  130 . In such a case, it is necessary to reduce a speed at which a conveyer transfers the electric connector  100  with the result of deterioration of a yield, unless it takes a sufficient period of time for curing light-curing resin. 
     That is, if light-curing resin of which the sealant layer  130  is composed could be cured in a short period of time, it would be possible to accomplish a high yield, and if the sealant layer  130  could be prevented from peeling off the housing  110 , it would be possible to have high reliability. 
     SUMMARY OF THE INVENTION 
     In view of the above-mentioned problems in the conventional electric connector, it is an object of the present invention to provide an electric connector which is capable of curing light-curing resin defining a sealant layer, in a short period of time to thereby prevent the sealant layer from peeling off a housing, ensuring a high yield and high reliability. 
     It is further an object of the present invention to provide a housing suitable for the above-mentioned electric connector. 
     In one aspect of the present invention, there is provided an electric connector including a housing having an opening and a bottom, the housing being formed at the bottom with a recess, at least one electric terminal projecting through a bottom of the recess into the housing, and a seal composed of light-curing resin, the seal at least partially filling the recess therewith for hermetically sealing the electric terminal. 
     Since the electric connector in accordance with the present invention is designed to include the housing having the recess which is capable of reducing a thickness of the seal in a peripheral area of a bottom of the housing, it is possible to allow a light irradiated for curing light-curing resin to reach a peripheral area of the recess. Consequently, even if a curing-light were irradiated to the seal in a short period of time, it would be possible to sufficiently cure the seal with the result that it is possible to prevent the seal from peeling off the housing. 
     It is preferable that the recess has an inclining sidewall. 
     By designing the recess to have an inclining sidewall, the recess can have a reduced depth within the inclining sidewall, and hence, it is possible to allow a curing-light to surely reach a bottom within the inclining sidewall. 
     It is preferable that the inclining sidewall has a flat surface, in which case, the recess has a gradually varying depth. 
     It is preferable that at least a part of a surface of the recess is a projecting curved surface. 
     By designing the recess to have a projecting curved surface, it is possible for the recess to have a further reduced depth, and it is further possible to increase an area in which the seal makes contact with the recess, relative to a case in which the recess has a flat inclining sidewall, with the result of enhancement in an adhesive force acting between the seal and the recess. 
     It is preferable that the projecting curved surface has such a shape that a vertically irradiated light beam does not make shade therebelow. 
     At least a part of the inclining sidewall may be designed to be continuously raised and recessed, in which case, it is possible to further increase the above-mentioned contact area with the result of further enhancement in an adhesive force acting between the seal and the recess. For instance, at least a part of a surface of the recess may be step-shaped. 
     It is preferable that each of steps has an inclining sidewall. 
     It is preferable that the recess has an area smaller than an area of the bottom of the housing when viewed vertically. 
     By so designing the recess, there exists an area between a peripheral edge of the recess and a sidewall of the housing, ensuring it possible to reduce an influence exerted by shade of a curing-light caused by an upper portion of the sidewall of the housing. 
     In another aspect of the present invention, there is provided a housing defining a part of an electric connector, the housing having an opening and a bottom and being formed at the bottom with a recess, the recess being formed at a bottom thereof with at least one hole through which an electric terminal is inserted such that the electric terminal projects into the housing, the recess being to be at least partially filled with light-curing resin for hermetically sealing the electric terminal. 
     The present invention provides the advantages set forth hereinbelow. 
     Since the electric connector in accordance with the present invention is designed to include the housing having the recess which is capable of reducing a thickness of the seal in a peripheral area of a bottom of the housing, it is possible to allow a light irradiated for curing light-curing resin to reach a peripheral area of the recess. Consequently, even if a curing-light were irradiated to the seal in a short period of time, it would be possible to sufficiently cure the seal with the result that it is possible to prevent the seal from peeling off the housing, and to ensure a high yield and high reliability. 
     The above and other objects and advantageous features of the present invention will be made apparent from the following description made with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of the conventional electric connector. 
         FIG. 2  is a cross-sectional view taken along the line D-D in  FIG. 1 . 
         FIG. 3  is a plan view of the electric connector in accordance with the first embodiment of the present invention. 
         FIG. 4  is a cross-sectional view taken along the line A-A in  FIG. 3 . 
         FIG. 5  is a schematic view of an apparatus for curing a sealant layer in the electric connector illustrated in  FIG. 3 . 
         FIG. 6  is a table showing a relation between a reaction rate of light-curing resin in dependence on a total amount of a light irradiated thereto, and a depth of the light-curing resin. 
         FIG. 7  is a plan view of the electric connector in accordance with the second embodiment of the present invention. 
         FIG. 8  is a cross-sectional view taken along the line B-B in  FIG. 7 . 
         FIG. 9  is a plan view of the electric connector in accordance with the third embodiment of the present invention. 
         FIG. 10  is a cross-sectional view taken along the line C-C in  FIG. 9 . 
         FIG. 11  is a partially enlarged view of the electric connector in accordance with a variant of the third embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments in accordance with the present invention will be explained hereinbelow with reference to drawings. In the specification, “upper” indicates a side of the housing in which an opening exists, and “lower” indicates a side of the housing in which a bottom exists. 
     First Embodiment 
     An electric connector  1  in accordance with the first embodiment, illustrated in  FIGS. 3 and 4 , is used in an electric circuit equipped in an automobile, for instance. 
     The electric connector  1  includes a housing  10 , a plurality of electric terminals  20 , and a sealant layer  30 . 
     The housing  10  has a substantially rectangular bottom  14 , and a sidewall  17  vertically standing at a periphery of the bottom  14 . An upper edge of the sidewall  17  defines an opening  11 . 
     The housing  10  is formed at the bottom  19  with a recess  15 . The recess  15  has an inclining sidewall  16 , and hence, the recess  15  has a reverse-trapezoidal cross-section. The inclining sidewall  16  has a flat surface, and defines a depth gradually reducing towards the sidewall  17  of the housing  10  from a bottom  12  of the recess  15 . 
     The recess  15  has a smaller area than an area of the bottom  14  of the housing  10  when viewed vertically, as illustrated in  FIG. 3 . Accordingly, the bottom  14  of the housing  10  can be seen as a shelf  19  only between a peripheral edge of the recess  15  and the sidewall  17  of the housing  10 . 
     The recess  15  is formed at the bottom  12  thereof with a plurality of holes  13  through which the electric terminals  20  are inserted. Each of the holes  13  has an elongated rectangular cross-section in line with a horizontal cross-section of the electric terminal  20 . 
     The electric terminal  20  is composed of thin metal plates in the form of a bar. Each of the electric terminals  20  is inserted into the hole  13  such that a distal end  21  thereof projects into an inner space  18  of the housing  10 . 
     The sealant layer  30  is composed of light-curing resin filled in the recess  15 . The sealant layer  30  seals the electric terminals  20  from surroundings. The sealant layer  30  in the first embodiment is designed to have a thickness (depth) from the bottom  12  of the recess  15  to an upper edge of the inclining sidewall  16 . It should be noted that the sealant layer  30  may be designed to have a thickness smaller than a height of the inclining sidewall  16 , if the sealant layer  30  can sufficiently seal the electric terminals  20  from the surroundings, and a sufficient adhesive force can be given between the sealant layer  30  and the housing  10 . 
     In the first embodiment, the sealant layer  30  is designed to have a thickness of about 3 mm at a center thereof. 
     As the light-curing resin, there may be used a resin which can be cured by a curing-light, for instance, an invisible light such as a ultraviolet ray and an infra-red ray, or a visible light. 
     Hereinbelow is explained how the light-curing resin in the sealant layer  30  in the electric connector  1  in accordance with the first embodiment is cured, with reference to  FIGS. 5 and 6 . 
     The light-curing resin of which the sealant layer  30  is composed is filled in the recess  15  by means of a dispenser (not illustrated), and then, is cured by means of an apparatus  50  for irradiating curing-lights, illustrated in  FIG. 5 . 
     The apparatus  50  for irradiating curing-lights includes a curing-light irradiater  51  for irradiating curing-lights, a height adjuster (not illustrated) for adjusting a height of the curing-light irradiater  51 , and a conveyer  52  for transferring the electric connectors  1 . 
     The curing-light irradiater  51  includes a lamp  511  irradiating curing-lights, a reflector  512  reflecting the curing-lights irradiated from the lamp  511 , towards each of the electric connectors  1 , and a cut filter  513  shutting out lights except the curing-lights. 
     The lamp  511  may be comprised of a metal halide lamp or a high pressure mercury lamp. 
     The curing-lights irradiated from the lamp  511  through the cut filter  513  are directed to the electric connectors  1  transferred in a direction  520  from an end of the conveyer  52  towards the other end of the conveyer  52 . The light-curing resin filled in the recess  15  in the housing  10  is cured by the curing-lights. 
     Hereinbelow is explained a relation between a reaction rate of the light-curing resin in dependence on a total amount of a curing-light irradiated thereto, and a depth of the light-curing resin, with reference to  FIG. 6 . 
     The table shown in  FIG. 6  indicates the reaction taken by the three light-curing resins each having a thickness of 1 mm, 2 mm and 3 mm when cured by curing-lights irradiated from a high pressure mercury lamp. The reaction was measured by a Fourier transform infrared spectrophotometer (FTIS). 
     As shown in  FIG. 6 , there was obtained a reaction rate of 100% to a depth of 1 mm when a total amount of curing-lights was 15,000 mJ/cm 2 . Similarly, there were obtained reaction rates of 95% and 90% to depths of 2 mm and 3 mm, respectively, when a total amount of curing-lights was 15,000 mJ/cm 2 . 
     When a total amount of curing-lights was 10,000 mJ/cm 2 , there were obtained reaction rates of 92%, 82% and 70% to depths of 1 mm, 2 mm and 3 mm, respectively. 
     When a total amount of curing-lights was 5,000 mJ/cm 2 , there were obtained reaction rates of 62%, 50% and 40% to depths of 1 mm, 2 mm and 3 mm, respectively. 
     In light of the above-mentioned measurement results, it is understood that light-curing resin having a smaller depth can be cured in a shorter period of time on the assumption that the same total amount of curing-lights is irradiated to light-curing resins. 
     Since the inclining sidewall  16  of the recess  15  upwardly inclines towards the sidewall  17  of the housing  10  from a center of the recess  15 , a curing-light can reach the recess  15  by a shorter distance at a location closer to a peripheral edge of the recess  15 . Accordingly, since light-curing resin of which the sealant layer  30  is composed can be cured more surely at a location closer to a peripheral edge of the recess, it is possible to enhance an adhesive force acting between the sealant layer  30  and the recess  15 . 
     Since it is possible to surely cure the sealant layer  30  even in a peripheral area thereof, as mentioned above, it is possible to prevent the sealant layer  30  from peeling off the recess  15 , even if curing-lights are irradiated to the light-curing resin in a short period of time. Thus, the electric connector  1  in accordance with the first embodiment provides a high yield and high reliability. 
     The sidewall  17  of the housing  10  sometimes inwardly inclines at an upper portion thereof due to a tolerance of the housing  10  and/or contraction of the housing  10  found after the housing  10  was formed. However, since the housing  10  is designed to include the shelf  19  extending between the inclining sidewall  16  and the sidewall  17  outwardly from an upper edge of the inclining sidewall  16 , even if the sidewall  17  inclines inwardly at an upper portion thereof, the shelf  19  provides a distance between the sidewall  17  and the sealant layer  30 , ensuring it possible to suppress an influence exerted by shade of curing-lights caused by an upper portion of the sidewall  17  when the lamp  511  irradiates curing-lights. 
     Second Embodiment 
     The electric connector  1 X in accordance with the second embodiment is explained hereinbelow with reference to  FIGS. 7 and 8 . Parts or elements that correspond to those of the electric connector  1  illustrated in  FIGS. 3 and 4  have been provided with the same reference numerals, and will not be explained. 
     In the electric connector  1 X in accordance with the second embodiment, as illustrated in  FIGS. 7 and 8 , the recess  15  is designed to have an inclining sidewall  16   x  having a projecting curved surface. The projecting curved surface has such a shape that a vertically irradiated light does not make shade therebelow. The sealant layer  30 X filled in the recess  15  including the inclining sidewall  16   x  having a projecting curved surface is composed of the same light-curing resin as the light-curing resin of which the sealant layer  30  illustrated in  FIGS. 3 and 4  is composed. The sealant layer  30 X is designed to have a thickness (a depth) starting from the bottom  12  of the recess  15  and terminating at an upper edge of the inclining sidewall  16   x.    
     Even if the inclining sidewall  16   x  is designed to have a projecting curved surface, the recess  15  can have a reduced depth above the inclining sidewall  16   x  with the result that light-curing resin can be surely cured above the inclining sidewall  16   x , that is, at a peripheral area of the recess  15 . 
     Furthermore, since the inclining sidewall  16   x  can be designed to have a smaller depth than a depth defined by the inclining sidewall  16  having a flat surface, illustrated in  FIG. 4 , the recess  15  including the inclining sidewall  16   x  can have a greater contact area with the sealant layer  30 X, and hence, can have a greater adhesive force with the sealant layer  30 X than the recess  15  including the flat inclining sidewall  16  illustrated in  FIG. 4 . 
     In addition, the sealant layer  30 X can have a reduced volume because the inclining sidewall  16   x  projects inwardly of the recess  15 , and accordingly, it is possible to reduce a volume of light-curing resin to be filled in the recess  15 . 
     The inclining sidewall  16   x  illustrated in  FIG. 8  is designed to have a projecting curved surface extending entirely over the inclining sidewall  16   x . It should be noted that a projecting curved surface may be formed over a part of the inclining sidewall  16   x , in which case, the remainder of the inclining sidewall  16   x  remains flat. 
     Third Embodiment 
     The electric connector  1 Y in accordance with the third embodiment is explained hereinbelow with reference to  FIGS. 9 and 10 . Parts or elements that correspond to those of the electric connector  1  illustrated in  FIGS. 3 and 4  have been provided with the same reference numerals, and will not be explained. 
     In the electric connector  1 Y in accordance with the third embodiment, as illustrated in  FIGS. 9 and 10 , the recess  15  is designed to have an entirely step-shaped inclining sidewall  16   y . The sealant layer  30 Y filled in the recess  15  including the inclining entirely step-shaped sidewall  16   x  is composed of the same light-curing resin as the light-curing resin of which the sealant layer  30  illustrated in  FIGS. 3 and 4  is composed. The sealant layer  30 Y is designed to have a thickness (a depth) starting from the bottom  12  of the recess  15  and terminating at an upper edge of the inclining sidewall  16   y.    
     The inclining sidewall  16   y  in the third embodiment is designed to have three steps, but may be designed to have one, two, four or more steps in accordance with a frame by which the housing  10   y  is formed. 
     Even if the inclining sidewall  16   y  is designed to be step-shaped, the recess  15  can have a reduced depth above the inclining sidewall  16   y  with the result that light-curing resin can be surely cured above the inclining sidewall  16   y , that is, at a peripheral area of the recess  15 . 
     Furthermore, since the inclining sidewall  16   y  can be designed to have a smaller depth than a depth defined by the inclining sidewall  16  having a flat surface, illustrated in  FIG. 4 , the recess  15  including the inclining sidewall  16   y  can have a greater contact area with the sealant layer  30 X, and hence, can have a greater adhesive force with the sealant layer  30 X than both the recess  15  including the flat inclining sidewall  16  illustrated in  FIG. 4  and the recess  15  having the inclining sidewall  16   x  illustrated in  FIG. 8 . 
       FIG. 11  illustrates a variant of the third embodiment. Though  FIG. 11  illustrates only an inclining sidewall  16   z  in an enlarged scale, the remainder is not illustrated because the remainder is identical with  FIG. 10 . 
     The inclining sidewall  16   z  illustrated in  FIG. 11  is designed to comprise a horizontally extending floor  16   za  and a sidewall  16   zb  standing from the floor  16   za . The floor  16   za  and the sidewall  16   zb  form an obtuse angle, and hence, the sidewall  16   zb  defines a downwardly inclining surface when viewed from an upper edge of the recess  15 . 
     The inclining sidewall  16   y  illustrated in  FIG. 10  is designed to have a sidewall vertically standing from a horizontal floor. In contrast, the inclining sidewall  16   z  includes the downwardly inclining sidewalls  16   zb , and hence, it is possible to ensure a sufficient adhesive force between the sealant layer  30 Z and the recess  15 , and further, to prevent generation of a shade caused by curing-lights irradiated to the floors  16   za.    
     In the electric connectors illustrated in  FIGS. 10 and 11 , the inclining sidewalls  16   y  and  16   z  are designed to be entirely step-shaped. It should be noted that the inclining sidewalls  16   y  and  16   z  may be designed to be partially step-shaped, in which case, the remainder of the inclining sidewalls  16   y  and  16   z  remain flat. 
     In the inclining sidewalls  16   y  and  16   z , the steps are designed to have a common height to thereby continuously form raised and recessed area. As an alternative, only raised areas may be formed entirely over the inclining sidewall. 
     INDUSTRIAL APPLICABILITY 
     The electric connector in accordance with the present invention can be used in fields of electronic/electric device industry and automobile industry, as an electric connector suitable for electronic and electric devices or an electric connector suitable for an electric circuit to be equipped in an automobile. 
     While the present invention has been described in connection with certain preferred embodiments, it is to be understood that the subject matter encompassed by way of the present invention is not to be limited to those specific embodiments. On the contrary, it is intended for the subject matter of the invention to include all alternatives, modifications and equivalents as can be included within the spirit and scope of the following claims. 
     The entire disclosure of Japanese Patent Application No. 2011-269185 filed on Dec. 8, 2011 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.