Abstract:
An electromagnetic shield connection mechanism according to the present invention is for a structure in which a housing wall is fixed to a equipment by inserting a bolt through a collar fitted in a hole formed on the housing wall. The electromagnetic shield connection mechanism according to the present invention is characterized in that a contact member connected to a metal shield lies between the collar and the equipment so that the collar presses the contact member tightly against the equipment, resulting in that a secure electromagnetic shielding is always achieved by thus improved contact between the metal shield and the equipment.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     This invention relates to an electromagnetic shield connection mechanism that brings a shielding portion of a connector into tight electric contact with an equipment side. 
     (2) Description of the Related Art 
     In FIGS. 11 and 12, there is shown a conventional electromagnetic shield connection mechanism disclosed in Japanese Patent Application Laid-Open H8-64306. In the mechanism, a cylindrical metal shield (not shown) is inserted into a connector housing  91  made of synthetic resin and a contact piece  93  of the metal shield is exposed from a housing wall  92  at the bottom of the housing  91 , thereby allowing the contact piece  93  to contact with an electric equipment  94  (i.e. mating side). 
     Inside the connector housing  91 , there is formed a cylindrical part (not shown) which receives a female terminal (not shown) therein. A terminal base  95  protrudes from the housing wall  92  toward the equipment side for being connected with an electric circuit of the equipment side. On the housing wall  92 , there are formed a ring-shaped groove  97  fitting an waterproof packing  96  therein and the contact piece  93  of the metal shield located inside the groove  97 . 
     The housing wall  92  of the connector housing  91  is fixed to the equipment  94  by bolts  98 , and simultaneously, the contact piece  93  is brought into contact with a connecting face (grounded) of a wall of the equipment  94 . The packing  96  is pressed into the groove  97  of the housing wall  92  and a groove  99  of the equipment  94 , thereby waterproofing the contact piece  93  and the terminal base  95 . The metal shield prevents noises from coming into the terminal  95 . Thus, a direct-mount type connector  100  is composed of the connector housing  91 , the metal shield, the terminal and the waterproof packing  96 . 
     However, regarding the above conventional mechanism for electromagnetic shield connection, since the housing wall  92  is made of synthetic resin, the housing wall  92  is bent or deformed due to a repulsion force of the packing  96 , and so on, when a significant amount of heat is applied to the housing wall  92  for a long period of time, causing a problem that contact between the contact piece  93  of the metal shield and the contacting face of the wall of the equipment  94  becomes inferior. Even if a spring characteristic is given to the contact piece  93  in order to absorb the deformation of the housing wall, no sufficient contact force is available because of the nature of the material (for example, aluminum alloy) used as the contacting face of the wall of the equipment  94 , such as a central processing unit case, i.e. a unit case of an equipment. 
     In FIG. 13, there is also shown a conventional electromagnetic shield connection mechanism disclosed in Japanese Patent Application Laid-Open H8-64306. In the mechanism, a terminal  102  having wires is received into a cylindrical housing  101  having a flange made of synthetic resin, a cylindrical metal shield  103  is formed into one united body with the housing  101  therein, and a flange of the metal shield  103  is fixed to a wall of an equipment  105  together with a flange  104  of the housing  101  using bolts  106 , thereby making a contact between the metal shield  103  and the equipment  105 . 
     A core  113  of a shielded wire  107  is crimp-connected to one side of the terminal  102 , and a terminal  109  of a wire  108  of the equipment side is rigidly connected to another side of the terminal  102  using a bolt  110 . A braided shield  111  of the shielded wire  107  is connected to the metal shield  103  via a holder  112 . 
     However, regarding the above conventional mechanism for electromagnetic shield connection, since the housing  101  made of synthetic resin lies between the metal shield  103  and the terminal  102 , a tightening force by the bolts  106  is deteriorated as the housing  101  and the flange  104  become thin when heat, vibration and impact are applied continuously, causing a problem that a contact between the metal shield  103  and the equipment  105  becomes inferior. 
     It is therefore an object of the present invention to solve the above-mentioned problems that the contact between the metal shield and the equipment side becomes inferior due to the deformation of the housing wall and/or an oxidation of the connection face of the equipment side, and to provide an electromagnetic shield connection mechanism enabling the secure electromagnetic shielding to be always achieved by improving the contact between the metal shield and the equipment side. 
     SUMMARY OF THE INVENTION 
     An electromagnetic shield connection mechanism according to the present invention is for a structure in which a housing wall is fixed to an equipment by inserting bolts through a collar fitted in holes formed on the housing wall. 
     In order to accomplish the above object, a first aspect of the present invention is to provide an electromagnetic shield connection mechanism characterized in such a manner that a contact member lies between the collar and the equipment so that the collar presses the contact member against the equipment. 
     A second aspect of the present invention is to provide the electromagnetic shield connection mechanism, wherein an electrically conductive layer on a surface of the housing is kept in contact with the contact member. 
     A third aspect of the present invention is to provide the electromagnetic shield connection mechanism, wherein the contact member has a pair of plates faced with each other, the one plate having a collar-receiving hole, the other plate having a bolt-receiving hole, and the each plate is kept in contact with the each corresponding surface of the housing wall. 
     A fourth aspect of the present invention is to provide the electromagnetic shield connection mechanism, wherein the contact member is mounted at three spots of the housing wall. 
     A fifth aspect of the present invention is to provide the electromagnetic shield connection mechanism, wherein the contact member having a bolt-receiving hole is unitedly shaped together with a metal shield. 
     A sixth aspect of the present invention is to provide the electromagnetic shield connection mechanism, wherein the metal shield is connected to a shielding portion of a shielded wire. 
     A seventh aspect of the present invention is to provide the electromagnetic shield connection mechanism, wherein the collar is composed of a flange part and a cylindrical part. 
     A eighth aspect of the present invention is to provide the electromagnetic shield connection mechanism, wherein a hollow for a scrap to be collected therein is provided at a press-fitting end of the collar. 
     According to the main aspect of the present invention, the collar presses the contact member connected to a metal shield tightly against the equipment by fastening a bolt, resulting in that a secure electromagnetic shielding is always achieved by the improved contact between the metal shield and the equipment. Even if the housing wall of the connector and the equipment wall are deformed caused by substantial heat, the electromagnetic shield connection quality does not deteriorate since the collar always presses the contact member against the equipment. Further, the contact member is closely fixed with the equipment without leaving an opening therebetween so that a possible oxidation of the equipment surface, such as an aluminum surface, is prevented, resulting in that no deterioration in quality of the electromagnetic shielding take place for a long time. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view partly in longitudinal section illustrating the first example of an electromagnetic shield connection mechanism according to the present invention. 
     FIG. 2 is a cross section taken along A—A line in FIG.  1 . 
     FIG. 3 is a top view illustrating the electromagnetic shield connection mechanism. 
     FIG. 4 is a view from arrow B (bottom view) of FIG.  1 . 
     FIG. 5 is an enlarged view of portion C in FIG.  1 . 
     FIG. 6 is a perspective view illustrating a contact member. 
     FIG. 7 is a longitudinal section illustrating the second example of an electromagnetic shield connection mechanism according to the present invention. 
     FIG. 8 is an enlarged view of portion D (a bolt not shown) in FIG.  7 . 
     FIG. 9 is an exploded perspective view illustrating the electromagnetic shield connection mechanism. 
     FIG. 10 is a perspective view illustrating a metal shield. 
     FIG. 11 is a perspective view illustrating an example of conventional electromagnetic shield connection mechanism. 
     FIG. 12 is a longitudinal section illustrating an example of conventional electromagnetic shield connection mechanism. 
     FIG. 13 is a longitudinal section illustrating another example of conventional electromagnetic shield connection mechanism. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following, the preferred embodiments of the present invention are explained with reference to the attached drawings. 
     FIGS. 1 to  6  illustrate the first example of an electromagnetic shield connection mechanism according to the present invention. 
     In FIG. 1, there are shown a connector  1 , which is directly attached to an equipment  2 , and an equipment wall  3  made of electrically conductive metal provided on the equipment  2 . The connector  1  includes a housing  4  made of synthetic resin, a cylindrical metal shield  6  (see FIG. 2) installed in a pair of cylindrical connector fitting sections  5  at the left and right of the housing  4 , and a pin-shaped male terminal  7  at the center of the metal shield  6 . 
     The connector fitting section  5  extends horizontally, the base of which is made as a continuation to a vertical base wall  8  which makes a right angle between a flange-shaped housing wall  9 . A conductive plated layer is formed on the surface of the housing  4 , i.e. the inner and outer surfaces of the connector fitting section  5 , and the outer surface of the base wall  8  and the housing wall  9 . The male terminal  7  in the connector fitting section  5  is formed in continuation to a busbar  10  in the base wall  8 , and a tab  11  at the end of the busbar  10  sticks out from a boss  12  of the housing wall  9 , being placed inside the equipment  2 . 
     As shown in FIGS. 3 and 4, the housing wall  9  is triangular-shaped, having a round hole  13  at each corner (see FIG.  5 ). A collar  14  made of electrically conductive metal is press-fitted into the each hole  13 . This formation is disclosed in Japanese Patent Application Laid-Open H9-338694. The collar  14  is composed of a ring-shaped flange  15  at the upper portion and a cylindrical portion  16  formed vertically in continuation from the flange  15  (see FIG.  5 ). The bottom surface of the flange  15  and the end surface of the cylindrical portion  16  are into contact with a contact member  17  which is made of conductive metal and is U-shaped in the longitudinal section. 
     As shown in FIG. 6, the contact member  17  is basically composed of an upper plate  19 , a lower plate  21  and a vertical side plate  22 , wherein the upper plate  19  has a large diameter collar-receiving hole  18  fitting with the cylindrical portion  16  of the collar  14 , the lower plate  21  has a small diameter bolt-receiving hole  20  to be concentric with the collar-receiving hole  18 , and the side plate  22  connects the upper plate  19  and the lower plate  21 . The upper plate  19  and the lower plate  21  are faced and paralleled with each other. 
     The end of the upper plate  19  is formed with an arcuate shape and an upward tapered guide  24  is formed at the periphery of the semicircle portion, so that the contact member  17  is easy to be mounted to the housing hole  9  (see FIG.  3 ). Since the collar-receiving hole  18  is larger than the bolt-receiving hole  20 , the upper plate  19  has more flexibility in the direction of the plate thickness than the lower plate  21 . A corner  25  at the end of the lower plate  21  is chamfered to be an arc-shaped and the lower plate  21  is touchable to the equipment wall  3  (see FIG. 1) with a large contact area. Each of the upper plate  19  and the lower plate  21  has resiliency in the direction of the plate thickness. 
     As shown in FIGS. 3 and 4, the contact member  17  is inserted into the round hole  13  at each corner of the housing wall  9 . The contact member  17  is significantly smaller than the housing wall  9  so that the insertion of the contact member  17  is very easy to be performed. The upper plate  19  and the lower plate  21  are resiliently fastened onto the upper face and the lower face of the housing wall  9 , respectively. On the upper and lower faces of the housing wall  9 , there are formed recessed portions  26  and  27 , The depth of which is shallower than the thickness of the corresponding plates  19  and  21 , respectively. The side plate  22  of the contact member  17  is in contact with the side of the housing wall  9 . 
     A conductive plated layer is formed at least on the upper and lower faces of the housing wall  9  including a bearing surface of the hollow portion of fitting  26 . The contact member  17  is in contact with the plated layer at least on the inside surface of the upper plate  19 , preferably on the inside surface of the side plate  22  as well, so that the lower plate  21  is electrically connected to the plated layer. The contact member  17  is inserted at three spots of the housing wall  9 , allowing the housing wall  9  to be in contact with the equipment wall securely without making an opening, through each contact member  17  and with three point support, resulting in that the electromagnetic shield connection between the housing wall  9  and the equipment  2  is securely achieved. 
     As shown in FIG. 5, the height of the cylindrical portion  16  of the collar  14  is set to be a sum of the plate thickness (depth of the round hole  13 ) of the housing wall  19  and the thickness of the upper plate  19  of the contact member  17 . The inner diameter of the collar-receiving hole  18  of the upper plate  19  is substantially equal to the outer diameter (maximum diameter) of the cylindrical portion  16  of the collar  14 . The upper portion  29  of the cylindrical portion  16  is recessed to be comparatively smaller diameter so as not to be in contact with the inner surface of the hole  13  of the housing wall  9 , allowing only the lower portion of the cylindrical portion  16  to be in contact with the inner surface of the hole  13 , resulting in that the press-fitting force needed is reduced. 
     The outer circumference of the lower end of the cylindrical portion  16  is chamfered at  30  for guiding to attain easy insertion. It is possible to form a conductive plated layer on the inner surface of the hole  13  of the housing wall  9 . The bolt-receiving hole  20  of the lower plate  21  of the contact member  17  is formed to be comparatively smaller in diameter than the inner diameter of the collar  14 , so that the bottom surface of the cylindrical portion  16  securely abuts against the lower plate  21  of the contact member  17 . As shown in FIG. 5, the upper plate  19  and the lower plate  21  are the same in the plate thickness and the lower plate  21  is securely pressed onto the surface of the equipment wall  3  at the bottom surface (having small area) of the cylindrical portion  16 . 
     A female screw hole  31  is formed on the equipment wall  3 . The upper face of the flange  15  of the collar  14  abuts against the head  33  of the bolt  32  while the lower face of the flange  15  abuts against the upper plate  19  of the contact member  17 . The outer width of the upper plate  19  is set to be a little larger than the outer diameter of the flange  15  which is set to be a little larger than the diameter of the bolt head  33 . The conductive collar  14  electrically connects the upper plate  19  and the lower plate  21 , contributing to an electrical conduction, thereby assisting the function of side plate  22 . Even if the collar  14  is non-conductive, the side plate  22  electrically connects the plated layer on the upper face of the housing wall  9  and the lower plate  21 , enabling grounding to the equipment side to be securely achieved. 
     As shown in FIG. 2, the metal shield  6  in a fitting chamber  34  has a plurality of resilient pieces  35  on the inner surface of the chamber  34  so as to be resiliently in contact with a metal shield of a counter side connector (not shown). The metal shield  6  is finally connected to the equipment wall  3  made of conductive metal, after passing through the plated layers of inner and outer surfaces of the connector fitting section  5 , the base wall  8  and the upper face of the housing wall  9 , then through the upper plate  19 , the side plate  22  and the lower plate  21  of the contact member  17  (see FIGS. 2,  5  and  6 ). 
     Due to a fastening force of the bolt  32 , the flange  15  of the collar  14  strongly presses the upper plate  19  of the contact member  17  against the plated layer on the housing wall  9 , then the cylindrical portion  16  of the collar  14  strongly presses the lower plate  21  against the equipment wall  3 , resulting in high quality of the electromagnetic shield connection. Even if the housing wall  9  and the equipment wall  3  are deformed caused by substantial heat, a steady electromagnetic shield connection is obtained without being affected by such a hostile environment. In addition, the contact member  17 , the housing wall  9  and the equipment wall  3  are closely fixed with each other due to heavy contact load caused by axial force of the bolt  32 . Accordingly, the oxidation of the contact portion caused by an undesirable movement of contact members, which has been a problem for a conventional electromagnetic shield connection mechanism, is prevented so that no deterioration in quality of the contact takes place for a long time. In addition, since the bolt  32  is fastened through the collar  14 , deformation, wear and damage of the housing wall  9  caused by the fastening force of the bolts  32  are substantially prevented. 
     As shown in FIG. 1, a groove  37  for fitting a ring-shaped packing  36  therein is formed at the boss  12  under the housing wall  9  so that the packing  36  is closely touched on an inner surface of the hole  38  provided at the equipment wall  3 , preventing water or the like from penetrating into the equipment  2 . The female screw hole  31  fitting with the bolt  32  is formed up to halfway in the equipment wall  3 . 
     FIGS. 7 to  10  illustrate the second example of an electromagnetic shield connection mechanism according to the present invention. 
     It is an outline of the following electromagnetic shield connection mechanism that a metal shield  42  of a connector  41  directly connected with a motor is securely connected to an equipment wall (e.g. case)  44  of an equipment (e.g. motor)  43  by fastening a bolt  46  through a collar  45 . 
     In FIGS. 7 and 9, there are shown a housing  47  made of synthetic resin having a flange-shaped housing wall  48 , a metal shield  42  insert-molded within the housing  47 , a ring-shaped connector  73  made of conductive metal connected to the metal shield  42 , a braided shield (shielding portion)  49  of a shielded wire  50  connected to the connector  73 , an waterproofing rubber stopper  51  inserted around the shielded wire  50 , a rear holder  52  made of synthetic resin to prevent the rubber stopper  51  from coming out, packings  53  and  54  stuck to an inside covering  55  of the shielded wire  50  and an inner surface of a hole  56  formed at the equipment  43 , a packing stopper  57 , and a tube  58 . 
     As shown in FIGS. 7 and 9, a connector  73  is composed of a large-diameter part  74 , a middle part  72  and a small-diameter part  75 , wherein an outer circumference surface of the large-diameter part  74  is in contact with the metal shield  42 , a small-diameter part  90  of the rubber stopper  51  is fitted into the large-diameter part  74  of the connector  73 , and the small-diameter part  75  of the connector  73  is crimp connected to the braided shield  49 . A lock  89  locks the packing stopper  57  in the housing  47 . The rear holder  52  is locked in the housing  47  by a piece  59  and a counter hole  60 . 
     As shown in FIG. 9, the housing  47  is composed of a cylindrical part  61 , a boss part  62  at an end of the cylindrical part  61 , and a flange-shaped housing wall  48  extended laterally from nearly a middle position between the cylindrical part  61  and the boss part  62 . Thus, the housing wall  48  is horizontally extended parallel to the equipment wall  44 . The housing wall  48  has a round hole  63  in which the collar  45  made of conductive metal is press-fitted. As shown in FIG. 8, the collar  45  is composed of a ring-shaped flange  64  and a cylindrical portion  65 , as is the case with the first example. The bottom end of the cylindrical portion  65  abuts against a flange-shaped contact plate  66  of the metal shield  42  (see FIG.  7 ). The metal shield  42  is pressed against the equipment wall  44  by the collar  45 . 
     As shown in FIG. 10, the metal shield is composed of a ring  68 , a step  67  and the contact plate  66  extended laterally from the bottom of the ring  68 , wherein the ring  68  is composed of a small-diameter part  69  and a large diameter part  70 , and the plate  66  has a bolt insertion hole  71 . The plate  66  is formed to have the same or small size compared to the housing wall  48  of the housing  47  (see FIG. 9) and positioned so as to abut on a lower surface of the housing wall  48 . 
     As shown in FIG. 7, the ring-shaped connector  73  is connected to an inside of the ring  68  of the metal shield  42 . The large-diameter part  74  of the connector  73  is in face contact with the small diameter part  69  of the ring  68 , while the small-diameter part  75  is crimp-connected to the braided shield  49 . The small-diameter part  75  has a piece  76 , which supports an inside covering  55  of the shielded wire  50 . 
     The upper portion of the small-diameter part  69  of the metal shield  42 , which is in close contact with the large-diameter part  74  of the connector  73 , is placed in a space  77  in the housing  47 . The lower portion of the small-diameter part  69 , the step  67  and the large-diameter part  70  are mold-shaped into one united body. The contact plate  66  is exposed and placed along the bottom surface of the housing wall  48 . The large-diameter part  70  has a hole  78  for pouring resin thereinto. 
     As shown in FIG. 8, the bolt insertion hole  71  of the contact plate  66  is formed so that the hole size is substantially the same as that of the bolt insertion hole  80  of the collar  45 . The plate  66  is placed in an opening  81  of the housing wall  48  and the bottom surface of the housing wall  48  touches the upper surface of the plate  66 . The plate  66  is pressed against the equipment wall  44  by the end surface of the cylindrical portion  65  of the collar  45 . The flange  64  of the collar  45  abuts on the upper surface of the housing wall  48 . The upper part of the cylindrical portion  65  is notched to give a small diameter there, thereby reducing a force needed when the collar  45  is press-fitted into the hole  63  of the housing wall  48 . 
     The outer circumference of the press-fitting end of the cylindrical portion  65  is notched to give a small diameter there compared to the other part of the cylindrical portion  65 , so that a ring-shaped hollow (opening)  84  for a scrap to be collected therein is provided between an outer circumference surface of this small-diameter portion  83  and that of the hole  63 . The scrap is formed as the inner wall of the hole  63  is scraped off when the collar  45  is press-fitted in the hole  63 . Thus, receiving scrap into the opening  84  prevents the following problems from taking place that the scrap is caught in between the bottom end of the cylindrical portion  65  and the plate  66  or is jammed in between the bolt  46  and the female screw hole  85 . 
     As shown in FIGS. 7 and 8, the flange  64  of the collar  45  is pressed downward by the head of the bolt  46  and the plate  66  of the metal shield  42  is strongly pressed onto the equipment wall  44  by the bottom end of the cylindrical portion  65 , resulting in that the braided shield  49  of the shielded wire  50  is securely grounded through the equipment  43 . Consequently, even if the housing wall  48  is deformed with time caused by heat and so on, the shield performance of the connector  41  is not deteriorated. The collar  45  made of metal is not influenced by heat. 
     As shown in FIG. 7, the inside covering  55  of the shielded wire  50  extends from an end of the housing  47 , a male terminal  86  is crimp connected to a core (not shown) within the covering  55  and a circuit (not shown) of the equipment side is connected to the male terminal  86 . The boss  62  at the end of the housing  47  is fitted in the hole  56  of the equipment wall  44  and the packing  54  is closely pressed onto the inner circumference of the hole  56 . Since the boss  62  is engaged in the hole  56 , the single housing wall  48  is sufficient enough to securely hold the connector  41  onto the equipment wall  44 . 
     Without using the packing  53  and the packing stopper  57 , only a packing  54  such as O-ring around the outer circumference of the boss  62  may be used. In FIG. 8, a ring-shaped opening  84  for a scrap to be collected therein may be provided by notching a circumference surface of the hole  63  of the housing wall  48  instead of notching the collar  45 . The ring-shaped opening is also applicable to the collar  14  (FIG. 5) for the first example of the present invention. The collar  45  for the second example of the present invention may have no flange. The metal shield  42  may separately be assembled in the housing  47 , instead of using the insert-molding method.