Abstract:
A first cover body has a first space defined by peripheral walls. Each of a plurality of protruded portions has a through hole, and is outwardly protruded from at least one of the peripheral walls so as to define a groove communicated with the first space and the through hole. Each of a plurality of retainers is provided with one of the protruded portions. A second cover body is fitted with the first cover body so as to close the first space, while being retained by the retainers. A plurality of projections are provided on an outer periphery of a third cover body. The third cover body is disposed in the first space such that each of the projections is fitted into the groove so as to partition the first space from the through hole.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to a waterproof structure of an electric junction box in which: a circuit board assembly, disposed within a main cover, is covered by an intermediate cover; and a part such as an electronic control unit is mounted on an outer side of the intermediate cover, and is covered with a sub cover.  
           [0002]    [0002]FIG. 4 shows one form of waterproof structure of a conventional electric junction box disclosed in Japanese Utility Model Publication No.1-76123U (cf., pages 1-2 and FIG. 2).  
           [0003]    This electric junction box  41  includes a first cover  42  and a second cover  43  both of which are made of a synthetic resin, and a circuit board assembly  44  is disposed in a space formed by the two covers  42 ,  43 , and therefore the circuit board assembly  44  is protected from external waterdrops  45 , dust and others by the covers  42 ,  43 .  
           [0004]    The first cover  42  has retaining projections  47  outwardly extended from a peripheral wall  46  thereof, and the second cover  43  has engagement holes  49  formed through an intermediate portion of a peripheral wall  48  thereof. The retaining projections  47  are engaged in the engagement holes  49 , respectively. The number of the retaining projections  47  as well as the number of the engagement holes  49  is suitably determined.  
           [0005]    The peripheral wall  48  of the second cover  43  projects (as at  50 ) like an eave beyond the peripheral wall  46  of the first cover  42 , and arch-shaped protruded portions  51  are formed integrally on the outer face of the peripheral wall  48 . Each retaining projection  47  and the associated engagement hole  49  are disposed inside the corresponding protruded portion  51 , and are protected from the external waterdrops and others. The external waterdrops  45  drop onto the protruded portion  51 , and flow along the surface of the protruded portion  51 , and drop to the exterior from the eave portion  50 , and therefore the waterdrops  45  are prevented from intruding into the interior of the covers  42 ,  43  through the engagement hole  49 .  
           [0006]    In the above structure, however, when waterdrops are blown to an opening  52  of the protruded portion  51  or when the electric junction box  41  is used, with its mounting direction turned  90  degrees, there is encountered a problem that waterdrops, introduced into the protruded portion  51 , intruded into the interior of the covers  42 ,  43  through the engagement hole  49 , and adversely affected the circuit board assembly  44 , an electronic part, etc., therein.  
           [0007]    Besides, in the case where a retaining projection for a third cover (not shown) for an external electronic control unit or the like is provided within each protruded portion  51 , an opening must be formed in a bottom portion  53  of the protruded portion  51  so as to enable the removal of a mold used in a resin-molding operation. Therefore, waterdrops are more liable to intrude into the protruded portion through the two (right and left) openings, and this encounters a problem that the waterproof performance of the electric junction box is adversely affected.  
         SUMMARY OF THE INVENTION  
         [0008]    It is therefore an object of the invention to provide a waterproof structure of an electric junction box in which protruded portions for retaining a cover are formed at a box body, and waterdrops and others are prevented from intruding into the interior of the cover (box body) through the protruded portions, thereby enhancing a waterproof performance.  
           [0009]    In order to achieve the above object, according to the invention, there is provided an electric junction box, comprising:  
           [0010]    a first cover body, having a first space defined by peripheral walls;  
           [0011]    a plurality of protruded portions, each having a through hole, and outwardly protruded from at least one of the peripheral walls so as to define a groove communicated with the first space and the through hole;  
           [0012]    a plurality of retainers, each provided with one of the protruded portions;  
           [0013]    a second cover body, fitted with the first cover body so as to close the first space, while being retained by the retainers; and  
           [0014]    a third cover body, comprising a plurality of projections provided on an outer periphery thereof, the third cover body being disposed in the first space such that each of the projections is fitted into the groove so as to partition the first space from the through hole.  
           [0015]    In such a configuration, the intrusion of waterdrops along the protruded portion of the first cover body is prevented by the projections of the third cover body. Accordingly, adverse effects, such as short-circuiting and rusting, will not be exercised on electric components disposed within the electric junction box, so that the reliability of the electrical connection of the electric junction box is enhanced over a long time period.  
           [0016]    Further, since the projections of the third cover body also serve as positioning members with respect to the first cover body, the installing operation of the third cover body can be easily and smoothly performed.  
           [0017]    Preferably, each of the retainer is a retaining projection formed in the groove so as to extend toward the first space.  
           [0018]    In such a configuration, when the third cover body is installed in the first cover body, each of the projections of the third cover body pushes the retaining projection outwards, so that the protruded portions are accordingly flexed outwards. Therefore, the installing operation of the third cover body is facilitated. When the second cover body is fitted with the first cover body, or when the second and third cover bodies are removed from the first cover body, the same advantages can be attained.  
           [0019]    Preferably, the electric junction box further comprises: a first electric equipment,. disposed between the first cover body and the third cover body; and a second electric equipment, disposed between the second cover body and the third cover body.  
           [0020]    In such a configuration, the first electric equipment is protected from foreign matters by the third cover body and the projections thereof. Further, the first electric equipment is doubly protected by the second and third cover bodies. The second electric equipment is protected by the second cover body.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein:  
         [0022]    [0022]FIG. 1 is a perspective view showing a main body of an electrical junction box according to one embodiment of the invention;  
         [0023]    [0023]FIG. 2 is a perspective view showing an intermediate cover to be mounted in the main body of FIG. 1;  
         [0024]    [0024]FIG. 3 is a perspective view showing a waterproof structure of the electric junction box; and  
         [0025]    [0025]FIG. 4 is a vertical cross-sectional view showing a waterproof structure of a related-art electric junction box. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    One preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.  
         [0027]    In this embodiment, an electric junction box  1  comprises: a main cover  2  (box body) molded with synthetic resin; a circuit board assembly  3  and a fuse block  4  which are disposed within the main cover  2 ; an intermediate cover  5  molded with synthetic resin (see FIGS. 2 and 3) provided on a sub-assembly formed by the circuit board assembly  3  and the fuse block  4 ; an electronic control unit  6  (shown in dashed lines in FIG. 3) mounted on the intermediate cover  5 ; and a sub cover  7  (shown in dashed lines in FIG. 3) covering the electronic control unit  6 .  
         [0028]    As shown in FIG. 1, the main cover  2  includes a peripheral wall defined by three side walls (left, right and rear walls)  8  to  10 , and a base wall  11  perpendicularly connected to lower edges of the side walls  8  to  10 . Protruded portions  12  having a rectangular transverse cross-section are formed on each of the three side walls  8  to  10 , and a retaining projection  14  is formed integrally within each of the protruded portions  12 , which is to be engaged with an associated engagement projection  13  of the sub cover  7  (described later) or the like.  
         [0029]    Each of the protruded portions  12  is defined by a pair of short-side wall portions  12   a  extending perpendicularly from the side wall ( 8  to  10 ), and a long-side wall portion  12   b  of a larger width interconnecting the short-side wall portions  12   a . The protruded portion  12  defines an internal space  15  having a rectangular transverse cross-section extending therethrough in an upward-downward direction, thereby forming upper and lower openings  16 ,  17 .  
         [0030]    The retaining projection  14  is formed at the upper opening  16 . More specifically, the retaining projection  14  is formed on an inner surface of the wide wall portion  12 b of the protruded portion  12 , and projects inwardly therefrom toward the inside of the main cover  2 , and opposite side edges of the retaining projection  14  are perpendicularly continuous-to the short-side wall portions  12 a of the protruded portion  12 , respectively. Since the retaining projections  14  are directed inwardly, the attaching or detaching operation of the intermediate cover  5  and the sub cover  7  with respect to the main cover  2  can be easily performed through outward elastic deformation of the protruded portions  12 .  
         [0031]    In addition to the protruded portions  12 , a pair of left and right protruded portions  18  for sliding the intermediate cover  5  are formed respectively on those portions of the left and right walls  8 ,  10  disposed near to the front end of the main cover  2 . Each of the protruded portions  18  is formed with a groove  19  having a T-shaped transverse cross section and extending in parallel with the side wall  8 ,  10 . The length of the protruded portions  12 ,  18 , the position of the retaining projections  14 , etc., are suitably determined in accordance with the size, shape, etc., of the electronic control unit  6 .  
         [0032]    The present invention is mainly aimed at enhancing the waterproof performance of the protruded portions  12  for retaining the sub-cover  7 . In FIG. 1, the direction (the upper, lower, front, rear, left and right sides). of the electric junction box  1  has no relation to the mounting direction of the electric junction. box  1 , and there are occasions when the electric junction box is used in an upside-down condition or in a  90  degree-turned condition. In this specification, for the convenience, the constructions of the various portions are explained, using the direction (the upper, lower, right and left sides) shown in FIG. 1.  
         [0033]    Each of the protruded portions  12  for retaining the sub cover  7  extends vertically from the upper end of the corresponding side wall ( 8  to  10 ) to an almost middle portion in the height direction thereof, and has the retaining projection  14  formed at the upper end thereof. This protruded portion  12  has an opening  17 , from which a mold is retracted in the molding process, at its lower end. Therefore, there is an anxiety that waterdrops, dust and others intrude into the interior of the main cover  2  (that is, the interior of the electric junction box  1 ) through the spaces  15  disposed respectively beneath the retaining projections  14 . Depending on the occasion, the retaining projection  14  may be omitted from at least one of the protruded portions  12 .  
         [0034]    In this embodiment, the projections  20  are formed at a peripheral edge of the intermediate cover  5 . Each of the projections  20  is fitted into the space  15  of one of the budge portions  12  when the intermediate cover is mounted in the main case  2 . As a result, the projections  20  partition the spaces  15  from the exterior, thereby preventing waterdrops or the like from intruding into the main body  2  through the openings  16 ,  17 .  
         [0035]    A projected length L (see FIG. 2) of each projection  20  does not always need to be equal to a recessed depth W of the space  15 , and even when the length L of the projection  20  is smaller than the depth W of the space  15 , the sufficient waterproof and moisture-proof effect is achieved. A gap may be formed between a distal end  20 a of the projection  20  and a bottom surface of the space  15  if the.projection  20  substantially closes the internal space  15 . The length L of the projection  20  need to be at least long enough to overlap the retaining projection  14  (that is, the projection  20  underlies the retaining projection  14 ).  
         [0036]    The intermediate cover  5  includes: a horizontal plate portion  21  for covering a large proportion of the circuit board assembly  3  disposed in the  20  main cover  2 ; and a block portion  22  which extends from the plate portion  21  so as to cover a front end portion of the circuit board assembly  3  and the fuse block  4 . The above described projections  20  are formed integrally at opposite (left and right) side edges and rear edge of the plate portion  21 .  
         [0037]    Specifically, two projections  20  are formed at each of the left and right side edges of the plate portion  21 , and one projection  20  is formed at the rear edge thereof. The positions and number of the projections  20  are suitably determined in accordance with the positions, number or the like of the protruded portions  12  of the main cover  2  (that is, with the positions, number or the like of the retaining portions  14  of the sub cover  7  for the electronic control unit (ECU)  6 . As shown in FIG. 1, holes  24  are formed through the plate portion  21 , so that pin-shaped terminals  23  projecting from the circuit board assembly  3  respectively pass through these holes  24  to be connected to the electronic control unit  6 .  
         [0038]    The block portion  22  projects upwardly to a level higher than the plate portion  21 , and has a female connector housing  25  formed integrally therewith.  
         [0039]    The block portion  22  is formed with, at both side faces, a pair of projections  26  each having a T-shaped transverse cross section corresponding to the shape of the groove  19  of the protruded portion  18 . When the intermediate cover  5  is mounted.in the main cover  2 , the projections  26  are slidingly fitted into the grooves  19 , thereby preventing waterdrops or the like from-intruding into the main cover  2  through the budge portions  18 . Such a configuration facilitates the mounting operation of the intermediate cover  5 .  
         [0040]    As shown in FIG. 1, the circuit board assembly  3  comprises a wiring circuit board  28  and a bus bar circuit board  29 . Wires  30 , installed on the wiring circuit board  28 , are connected to uprighted press-contacting terminals  32  of bus bars  31  provided on the bus bar circuit board  29 . A fork-shaped terminal (not shown) is projected horizontally from a front end of each bus bar  31 , and is fitted into a fuse receiving chamber  33  of the fuse block  4  to be connected to a tab terminal of a fuse  34  (see FIG. 3). A connector housing, a relay-mounting portion, or the like (not shown) are mounted integrally on the bottom wall  11  of the main cover  2 . Terminals (not shown) of the circuit board assembly  3  are disposed in these connector housing and relay-mounting portion, and are connected to a connector and relays of an external wire harness.  
         [0041]    The waterproof structure of the invention can be applied to any suitable form of electric junction box which comprises: a main cover; a circuit board assembly including one or a plurality of circuit boards and disposed within the main cover; an intermediate cover covering the circuit board assembly; electronic equipments such as an electronic control unit provided on the outside of the intermediate cover; and a sub cover covering the electronic equipments. In the case where one circuit board is used, this circuit board is connected to other electronic part or the like to form a circuit board assembly.  
         [0042]    Although the present invention has been shown and described with reference to specific preferred embodiments, various changes and modifications will be apparent to those skilled in the art from the teachings herein. Such changes and modifications as are obvious are deemed to come within the spirit, scope and contemplation of the invention as defined in the appended claims.