Abstract:
A drainage structure of an electric parts accommodation box includes a drainage port formed on a bottom wall of the box, a cut-out portion that is continuous with the drainage port, a tip of which tapers off to form an acute angle, and a water-leading groove that is continuous with the tip, formed on an outer surface of the bottom wall. With this, a droplet that sticks to the water-leading groove disposed on the outer surface of the bottom wall is brought into contact with a droplet that sticks to the tip of the cut-out portion disposed on an inner surface of the bottom wall to flow out a droplet that sticks to a peripheral edge of the drainage port to the outer surface of the bottom wall. This more effectively drains liquid droplets that would otherwise remain within the box to reduce current leaks caused by such droplets coming into contact with electrical components in the box, such as closely spaced bus bars.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of Invention  
           [0002]    The present invention relates to a drainage structure of an electric parts accommodation box disposed in an engine compartment. More particularly, the present invention is intended to efficiently drain any liquid that has penetrated into a box accommodating a battery fuse mounted on a battery.  
           [0003]    2. Description of Related Art  
           [0004]    In the electric parts accommodation box disposed in an engine compartment or the like into which water penetrates, water which has penetrated into the electric parts accommodation box is drained from an opening formed in a drainage port provided on a bottom wall thereof, as disclosed in Japanese Utility Model Application Laid-Open Nos. 7-27235 and 7-3233 and Japanese Patent Application Laid-Open No.  9 - 102264 .  
           [0005]    As shown in FIG. 8A, a bottom wall  1  inclines downward toward a drainage port  1   a  to collect water inside the electric parts accommodation box to the drainage port  1   a  and discharge it to the outside.  
           [0006]    When the drainage port  1   a  is formed at the lowermost portion of the inclined bottom wall  1 , water can be drained from the drainage port  1   a  when a large amount of water has penetrated into the fuse box. On the other hand, when a small amount of water penetrates into the fuse box, as shown in FIG. 8B, droplets may stick to the periphery of the drainage port  1   a  of the bottom wall  1 . In other words, water  100  may remain on the bottom wall  1 . Therefore, the water  100  cannot be efficiently drained from the drainage port  1   a.    
           [0007]    As shown in FIG. 9, a battery terminal  3  connected to an end of a lead wire  4  is fitted on the periphery of a battery post  2  projecting from the upper surface of a battery  1 . The lead wire  4  is wired to a fuse box  5  to connect the lead wire  4  to a fuse accommodated inside the fuse box  5 .  
           [0008]    Because this kind of the fuse box is disposed in the engine compartment proximate to the battery, water penetrates into the fuse box. Thus, it is necessary to efficiently drain the water that has penetrated into the fuse box to the outside.  
           [0009]    In the fuse box  5  shown in FIG. 9A, it is necessary to connect the battery fuse and the battery  1  with each other through the lead wire  4 . Thus, much time and labor are required, and a large number of component parts are required. In addition, a large installing space is required for the fuse box  5 . There is a demand for a construction in which the fuse box  5  is directly mounted on the battery  1  to connect the battery fuse and the battery  1  to each other without using the lead wire  4 . In this case, the fuse box accommodates the battery fuse, a bus bar connected to the terminal of the battery fuse, and a battery terminal connected to the bus bar to be connectedly fitted on the periphery of the battery post of the battery.  
           [0010]    Because the fuse box is mounted on the upper surface of the battery, it is desirable to reduce the height of the fuse box as much as possible. Therefore, as shown in FIG. 9B, a gap S is very short between the bus bar  7  accommodated in the box  6  and the bottom wall  6   a  of the box  6 . However, water sticks to the periphery of the drainage port  6   b  of the bottom wall  6   a . Consequently, even a small amount of water collected in the gap S may cause a current leak or electrical short to occur between adjacent bus bars  7 A and  7 B through the water.  
         SUMMARY OF THE INVENTION  
         [0011]    The present invention has been made in view of the above-described problem. Accordingly, it is an object of the present invention to provide an electric parts accommodation box having a structure capable of draining even a small amount of water from a drainage port to prevent a current leak or electrical short from occurring between electric parts, such as bus bars, when the length of the gap between a bottom wall of the electric parts accommodation box and the electric parts is short.  
           [0012]    To achieve the object, according to the present invention, there is provided a drainage structure of an electric parts accommodation box including a drainage port formed on a bottom wall thereof; a cut-out portion, continuous with the drainage port, a tip of which tapers off to form an acute angle; and a water-leading groove, continuous with the tip, formed on an outer surface of the bottom wall. With this, a droplet that sticks to the water-leading groove disposed on the outer surface of the bottom wall is brought into contact with a droplet that sticks to the tip of the cut-out portion disposed on an inner surface of the bottom wall to flow out a droplet that sticks to a peripheral edge of the drainage port to the outer surface of the bottom wall.  
           [0013]    A thin inclined portion may be formed on the outer surface of the bottom wall toward the peripheral edge of the drainage port. The water-leading groove is formed on the inclined portion. The water-leading groove allows droplets drawn out to the outside from the tip of the cut-out portion to be drained easily from the electric parts accommodation box.  
           [0014]    Preferably, the drainage port has an approximately square central hole approximately square and a triangular cut-out portion formed at a center of at least one side of the central hole. The triangular cut-out portion is continuous with the central hole. The tip of the triangular cut-out portion is continuous with a tip of the water-leading groove.  
           [0015]    Since the central hole is continuous with the triangular cut-out portion, droplets sticking to the peripheral edge of the drainage port can be collected easily to the tip of the cut-out portion. Since the tip of the triangular cut-out portion is continuous with the tip of the water-leading groove, it is possible to smoothly drain droplets sticking to the inner surface of the bottom wall.  
           [0016]    The drainage structure of the electric parts accommodation box includes a fuse box, mounted on an upper surface of the battery box, that accommodates a battery fuse and bus bars connected to terminals of the battery fuse. With this, a battery terminal to be fixed to a periphery of a battery post projecting from the upper surface of the battery box is connected to the bus bars. Also, the drainage port and the water-leading groove are formed on a lower case of the fuse box so that water that has penetrated into the fuse box is drained from the drainage port.  
           [0017]    The drainage port and the water-leading groove are formed on a lower case of the fuse box so that water that has penetrated into the fuse box is drained from the drainage port.  
           [0018]    According to experiments conducted by the inventors, it has been demonstrated that when a droplet that sticks to the tip of the cut-out portion continuous with the drainage port disposed on the inner surface of the bottom wall of the electric parts accommodation box contacts and coalesces a droplet that sticks to a tip of the water-leading groove disposed on the outer surface of the bottom wall thereof, the droplet on the inner surface of the bottom wall is drawn out to the outer surface of the bottom wall.  
           [0019]    The fuse box, accommodating the battery fuse, has the above-described construction to reliably draining water which has collected on the inner surface of the bottom wall of the lower case thereof to the outside. Thus, it is possible to prevent a current leak from occurring between bus bars, even though the lower case and the bus bars are disposed proximately. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    Various exemplary embodiments of the present invention will be described below with reference to the drawings, wherein:  
         [0021]    [0021]FIG. 1 is an exploded perspective view showing a fuse box according to an embodiment of the present invention.  
         [0022]    [0022]FIG. 2 is a perspective view showing a state in which the fuse box is mounted on an upper surface of a battery box.  
         [0023]    [0023]FIG. 3 is a bottom view showing a lower case forming a bottom wall of the fuse box.  
         [0024]    [0024]FIG. 4 is a sectional view showing main parts of the electric parts accommodation box.  
         [0025]    [0025]FIG. 5A is a perspective view showing a drainage port.  
         [0026]    [0026]FIG. 5B is a plan view showing the drainage port.  
         [0027]    [0027]FIG. 5C is a sectional view taken along a line I-I of FIG. 5B.  
         [0028]    [0028]FIG. 6 is an explanatory view for explaining the drainage operation of the present invention.  
         [0029]    [0029]FIGS. 7A, 7B, and  7 C are schematic views showing modifications of a cutout portion of the drainage port.  
         [0030]    [0030]FIG. 8A shows a conventional drainage port.  
         [0031]    [0031]FIG. 8B shows the problem of the conventional drainage port.  
         [0032]    [0032]FIG. 9A is a perspective view showing the state of connection between a battery and a conventional fuse box accommodating a battery fuse.  
         [0033]    [0033]FIG. 9B shows the problem of the conventional fuse box. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0034]    [0034]FIGS. 1 through 6 show a first embodiment of the present invention in which a fuse box  11  is disposed on a battery box  40  mounted inside an engine compartment. A case of the fuse box  11  includes a lower case  12 , an upper case  13 , and an intermediate case  14  that fixedly accommodates a battery fuse  10 , an input-side bus bar  15  connected to a terminal of the battery fuse  10 , and an output-side bus bar  16  also connected to the terminal of the battery fuse  10 . A battery terminal  20  to be fixed to the periphery of a battery post  41  of the battery box  40  is fastened to the input-side bus bar  15  to electrically connect the battery fuse  10  to a battery. Battery post  41  projects from an upper surface of the battery box  40 .  
         [0035]    More specifically, one end of the input-side bus bar  15  overlaps an input terminal  10   b  projecting horizontally from one side of a bottom surface of a body  10   a  of the battery fuse  10 . One end of the output-side bus bar  16  overlaps an output terminal  10   c  projecting horizontally from the other side of the bottom surface of the body  10   a  of the battery fuse  10 . Screw portions  15   a  and  16   a  projecting from the input-side bus bar  15  and the output-side bus bar  16 , respectively, penetrate through a through-hole (not shown) of the input terminals  10   b  and a through-hole (not shown) of the output terminal  10   c , respectively, and are fixed with a nut N. The intermediate case  14  accommodates the battery fuse  10 , the input-side bus bar  15 , and the output-side bus bar  16 .  
         [0036]    After the input-side bus bar and the output-side bus bar are accommodated in the intermediate case, it is possible to fasten the input-side bus bar to the input terminal of the battery fuse with a bolt and fasten the output-side bus bar to the output terminal of the battery fuse with a bolt.  
         [0037]    The intermediate case  14  in which the battery fuse  10 , the input-side bus bar  15 , and the output-side bus bar  16  are disposed is mounted on the lower case  12 , and the upper case  13  is mounted on the lower case  12 . A slight gap S 1  (see FIG. 4) is generated between the intermediate case  14  and the lower case  12  in this assembling.  
         [0038]    An opening  14   a  is formed in penetration through the intermediate case  14  so that the input-side bus bar  15  and the output-side bus bar  16  can relieve radiated heat. At the position where the opening  14   a  is disposed, the lower case  12  is mountably disposed in confrontation with the intermediate case  14 .  
         [0039]    As shown in FIG. 3, a drainage port  12   a  is formed in lower case  12  at the position where the battery fuse  10  is disposed, a drainage port  12   b  is formed at the position where the input-side bus bar  15  is disposed, and a drainage port  12   c  is formed at the position where the output-side bus bar  16  is disposed. A droplet-dividing rib  12   d  having a predetermined height is projectingly formed between the drainage ports  12   a  and  12   b , between the drainage ports  12   b  and  12   c , and between the drainage ports  12   c  and  12   a.    
         [0040]    As shown in FIG. 5, the drainage port  12   a  is provided with an approximately square central hole  12   a - 1  and a generally triangular cut-out portion  12   a - 2  formed by outwardly cutting the four sides of the central hole  12   a - 1  at the central position of each side.  
         [0041]    Four upwardly inclined portions  12 B- 1  are formed toward the four sides of the central hole  12   a - 1  on a lower-side outer surface  12 B of the lower case  12 . A water-leading groove  12   a - 3  continuous with the tip of each of the cut-out portions  12   a - 2  is formed at the central position of each of the upwardly inclined portions  12 B- 1 .  
         [0042]    An inner surface  12 A of the lower case  12  at its upper side is gently declined toward the drainage port  12   a  to flow water which has collected in the lower case  12  toward the drainage port  12   a.    
         [0043]    The tip of the triangular cut-out portion  12   a - 2  of the drainage port  12   a  and the tip of the tip of the water-leading groove  12   a - 3  formed on the outer surface of the lower case  12  are continuous with each other through a thin continuous portion  12   a - 4 . Thus, the inner and outer surfaces of the lower case  12  can be made continuous with each other.  
         [0044]    The configuration of the drainage ports  12   b  and  12   c  is similar to that of the drainage port  12   a . The drainage ports  12   b  and  12   c  are formed at positions adjacent to a side wall of the lower case  12  near a lower surface thereof. Thus, cut-out portions  12   b - 2  and  12   c   2  and water-leading grooves  12   b - 3  and  12   c - 3  may be formed on two or three sides of the central hole  12   a - 1 , instead of all four sides as in the previous example.  
         [0045]    In the upper case  13 , one half serves as an opening/closing cover  13   a . A hinge  13   c  is interposed between the opening/closing cover  13   a  and another half  13   b  locked to the lower case  12  to open and close the opening/closing cover  13   a.    
         [0046]    The fuse box  11  having the above-described construction is mounted on the upper surface of the battery box  40 . The battery terminal  20  connectable to battery post  41  of battery box  40  is accommodated in the fuse box  11  and connected to the input-side bus bar  15 .  
         [0047]    More specifically, a circular-arc portion  21  of the battery terminal  20  projects from a to-be-crimped portion which is crimped to the tip of an electric wire w 1  of a power circuit. A tightening piece  22  projects from the tip of the circular-arc portion  21  at its one side, whereas a tightening piece  23  making a pair with the tightening piece  22  projects from the tip of the circular-arc portion  21  at its other side. A bolt opening (not shown) is formed on each of the tightening pieces  22  and  23 .  
         [0048]    As shown in FIG. 2, the electric wire w 1  is accommodated in an electric wire accommodation portion  14   e  of the intermediate case  14  and not extended to the position corresponding to the circular-arc portion  21  of the battery terminal  20 . The circular-arc portion  21  is exposed to the outside to fit it on the battery box  40 .  
         [0049]    The other end portion of the input-side bus bar  15  is extended to a position where the other end portion overlaps the side of the tightening piece  23  to form a connection piece  15   b  through which a bolt opening  15   b - 1  communicating with the bolt opening (not shown) of the tightening pieces  22  and  23  is formed.  
         [0050]    A screw portion  16   b  projects upward from the upper surface of the output-side bus bar  16  at an intermediate position of the other side thereof With the nut N, a terminal  25  is fastened to an end of an electric wire w 2  to be connected to a relay box (not shown).  
         [0051]    The method of fixing the fuse box  11  to the battery box  40  is described below.  
         [0052]    Initially the fuse box  11  is disposed over the battery box  40 . Then, the circular arc portion  21  of the battery terminal  20  is fitted on the periphery of the battery post  41 . With the bolt opening (not shown) of each of the tightening pieces  22 ,  23  and the bolt opening  15   b - 1  of the connection piece  15   b  of the input-side bus bar  15  overlapping each other, the bolt B is inserted through the bolt openings and fastened with the nut N. This fits circular arc portion  21  on the periphery of the battery post  41 . In this operation, the battery and the battery fuse  10  are electrically connected to each other, and the fuse box  11  is fixed to the battery box  40 . Then, the opening/closing cover  13   a  of the upper cover  13  is closed to lock the upper cover  13  to the lower cover  12 .  
         [0053]    At this time, as shown in FIG. 4, the droplet-dividing rib  12   d  projecting from the bottom wall of the lower case  12  contacts the upper surface of the battery box  40 , and a small gap S 2  is formed between the outer surface  12 B of the lower case  12  and the battery box  40 .  
         [0054]    If water penetrates into the fuse box  11  mounted on the upper surface of the battery box  40 , as described above, water collects in the small gap S 1  formed between the intermediate case  14  and the lower case  12 . In this case, water  100  flows down to the drainage ports  12   a  through  12   c  along the inner surface  12 A of the lower case  12 . If the amount of the water  100  is large, the water  100  flows out from the drainage port  12   a  and is discharged to the small gap S 2  formed between outer surface  12 B of the lower case  12  and the battery box  40 .  
         [0055]    On the other hand, if a small amount of water  100  flows to the drainage ports  12   a  through  12   c  along the inner surface  12 A of the lower case  12 , a droplet  100   a  sticks to the peripheral edge of the drainage ports  12   a  through  12   c , namely, the peripheral edge of the central hole  12   a - 1  and that of the cut-out portion  12   a - 2  and does not flow out from the drainage ports  12   a  through  12   c.    
         [0056]    At the time of the water penetration, the droplet  100   a  sticks to the outer surface  12 B of the lower case  12  and to the water-leading groove  12   a - 3 . As shown in FIG. 6, the droplet  100   a  that has stuck to the tip of the water-leading groove  12   a - 3  and the droplet  100   a  that has stuck to the tip of the cut-out portion  12   a - 2  (FIG. 2) contact each other at the thin continuous portion  12   a - 4 . When the droplet  100   a  on the outer surface  12 B of the lower case  12  and the droplet  100   a  on the inner surface  12 A thereof contact each other and coalesce therewith, the former acts in such a way as to draw out the latter from the inner surface  12 A of the lower case  12 . Consequently, the droplet  100   a  flows out through the water-leading groove  12   a - 3 .  
         [0057]    As described above, the droplet present on the outer surface of the lower case  12  contacts and coalesces the droplet that has collected in the slight gap S 1  between the intermediate case  14  and the inner surface  12 A of the lower case  12 , with the droplet sticking to the peripheral edge of the drainage ports  12   a  through  12   c  at the side of the inner surface  12 A of the lower case  12 . Thereby, it is possible to discharge the droplet to the outside through the drainage ports  12   a  through  12   c . Thus, it is possible to prevent water from collecting in the slight gap S 1  between the intermediate case  14  and the inner surface  12 A of the lower case  12 . That is, it is possible to prevent water from penetrating into the opening  14   a  of the intermediate case  14 . Thereby, it is possible to prevent a current leak or electrical short from occurring between the input-side bus bar  15  and the output-side bus bar  16 .  
         [0058]    The present invention is not limited to the above-described embodiment. For example, a drainage port  120  and a cut-out portion  121  continuous therewith may be shaped, as shown in FIGS. 7A, 7B, and  7 C. That is, it is possible to adopt any drainage port  20  having a cut-out portion  121  and a tip  121   a  tapering off to form an acute angle.  
         [0059]    The electric parts accommodation box is used not only as the fuse box, but also as boxes accommodating electric component parts. The water-leading groove continuous with the peripheral edge of the drainage port formed on the bottom wall of the electric parts accommodation box is disposed on the outer surface of the bottom wall of the electric parts accommodation box. Therefore, the droplet sticking to the tip of the water-leading groove disposed on the outer surface of the bottom wall of the electric parts accommodation box contacts and coalesces the droplet sticking to the peripheral edge of the drainage port disposed on the inner surface of the bottom wall thereof. Thereby, the droplet can be drained by drawing it out to the outer surface of the bottom wall.  
         [0060]    As apparent from the foregoing description, according to the present invention, the drainage port formed on the bottom wall of the electric parts accommodation box has the cut-out portion, the tip of which tapers off to form an acute angle and which is continuous with the central hole thereof. The water-leading groove continuous with the tip is formed on the outer surface of the bottom wall, with the tip of the water-leading groove and the peripheral edge of the drainage port continuous with each other. Therefore, the droplet sticking to the tip of the water-leading groove disposed on the outer surface of the bottom wall of the electric parts accommodation box contacts and coalesces the droplet sticking to the peripheral edge of the drainage port disposed on the inner surface of the bottom wall thereof. As a result of the coalescence of the droplets, the droplet sticking to the peripheral edge of the drainage port is guided out. In this manner, drainage can be accomplished reliably.  
         [0061]    When the electric parts accommodation box is used as the fuse box accommodating the battery fuse, the droplet sticking to the inner surface of the bottom wall of the lower case can be completely drained, even though the bottom wall of the lower case and the bus bars is narrow. Thus, it is possible to prevent a current leak from occurring between bus bars.  
         [0062]    Further since the fuse box is directly mounted on the battery box, space can be saved. The battery fuse and the battery post are connected to each other not with the lead wire but with the battery terminal. Thus, it is possible to improve reliability on the electric connection.