Abstract:
A connector having insulation for electrical connection includes a housing having a concave portion, a terminal insert-molded in the housing, a lead wire electrically coupled with the terminal, a potting material for sealing the concave portion and an insulation material. The connector uses the insulation material in contact with the potting material to cover an end of the terminal extending upward in the concave portion.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is based on and claims the benefit of priority of Japanese Patent Application No. 2004-138932 filed on May 7, 2004, the disclosure of which is incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to a sealing structure of a connector and, more specifically to a sealing structure of a terminal portion of a connector.  
       BACKGROUND OF THE INVENTION  
       [0003]     A connector portion of an electrical device such as a pressure sensor is physically affected by external conditions of temperature change combined with a splash of water or the like. A connector having a terminal used in a conventional pressure sensor is shown in  FIG. 10 . In this figure, a terminal  101  is embedded in a housing  100 . A left end of the terminal  101  is protruding from a left face of the housing  100  and is electrically connected to a pressure sensor chip  102 . A right end of the terminal  101  is protruding from the housing  100  into a connection space  103  and is connected to a lead wire  110  by a solder  111 . The terminal  101  is sealed in the connection space  103  by a sealing material  112  and is protected from a splash of water or the like.  
         [0004]     The sealing material  112  made of resin securely covers the terminal  101  when a sufficient depth d from the top end of the terminal  101  to an upper surface thereof is reserved. However, restriction on the size of the pressure sensor or the like prohibits a reservation of the sufficient depth d in the connection space.  103 . When the depth d is not sufficient, the sealing material  112  has a crack  120  as shown in  FIG. 11  caused by an iterated heat stress, or the end of the terminal  101  protrudes from the surface of the sealing material  112  as shown in  FIG. 12  because of an insufficiency of the sealing material  112 . In these cases, the splash of water on the end of the terminal  101  induces a leak current, an erroneous output of the pressure sensor or the like, and leads to corrosion of the terminal  101  and the like.  
       SUMMARY OF THE INVENTION  
       [0005]     In view of the above-described problems, it is an object of the present invention to provide a sealing structure of a terminal portion of a connector that securely seals a terminal from external disturbance.  
         [0006]     The sealing structure of the present invention is characterized by an end of a terminal having an insulation covering in a connection space filled with a sealing material. In this structure, the end of the terminal is securely covered by the covering in the connection space even when the surface of the sealing material has a crack caused by aging or the like. That is, the end of the terminal extending upward is protected by an insulation covering from being exposed from the sealing material when the sealing material is damaged on its surface, or the amount of the sealing material is insufficient.  
         [0007]     The insulation covering of the terminal may be a cap member that is put on the end of the terminal with the end inserted therein. The end of the terminal can easily be insulated when the covering is in a shape of a cap.  
         [0008]     The insulation covering of the terminal may have convex portions and concave portions on an outer circumferential surface. The insulation covering of the terminal has a wider contact area with the sealing material in this manner.  
         [0009]     The insulation covering of the terminal may have a flange on the cap member. The insulation covering is firmly fixed in the sealing material in this manner.  
         [0010]     The insulation covering of the terminal may integrally cover plural ends of the terminals when there are plural ends of the terminals in the connection space. The insulation covering can easily be disposed on the plural ends of the terminals when single body of the insulation covering covers the plural ends of the terminal.  
         [0011]     The insulation covering of the terminal may be a coating. The coating can easily cover the end of the terminal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     Other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings, in which:  
         [0013]      FIG. 1  is a vertical cross-sectional view of a pressure sensor according to a first embodiment of the present invention;  
         [0014]      FIG. 2  is a top view of a connector side housing of the pressure sensor shown in  FIG. 1  including a lead wire and its connecting portion;  
         [0015]      FIG. 3  is a top view of a cap member;  
         [0016]      FIG. 4  is a cross-sectional view of the cap member shown in  FIG. 3  along the IV-IV line;  
         [0017]      FIG. 5  is a cross-sectional view of the pressure sensor for an illustration of manufacturing steps;  
         [0018]      FIG. 6  is a cross-sectional view of the pressure sensor for an illustration of manufacturing steps;  
         [0019]      FIG. 7  is a top view of a connector side housing of the pressure sensor according to a second embodiment;  
         [0020]      FIG. 8  is a cross-sectional view of the housing shown in  FIG. 7  along the VIII-VIII line;  
         [0021]      FIG. 9  is a cross-sectional view of the connector side housing according to other embodiment;  
         [0022]      FIG. 10  is a cross-sectional view of a pressure sensor for an illustration of a background of the invention;  
         [0023]      FIG. 11  is a cross-sectional view of the connector side housing for an illustration of a problem in a conventional connector; and  
         [0024]      FIG. 12  is a cross-sectional view of the connector side housing for an illustration of a problem in a conventional connector. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     A vertical cross-sectional view of a pressure sensor according to a first embodiment of the present invention is shown in  FIG. 1 . The pressure sensor includes a pressure introduction housing  1  made of metal and a connector side housing  10  made of resin. Lead wires  23   a ,  23   b  and  23   c  on the right side of the connector side housing  10  and their connecting portions are shown in  FIG. 2 . This pressure sensor is used on an automobile for detecting fluid pressure such as a fuel pressure, an engine oil pressure or the like. Detected pressure of those fluids is translated to an electric voltage output.  
         [0026]     In  FIG. 1 , the pressure introduction housing  1  is generally in a cylindrical shape having a laterally extending body. The pressure introduction housing  1  has a screw portion on its left of an outer surface for fixing the body. The housing  1  has a six-sided bolt portion  3  on its right of the outer surface. The pressure introduction housing  1  has a through hole  4  aligned on its axis for introducing pressure. A diaphragm  5  is pressed and laser-welded to a plate  6  having a hole  6   a  at a center thereof on one end of the through hole  4 . An opening on one end of the through hole  4  is hermetically closed in this manner.  
         [0027]     The connector side housing  10  is generally in a cylindrical shape having a laterally extending body. The connector side housing  10  has a left face abutted to and caulked by a right face of the pressure introduction housing  1 .  
         [0028]     The connector side housing  10  has pins  11   a ,  11   b ,  11   c  and  11   d  embedded therein as connector terminals. The pins  11   a ,  11   b ,  11   c  and  11   d  are insert-molded in the housing  10 . The pins  10   a ,  10   b ,  10   c  and  10   d  are made of brass. The pins  11   a ,  11   b  and  11   c  are used for pressure detection and the pin  11   d  is used for inspection. The connector side housing  10  has a concave portion  12  on the left face, and left ends of the pins  11   a ,  11   b ,  11   c  and  11   d  protrude from a bottom of the concave portion  12 .  
         [0029]     A pedestal  13  is disposed at the bottom of the concave portion  12 , and a sensor chip  14  is fixed on the pedestal  13 . The sensor chip  14  has a concave portion that is formed in a decreased thickness serving as a diaphragm  14   a . A space defined by the concave portion of the sensor chip  14  and the pedestal  13  works as a standard pressure space (e.g., a vacuum space). The diaphragm  14   a  has four gauges (impurity diffused layer). The four gauges are connected to implement a full-bridge circuit. The diaphragm  14   a  is warped by a difference of pressures on both sides thereof, and piezoresistance effect of the warpage of the diaphragm  14   a  changes resistance of each gauge (impurity diffused layer). The change in resistance is detected by the full-bridge circuit. That is, a difference of voltage between two terminals of the full-bridge circuit is detected as an output of an electric signal when a predetermined amount of electric current is applied between the other two terminals of the full-bridge circuit. An amplifier formed as a signal processing circuit on the sensor chip  14  takes the difference of voltage between the two terminals outputted from the full-bridge circuit as an input signal. The input signal is amplified to be an output of the amplifier.  
         [0030]     The sensor chip  14  and ends of the pins  11   a ,  11   b ,  11   c  and  11   d  are bonded by using aluminum wires  15  for a constant current supplied to the sensor chip  14  and the output of the electric signal from the sensor chip  14 . Protruding portions of the pins  11   a ,  11   b ,  11   c  and  11   d  are sealed at the bottom of the concave portion  12  by a sealant  16 . The pressure introduction housing  1  and the connector side housing  10  are caulked to contain an oil  17  in the concave portion  12  with the diaphragm  5  hermetically sealing an opening of the concave portion  12 . The oil  17  is hermetically sealed in a space defined by the diaphragm  5  and the connector side housing  10  in the following manner. That is, pouring the oil  17  in the space first, and the connector side housing  10  is caulked by the pressure introduction housing  1  with an O ring  18  and a backup ring  19  in vacuum.  
         [0031]     The connector side housing  10  has a connection space  20  formed on the right end. An upper portion and a right side face of the connection space  20  are formed as openings. The pins  11   a ,  11   b  and  11   c  protrude from a bottom of the connection space  20  and extend in an upper direction. More specifically, the pins  11   a ,  11   b  and  11   c  extend vertically upward. The connection space  20  has a side space  21  (a concave space) formed on the left. The depth of the side space  21  is smaller than the connection space  20 . The pin  11   d  protrudes from a bottom of the side space  21  and extends upward.  
         [0032]     A grommet  22  is inserted in an opening on the right side of the connection space  20  of the connector side housing  10 . The opening is covered by the grommet  22 . The ends of lead wires  23   a ,  23   b  and  23   c  extend through the grommet  22  hermetically. Each of cable cores  24  of the lead wires  23   a ,  23   b  and  23   c  has a contact  25  (a metal fitting) caulked thereon. Each of the contact has a through hole  25   a , and pins  11   a ,  11   b  and  11   c  are inserted in the holes  25   a . The contacts  25  and the pins  11   a ,  11   b  and  11   c  are connected by using a solder  26 . The connection space  20  has insulation  27  contained therein with the grommet  22  inserted in the connection space  20 . The insulation  27  is hardened to seal the inside of the connection space  20 , that is, the pins  11   a ,  11   b  and  11   c  with its soldered portions, the lead wires  23   a ,  23   b  and  23   c , and contacts  25  are sealed. In this manner, the inside of the connection space  20  is protected from foreign matter such as water and the like. The insulation  27  is made of epoxy. The pin  11   d  in the side space  21  is also sealed by the insulation  27 .  
         [0033]     The connector side housing  10 , as described above, holds the pins  11   a ,  11   b  and  11   c  as terminals with their ends protruding in the connection space  20 , and the connection space  20  holds the pins  11   a ,  11   b  and  11   c , and lead wires  23   a ,  23   b  and  23   c  electrically connected at their ends and sealed by the hardened insulation  27 .  
         [0034]     Further, each of the pins  11   a ,  11   b  and  11   c  has a cap member  30  for insulation on its end extending upward in the connection space  20 . That is, each end of the pins  11   a ,  11   b  and  11   c  is inserted in the cap member  30  that serves as an insulating cover.  FIG. 3  shows a top view of the cap member  30 , and  FIG. 4  shows a vertical cross-sectional view of the cap member  30  along IV-IV line in  FIG. 3 .  
         [0035]     The cap member  30  shown in  FIGS. 3 and 4  is made of resin. The cap member  30  is generally in a cylindrical pillar shape, and has a hole  31  as a receptacle of the ends of the pins  11   a ,  11   b  and  11   c  at the center of the bottom surface. An outer surface of the cap member  30  has many vertically extending concavities and convexities  32  on an entire outer circumference. The cap member  30  has a flange  33  on the entire outer circumference of the lower portion for preventing the cap member  30  from coming off from the pins  11   a ,  11   b  and  11   c.    
         [0036]     The cap member  30  shown in  FIGS. 3 and 4  is put on the ends of the pins  11   a ,  11   b  and  11   c  as shown in  FIG. 1 , and the insulation  27  fills the connection space  20  to a height just below a top end of the cap member  30 . The concavities and convexities  32  on the outer surface of the cap member  30  expand a contact area of the insulation  27  on the cap member  30 . The expanded area of contact between the insulation  27  and the cap member  30  prevents the insulation  27  from exfoliating. The flange  33  on the outer surface of the cap member  30  prevents the cap member  30  from coming off. Further, the concavities and convexities  32  combined by the flange  33  on the cap member  30  benefit the tightness of seal of the insulation  27  by extending a contact surface between the insulation  27  and the cap member  30  from outside atmosphere to the pins  11   a ,  11   b  and  11   c.    
         [0037]     The material of the cap member  30  is an electric insulation material and is high in adhesiveness with the insulation  27 . The cap member  30  may easily be formed by using a resin material having thermal plasticity. The material may also be a resin material such as polybutyleneterephtalate (PBT), polyphenylene sulfide (PPS) or the like. The material may also be a rubber such as acrylic rubber, nitrile rubber or the like, or may also be a ceramic type material. The material may preferably have a similar thermal expansion coefficient to a material of the insulation  27  for the tightness of sealing.  
         [0038]     Manufacturing steps of the pressure sensor is described with reference to  FIGS. 5, 6  and  1  in order. As shown in  FIG. 5 , the diaphragm  5  is pressed on one opening of the through hole  4  in the pressure introduction housing  1  by using the plate  6 , and the diaphragm  5  and the plate  6  are laser-welded hermetically to the housing  1 . In this manner, the through hole  4  is blocked by the diaphragm  5 . The pressure introduction housing  1  is caulked to the connector side housing  10  with the oil  17  sealed therebetween. The cable cores  24  of the lead wires  23   a ,  23   b  and  23   c  extending through the grommet  22  are connected to the contacts  25  (metal fittings) at their ends by caulking. The grommet  22  is inserted in the connector side housing  10 . The pins  11   a ,  11   b  and  11   c  are inserted in the holes  25   a  of the contacts  25  when the grommet is inserted in the housing  10 . The pins  11   a ,  11   b  and  11   c  are soldered to the contacts  25  by using the solder  26 .  
         [0039]     The bridge circuit described above is inspected by an inspection signal supplied to the pin  11   d . The output of from the sensor is inspected by monitoring an amplified output signal from the sensor.  
         [0040]     Next, as shown in  FIG. 6 , each end of the pins  11   a ,  11   b  and  11   c  is press-fitted in the cap member  30 . The ends of the pins  11   a ,  11   b  and  11   c  are covered by the cap members  30 .  
         [0041]     Then, the connection space  20  of the connector side housing  10  is filled with the insulation  27 . The insulation  27  is hardened to seal the connection space  20 . The insulation  27  is poured into the connection space  20  and left at the temperature 125° C. for one hour to be hardened when the insulation  27  is made of epoxy. The insulation  27  fills the connection space  20  to a height that at least covers part of the concavities and convexities  32  on the cap member  30 . The concavities and convexities  32  along with the flange  33  contribute to sealing when they are covered by the insulation  27 .  
         [0042]     The pressure sensor manufactured in this manner has an increased tightness of sealing for the pins  11   a ,  11   b  and  11   c  covered by the cap member  30  and securely protects the pins  11   a ,  11   b  and  11   c  from external disturbance. That is, the pins  11   a ,  11   b  and  11   c  are prevented from being exposed by the cap members  30  as shown in  FIG. 1  even when thickness d of the insulation  27  shown in  FIG. 10  is not sufficient to prevent the insulation from having cracks by iterated heat stress. The exposure of the pins  11   a ,  11   b  and  11   c  caused by an insufficient amount of the insulation  27  as shown in  FIG. 12  can also be prevented by the cap member  30 . As a result, the pins  11   a ,  11   b  and  11   c  are securely protected from external water, and thus leakage of electric current, malfunction of the sensor and corrosion of internal parts are prevented.  
         [0043]     The characteristics of the first embodiment of the present invention are summarized in the following.  
         [0044]     (1) In a sealing structure of the housing  10 , the pins  11   a ,  11   b  and  11   c  are covered by the cap members  30  at their ends that extend upward in the connection space  20  as shown in  FIG. 1 . Therefore, the pins  11   a ,  11   b  and  11   c  are securely protected from external disturbance such as water by the cap members  30  even when the insulation  27  is damaged by aging or insufficiency of the insulation  27 . The pins  11   a ,  11   b  and  11   c  are otherwise exposed to the atmosphere.  
         [0045]     (2) The cap members  30  can easily be put on the ends of the pins  11   a ,  11   b  and  11   c . Therefore, the pins  11   a ,  11   b  and  11   c  can easily be covered and insulated.  
         [0046]     (3) The concavities and convexities  32  on the outer surface of the cap member  30  can extend a contact area of the insulation  27  on the cap member  30  as shown in  FIGS. 3 and 4 . Therefore, the cap member  30  can be firmly held by the insulation  27 .  
         [0047]     (4) The flange  33  on the outer surface of the cap member  30  can firmly hold the cap member  30  in the insulation  27  as shown in  FIGS. 3 and 4 . Therefore, the cap member  30  is prevented from falling out of the insulation  27 .  
         [0048]     Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.  
         [0049]     For example, the cap member  30  covers each end of the pins  11   a ,  11   b  and  11   c  separately in the first embodiment. However, the cap member  30  may cover all the ends of the pins in the connection space  20  by one body as shown in  FIGS. 7 and 8 .  FIG. 7  shows an alternative form of the cap member  30  shown in  FIG. 2 . The insulation  27  is omitted in  FIG. 7 .  FIG. 8  shows a vertical cross-section along VIII-VIII line in  FIG. 7 .  
         [0050]     The pins  11   a ,  11   b  and  11   c  in  FIGS. 7 and 8  are covered by the cap member  30  formed in one body. More practically, the flanges  33  of the cap members  30  are connected to form an integrated cap member  30  as shown in  FIGS. 7 , and  8 .  
         [0051]     The integrated cap member  30  has an increased operability. That is, the pins  11   a ,  11   b  and  11   c  protruding in the connection space  20  can more easily be covered by the integrated cap member  30  than covered by the three separate cap members  30 .  
         [0052]     The cap member  30  for insulation may be replaced with a coating  40  as shown in  FIG. 9 . The coating  40  can easily be put on the pins  11   a ,  11   b  and  11   c . Material used for the coating  40  may preferably have a similar thermal expansion coefficient to the insulation  27 . Closeness of the thermal expansion coefficient contributes to the tightness of sealing.  
         [0053]     The coating  40  may be replaced with a resin material such as poly-paraxylylene that can be deposited on the pins  11   a ,  11   b  and  11   c  and other parts in the connection space  20  by using a vacuum chamber.  
         [0054]     The pins  11   a ,  11   b  and  11   c  in the connection space  20  extend vertically upward in the first embodiment. However, the pins  11   a ,  11   b  and  11   c  may be covered by an insulating material when they extend slantingly upward in the connection space  20 .  
         [0055]     The concavities and convexities  32  along with the flange  33  are formed on the cap member  30  as shown in  FIGS. 3 and 4 . However, the cap member  30  may only have the concavities and convexities  32 , or may only have the flange  33 .  
         [0056]     Description of the embodiment so far refers to a sealing structure of terminals applied to a pressure sensor. However, the sealing structure may be applied to an acceleration sensor, a temperature sensor or the like. This structure may also be applied to an electric device other than a sensor.  
         [0057]     Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.