Abstract:
Provided is a motor driver including: a housing; an electronic component that is disposed inside the housing, and that drives or controls a motor; and a fan motor that is disposed below a top plate of the housing, and that causes air to pass from an opening in a bottom plate of the housing to an opening in the top plate. In the motor driver, an outer surface of the top plate is an inclined surface.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a motor driver including electronic components for driving or controlling a motor, and a cabinet including such electronic components. 
         [0003]    2. Description of the Related Art 
         [0004]    Some motor drivers mounted inside cabinets are equipped with a fan motor. When the fan motor is in operation, air passes through the inside of the motor driver, thereby cooling the motor driver. However, when the fan motor is in operation, mist of cutting fluid scattered from the machine tool is accumulated at the fan motor, and the cutting fluid consequently adheres to the fan motor, in some cases. The cutting fluid adhering to the fan motor drops, in the form of water drops or oil drops, down to the electronic components positioned below the fan motor in the motor driver, which may cause a breakdown of the electronic components. 
         [0005]    To address this problem, in Japanese Patent Application Laid-Open Publication No. H09-172281, a fan motor is attached so as to be inclined with respect to a horizontal plane. Further, in Japanese Patent Application Laid-Open Publication No. 2007-48946, a plane for mounting a fan motor is inclined. Accordingly, in Japanese Patent Application Laid-Open Publication No. H09-172281 and Japanese Patent Application Laid-Open Publication No. 2007-48946, cutting fluid is guided to a certain area where no electronic components are disposed. 
         [0006]    In some cases, a laterally-extending wall is disposed above a motor driver. In such a case, mist of cutting fluid sprayed from the motor driver onto the wall by a fan motor is accumulated on the wall and thereby forms a fluid pool. When a certain amount of cutting fluid is accumulated, the cutting fluid drops from the wall down to the motor driver under its own weight. Then, the cutting fluid flows into the motor driver through a gap at a top plate of the motor driver, which may cause a breakdown of the electronic components. 
         [0007]    Although fan motors are normally attached to the upper end of a motor driver, some fan motors are attached to an inner part of a motor driver with a distance from the upper end of the motor driver. In such a case, mist of cutting fluid is sprayed onto an inner surface of a top plate of the housing of the motor driver by a fan motor, and accumulated at the inner surface. Then, the cutting fluid thus accumulated drops from the inner surface of the top plate down to the electronic components in the motor driver, which may cause a breakdown of the electronic components as in the above case. 
         [0008]    The present invention has been made in view of the above circumstances, and aims to provide a motor driver and a cabinet that are capable of preventing a breakdown of electronic components mounted therein, due to cutting fluid. 
       SUMMARY OF THE INVENTION 
       [0009]    To achieve the above-described aim, a first aspect of the present invention provides a motor driver including: a housing; an electronic component that is disposed inside the housing, and that drives or controls a motor; and a fan motor that is disposed below a top plate of the housing, and that causes air to pass from an opening in a bottom plate of the housing to an opening in the top plate. In the motor driver, an outer surface of the top plate is an inclined surface. 
         [0010]    According to a second aspect, in a first aspect, part of the outer surface of the top plate, the part excluding an edge portion of the outer surface of the top plate, i.e., a center portion, is in a higher position than the edge portion. 
         [0011]    According to a third aspect, in a first aspect, part of the outer surface of the top plate, the part excluding an edge portion of the outer surface of the top plate, i.e., a center portion, is in a lower position than the edge portion. 
         [0012]    According to a fourth aspect, in a first aspect, an edge portion of the outer surface of the top plate is in a higher position than an opposite edge portion of the outer surface of the top plate. 
         [0013]    According to a fifth aspect, in a first aspect, the top plate of the housing protrudes laterally so as to be longer than the width of the rest of the housing. 
         [0014]    According to a sixth aspect, in any one of the first to fifth aspects, at least one of a groove and an elongated protrusion is provided in at least one of the outer surface of the top plate of the housing and an outer surface of a side plate of the housing. 
         [0015]    A seventh aspect provides a motor driver including: a housing; an electronic component that is disposed inside the housing, and that drives or controls a motor; and a fan motor that is disposed below a top plate of the housing, and that causes air to pass from an opening in a bottom plate of the housing to an opening in the top plate. In the motor driver, an inner surface of the top plate is an inclined surface. 
         [0016]    According to an eighth aspect, in the seventh aspect, part of the inner surface of the top plate, the part excluding an edge portion of the inner surface of the top plate, i.e., a center portion, is in a higher position than the edge portion. 
         [0017]    According to a ninth aspect, in the seventh aspect, part of the inner surface of the top plate, the part excluding an edge portion of the inner surface of the top plate, i.e., a center portion, is in a lower position than the edge portion. 
         [0018]    According to a tenth aspect, in the seventh aspect, an edge portion of the inner surface of the top plate is in a higher position than an opposite edge portion of the inner surface of the top plate. 
         [0019]    According to an eleventh aspect, in any one of the seventh to tenth aspects, at least one of a groove and an elongated protrusion is provided on an inner surface of a side plate of the housing. 
         [0020]    A twelfth aspect provides a cabinet including: a first wall that extends vertically; electronic equipment that is attached to a surface of the first wall, and that drives or controls a motor; and a second wall that is attached to the first wall above the electronic equipment and extends laterally. In the cabinet, a surface of the second wall, the surface facing the electronic equipment, is an inclined surface. 
         [0021]    According to a thirteenth aspect, in the twelfth aspect, the cabinet further includes an inverted V-shaped protrusion that is provided in the first wall and is inclined downward from a portion of the first wall, the portion being other than an edge portion of the first wall, i.e., a center portion, to each side portion of the first wall. 
         [0022]    According to a fourteenth aspect, in the twelfth aspect, the cabinet further includes an elongated protrusion that is provided in the first wall and is inclined from a side portion of the first wall to an opposite side portion of the first wall. 
         [0023]    According to a fifteenth aspect, in any one of the twelfth to fourteenth aspects, the cabinet further includes a cross-sectionally U-shaped member that is provided in the first wall and extends laterally. 
         [0024]    The detailed description of the representative embodiments of the present invention illustrated in the accompanied drawings will make further clear the above objects, features, and advantages, as well as other objects, features, and advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1A  is a perspective view of a motor driver according to a first embodiment of the present invention. 
           [0026]      FIG. 1B  is a side view of the motor driver illustrated in  FIG. 1A . 
           [0027]      FIG. 10  is a schematic side view of part of the motor driver illustrated in  FIG. 1A . 
           [0028]      FIG. 2A  is a perspective view of another motor driver according to the first embodiment of the present invention. 
           [0029]      FIG. 2B  is a side view of the motor driver illustrated in  FIG. 2A . 
           [0030]      FIG. 3A  is a perspective view of still another motor driver according to the first embodiment of the present invention. 
           [0031]      FIG. 3B  is a side view of the motor driver illustrated in  FIG. 3A . 
           [0032]      FIG. 4A  is a perspective view of a motor driver similar to the one illustrated in  FIG. 1A . 
           [0033]      FIG. 4B  is a side view of the motor driver illustrated in  FIG. 4A . 
           [0034]      FIG. 4C  is a side view of a different motor driver according to the first embodiment of the present invention. 
           [0035]      FIG. 4D  is a view illustrating a modified example of the motor driver illustrated in  FIG. 4C . 
           [0036]      FIG. 5A  is a perspective view of a still different motor driver according to the first embodiment of the present invention. 
           [0037]      FIG. 5B  is another perspective view of the motor driver illustrated in  FIG. 5A . 
           [0038]      FIG. 6A  is a perspective view of an additional motor driver according to the first embodiment of the present invention. 
           [0039]      FIG. 6B  is another perspective view of the motor driver illustrated in  FIG. 6A . 
           [0040]      FIG. 7A  is a perspective view of a still additional motor driver according to the first embodiment of the present invention. 
           [0041]      FIG. 7B  is a side view of the motor driver illustrated in  FIG. 7A . 
           [0042]      FIG. 8A  is a perspective view of a motor driver according to a second embodiment of the present invention. 
           [0043]      FIG. 8B  is a side view of the motor driver illustrated in  FIG. 8A . 
           [0044]      FIG. 8C  is a schematic side view of part of the motor driver illustrated in  FIG. 8A . 
           [0045]      FIG. 9A  is a perspective view of another motor driver according to the second embodiment of the present invention. 
           [0046]      FIG. 9B  is a side view of the motor driver illustrated in  FIG. 9A . 
           [0047]      FIG. 10A  is a perspective view of still another motor driver according to the second embodiment of the present invention. 
           [0048]      FIG. 10B  is a side view of the motor driver illustrated in  FIG. 10A . 
           [0049]      FIG. 11A  is a perspective view of a different motor driver according to the second embodiment of the present invention. 
           [0050]      FIG. 11B  is a side view of the motor driver illustrated in  FIG. 11A . 
           [0051]      FIG. 12A  is a perspective view of a cabinet according to the present invention. 
           [0052]      FIG. 12B  is a side view of the cabinet illustrated in  FIG. 12A . 
           [0053]      FIG. 12C  is a side view of a cabinet similar to the one illustrated in  FIG. 12A . 
           [0054]      FIG. 12D  is a side view of another cabinet similar to the one illustrated in  FIG. 12A . 
           [0055]      FIG. 13A  is a schematic side view of part of another cabinet according to the present invention. 
           [0056]      FIG. 13B  is a perspective view of the cabinet illustrated in  FIG. 13A . 
           [0057]      FIG. 13C  is a side view of the cabinet illustrated in  FIG. 13A . 
           [0058]      FIG. 14A  is a perspective view of another cabinet according to the present invention. 
           [0059]      FIG. 14B  is a back view of the cabinet illustrated in  FIG. 14A . 
           [0060]      FIG. 15A  is a perspective view of still another cabinet according to the present invention. 
           [0061]      FIG. 15B  is a back view of the cabinet illustrated in  FIG. 15A . 
           [0062]      FIG. 16A  is a perspective view of a different cabinet according to the present invention. 
           [0063]      FIG. 16B  is a side view of the cabinet illustrated in  FIG. 16A . 
       
    
    
     DETAILED DESCRIPTION 
       [0064]    Embodiments of the present invention will be described below with reference to the accompanying drawings. Throughout the following drawings, the same parts are denoted by the same reference numerals and characters. To make it easier to understand, the drawings vary in scale as appropriate. 
         [0065]      FIG. 1A  is a perspective view of a motor driver according to a first embodiment of the present invention, and  FIG. 1B  is a side view of the motor driver illustrated in  FIG. 1A . It is assumed that a motor driver  10  illustrated in  FIGS. 1A and 1B  is placed near a machine tool or an industrial robot for cutting a workpiece (not illustrated). 
         [0066]    The motor driver  10  mainly includes a housing  20  in a substantially rectangular parallelepiped shape, and a printed circuit board  35  arranged vertically in the housing  20 . As illustrated in  FIGS. 1A and 1B , a plurality of electronic components  36  for driving or controlling a servo motor for the machine tool or the industrial robot are mounted on the printed circuit board  35 . 
         [0067]    As can be seen from  FIGS. 1A and 1B , a through-hole  28  is formed in a top plate  21  of the housing  20 . A fan motor  30  is attached to an inner surface  21   b  of the top plate  21  so as to be adjacent to the through-hole  28 . In addition, a plurality of through-holes  29  are formed in a bottom plate  22  of the housing  20 . 
         [0068]    With this configuration, when the fan motor  30  is in operation, the outside air flows into the internal space of the housing  20  through the through-holes  29  in the bottom plate  22 , and then flows out through the through-hole  28  in the top plate  21 . In this way, the electronic components  36  on the printed circuit board  35  can be cooled. 
         [0069]      FIG. 10  is a schematic side view of part of the motor driver illustrated in  FIG. 1A . As illustrated in  FIG. 10 , a wall  41 , such as a ceiling, extends approximately horizontally, above the motor driver  10 . Since the motor driver  10  is placed near a machine tool or an industrial robot as mentioned previously, cutting fluid used for machining exists around the motor driver  10  in the form of cutting fluid mist. As a result, when the fan motor  30  is in operation, the cutting fluid mist comes into the housing  20  through the through-holes  29 , and is then discharged from the internal space of the housing  20  through the through-hole  28  as indicated by a white arrow. The cutting fluid mist thus discharged is sprayed onto the wall  41  and then accumulated as a fluid pool  39 . When the fluid pool  39  reaches a certain volume, the cutting fluid drops down to the motor driver  10  under its own weight, as indicated by solid-line arrows. 
         [0070]    In some examples of the first embodiment of the present invention, an outer surface of the top plate  21  of the housing  20  is configured by two inclined surfaces  21   a . As illustrated in  FIG. 1A , each of the inclined surfaces  21   a  is inclined upward toward the center of the housing  20 . Accordingly, a line  21   d  of intersection of the inclined surfaces  21   a , which extends in parallel with each side plate of the housing  20 , is in a higher position than edge portions of the outer surface of the top plate  21 . 
         [0071]    In this configuration, even if the cutting fluid sprayed onto the wall  41  positioned above the motor driver  10  drops down to the motor driver  10 , the cutting fluid is guided to the outer surfaces of the side surfaces of the housing  20  along the inclined surfaces  21   a . This can prevent the cutting fluid from flowing into the motor driver  10 , and consequently prevent a breakdown of the electronic components  36  in the motor driver  10 , due to the cutting fluid. 
         [0072]      FIG. 2A  is a perspective view of another motor driver according to the first embodiment of the present invention, and  FIG. 2B  is a side view of the motor driver illustrated in  FIG. 2A . In  FIGS. 2A and 2B , each of two inclined surfaces  21   a  of the top plate  21  of the housing  20  is inclined downward toward the center of the housing  20 . Accordingly, a line  21   d  of intersection of the inclined surfaces  21   a , which extends in parallel with each side plate of the housing  20 , is in a lower position than the edge portions of the outer surface of the top plate  21 . 
         [0073]    In this configuration, even if cutting fluid sprayed onto the wall  41  (see  FIG. 1C ) drops down to the motor driver  10 , the cutting fluid is guided to an area near the intersection line  21   d  on the top plate  21  of the housing  20 , along the inclined surfaces  21   a , and then discharged outside the housing  20 . Thus, this configuration can prevent a breakdown of the electronic components  36  in the motor driver  10 , due to the cutting fluid. Naturally, the two inclined surfaces  21   a  may be designed to differ in size so that the intersection line  21   d  is in a position apart from the electronic components  36 . 
         [0074]      FIG. 3A  is a perspective view of still another motor driver according to the first embodiment of the present invention, and  FIG. 3B  is a side view of the motor driver illustrated in  FIG. 3A . In  FIGS. 3A and 3B , the outer surface of the top plate  21  of the housing  20  is configured by a single inclined surface  21   a . As can be seen from  FIGS. 3A and 3B , an edge portion  21   e  of the single inclined surface  21   a  is in a higher position than an opposite edge portion  21   f  of the single inclined surface  21   a.    
         [0075]    In this configuration, even if cutting fluid sprayed onto the wall  41  (see  FIG. 1C ) drops down to the motor driver  10 , the cutting fluid is guided to an outer surface  23   a  of a corresponding side plate  23  of the housing  20  with respect to the top plate  21 , along the inclined surface  21   a . Thus, it is apparent that this configuration can provide an effect similar to that described above. 
         [0076]      FIG. 4A  is a perspective view of a motor driver similar to the one illustrated in  FIG. 1A , and  FIG. 4B  is a side view of the motor driver illustrated in  FIG. 4A . In the configuration illustrated in  FIGS. 4A and 4B , a top plate  21  is attachable to and detachable from the remaining part of a housing  20 . In other words, the top plate  21  functions as a lid of the housing  20 . In addition, as can be seen from  FIG. 4B , each of edge portions  21   e  and  21   f  of the top plate  21  flushes with an outer surface of a corresponding side plate of the housing  20 . 
         [0077]    Moreover,  FIG. 4C  is a side view of a different motor driver according to the first embodiment of the present invention. In  FIG. 4C , each of edge portions  21   e  and  21   f  of the top plate  21  protrudes sideward from the outer surface of the corresponding side plate of the housing  20 . Furthermore, in  FIG. 4D  illustrating a modified example of the configuration illustrated in  FIG. 4C , each of edge portions  21   e  and  21   f  of the top plate  21  protrudes sideward and then extends downward along the outer surface of the corresponding side plate of the housing  20 . 
         [0078]    In each of these configurations, the edge portions  21   e  and  21   f  of the top plate  21  protrude sideward from the respective outer surfaces of the side plates. Consequently, even if cutting fluid sprayed onto the wall  41  (see  FIG. 1C ) drops down to the motor driver  10 , the cutting fluid is guided to the edge portions  21   e  and  21   f  of the top plate  21 . In this way, the cutting fluid is prevented from flowing into the housing  20  from a gap between the top plate  21  and the remaining part of the housing  20 . Thus, it is apparent that these configurations can provide an effect similar to that described above. By contrast, when the distance between the edge portions  21   e  and  21   f  of the top plate  21  is smaller than that between the outer surfaces of the respective side plates of the housing  20 , cutting fluid may flow into the internal space of the housing  20  from a gap between the top plate  21  and the remaining surfaces of the housing  20 . 
         [0079]      FIG. 5A  is a perspective view of a still different motor driver according to the first embodiment of the present invention, and  FIG. 5B  is another perspective view of the motor driver illustrated in  FIG. 5A . In  FIGS. 5A and 5B , two grooves  51   a  are formed in each of the two inclined surfaces  21   a . Moreover,  FIG. 6A  is a perspective view of an additional motor driver according to the first embodiment of the present invention, and  FIG. 6B  is another perspective view of the motor driver illustrated in  FIG. 6A . In  FIGS. 6A and 6B , two protrusions  52   a  are formed on each of the two inclined surfaces  21   a.    
         [0080]    As can be seen from  FIGS. 5A ,  5 B,  6 A, and  6 B, the grooves  51   a  and the protrusions  52   a  each extend from a middle area of the corresponding inclined surface  21   a  in an inclined direction with respect to the intersection line  21   d , and end at the corresponding one of the edge portions  21   e  and  21   f  of the corresponding inclined surface  21   a , the edge portions  21   e  and  21   f  being parallel with the intersection line  21   d . In addition, the two grooves  51   a  and the two protrusions  52   a  of each of the inclined surfaces  21   a  extend in directions different from each other. However, the two grooves  51   a  and the two protrusions  52   a  of each of the inclined surfaces  21   a  may extend in parallel with each other. 
         [0081]    In  FIGS. 5A ,  5 B,  6 A, and  6 B, the grooves  51   a  or the protrusions  52   a  are formed in/on the inclined surfaces  21   a  of the top plate  21 . Consequently, even if cutting fluid sprayed onto the wall  41  (see  FIG. 1C ) drops down to the motor driver  10 , the cutting fluid is guided to the outer surfaces of the side plates of the housing  20 , along the grooves  51   a  or the protrusions  52   a . Thus, it is apparent that these configurations can provide an effect similar to that described above. Note that a case in which the inclined surfaces  21   a , where the grooves  51   a  or the protrusions  52   a  are formed, are level surfaces is also within the scope of the present invention. 
         [0082]      FIG. 7A  is a perspective view of a still additional motor driver according to the first embodiment of the present invention, and  FIG. 7B  is a side view of the motor driver illustrated in  FIG. 7A . As illustrated in  FIGS. 7A and 7B , a protrusion  52   b  and a groove  51   b  each extending in an oblique direction are formed on/in the outer surface of each of the two side plates  23  and  24  of the housing  20 , the side plates  23  and  24  facing each other. Each of the side plates  23  and  24 , where the protrusion  52   b  and the groove  51   b  are formed, is parallel with the intersection line  21   d.    
         [0083]    As can be seen from  FIGS. 7A and 7B , each of the protrusion  52   b  and the groove  51   b  extends from one side-edge portion to the other side-edge portion of the outer surface of the corresponding one of the side plates  23  and  24 . In the example illustrated in  FIGS. 7A and 7B , the protrusion  52   b  and the groove  51   b  extend in parallel with each other. However, the protrusion  52   b  and the groove  51   b  need not be in parallel with each other as long as each extends in an oblique direction. 
         [0084]    In this configuration, cutting fluid dropping down to the motor driver  10  is guided to the outer surfaces of the side plates  23  and  24  of the housing  20 , along the inclined surfaces  21   a . The cutting fluid thus guided is further guided to the side-edge portions of the outer surfaces of the side plates  23  and  24  by the protrusions  52   b  and/or the grooves  51   b . With this configuration, it is apparent that the cutting fluid is collected at predetermined areas of the above-described side-edge portions, and consequently prevented from dropping down to other electronic components positioned in a lower part of the motor driver  10 . 
         [0085]      FIG. 8A  is a perspective view of a motor driver according to a second embodiment of the present invention, and  FIG. 8B  is a side view of the motor driver illustrated in  FIG. 8A . In  FIG. 8A  and some other drawings, a plurality of through-holes  28  are formed in the top plate  21  of the housing  20 . As can be seen from  FIG. 8B  and some other drawings, the fan motor  30  attached to the printed circuit board  35  is positioned below the through-holes  28 . In other words, in the second embodiment, the fan motor  30  is arranged with a distance from the inner surface  21   b  of the top plate  21  of the housing  20 . 
         [0086]    In  FIGS. 8A and 8B , the inner surface of the top plate  21  of the housing  20  is configured by two inclined surfaces  21   b . As illustrated in  FIG. 8B , each of the inclined surfaces  21   b  is inclined upward toward the center of the housing  20 . Accordingly, a line  21   d  of intersection of the inclined surfaces  21   b , which extends parallel with side plates  23  and  24  of the housing  20 , is in a higher position than edge portions of the inner surface of the top plate  21 . 
         [0087]    Moreover,  FIG. 8C  is a schematic side view of part of the motor driver illustrated in  FIG. 8A . When the fan motor  30  is in operation, cutting fluid mist is sprayed onto the inner surface  21   b  of the top plate  21 , as indicated by a white arrow in  FIG. 8C , and then accumulated as a fluid pool  39 . When the fluid pool  39  reaches a certain volume, the cutting fluid drops down under its own weight as indicated by solid-line arrows. 
         [0088]    In some examples of the second embodiment, the inclined surfaces  21   b  are used as the inner surface of the top plate  21 . Accordingly, the cutting fluid sprayed onto the inner surface of the top plate  21  of the motor driver  10  is guided to inner surfaces  23   b  and  24   b  of the side plates  23  and  24  of the housing  20 , along the inclined surfaces  21   b . With this configuration, the cutting fluid does not adhere to the electronic components  36  in the motor driver  10 . Hence, this configuration can prevent a breakdown of the electronic components  36  in the motor driver  10 , due to the cutting fluid. 
         [0089]      FIG. 9A  is a perspective view of another motor driver according to the second embodiment of the present invention, and  FIG. 9B  is a side view of the motor driver illustrated in  FIG. 9A . In  FIGS. 9A and 9B , each of two inclined surfaces  21   b  constituting the inner surface of the top plate  21  of the housing  20  is inclined downward toward the center of the housing  20 . Accordingly, the line  21   d  of intersection of the inclined surfaces  21   b , which extends in parallel with the side plates  23  and  24  of the housing  20 , is in a lower position than the edge portions of the inner surface of the top plate  21 . 
         [0090]    In this configuration, cutting fluid mist sprayed onto the inner surface  21   b  of the top plate  21  is guided to an area near the intersection line  21   d  on the top plate  21  of the housing  20 , along the inclined surfaces  21   b . Consequently, the cutting fluid is not collected near the inner surfaces  23   b  and  24   b  of the side plates  23  and  24  of the housing  20 , preventing the cutting fluid from adhering to the electronic components  36  positioned near the inner surfaces  23   b  and  24   b  of the side plates  23  and  24 . Thus, this configuration can prevent a breakdown of the electronic components  36  in the motor driver  10 , due to the cutting fluid. Naturally, the two inclined surfaces  21   b  may be designed to differ in size so that the intersection line  21   d  would be in a position apart from the electronic components  36 . 
         [0091]      FIG. 10A  is a perspective view of still another motor driver according to the second embodiment of the present invention, and  FIG. 10B  is a side view of the motor driver illustrated in  FIG. 10A . In  FIGS. 10A and 10B , the inner surface of the top plate  21  of the housing  20  is configured by a single inclined surface  21   b . As can be seen from  FIGS. 10A and 10B , an edge portion  21   e  of the single inclined surface  21   b  is in a higher position than an opposite edge portion  21   f  of the inclined surface  21   b.    
         [0092]    In this configuration, cutting fluid mist sprayed onto the inner surface  21   b  of the top plate  21  is guided to the inner surface  23   b  of the one side plate  23  of the housing  20  with respect to the top plate  21 , along the inclined surface  21   b . Consequently, the cutting fluid is prevented from adhering to the electronic components  36  in the housing  20 . Thus, it is apparent that this configuration can provide an effect similar to that described above. 
         [0093]      FIG. 11A  is a perspective view of a different motor driver according to the second embodiment of the present invention, and  FIG. 11B  is a side view of the motor driver illustrated in  FIG. 11A . As illustrated in  FIGS. 11A and 11B , a protrusion  52   b  and a groove  51   b  each extending in an oblique direction are formed on/in the inner surface of each of the two side plates  23  and  24  of the housing  20 , the two side plates  23  and  24  facing each other. The side plates  23  and  24 , where the protrusions  52   b  and the grooves  51   b  are formed, are in parallel with the intersection line  21   d.    
         [0094]    As can be seen from  FIGS. 11A and 11B , each of the protrusion  52   b  and the groove  51   b  extends from one side-edge portion to the other side-edge portion of the inner surface of the corresponding one of the side plates  23  and  24 . In the example illustrated in  FIGS. 11A and 11B , the protrusion  52   b  and the groove  51   b  extend in parallel with each other. However, the protrusion  52   b  and the groove  51   b  need not be in parallel with each other, as long as each extend in an oblique direction. 
         [0095]    In this configuration, cutting fluid sprayed onto the inner surface  21   b  of the top plate  21  is guided to the inner surfaces  23   b  and  24   b  of the side plates  23  and  24  of the housing  20 , along the inclined surfaces  21   b . The cutting fluid thus guided is further guided to the side-edge portions of the inner surfaces  23   b  and  24   b  of the side plates  23  and  24  by the protrusions  52   b  and/or the grooves  51   b . With this configuration, it is apparent that the cutting fluid is collected at predetermined areas of the above-described side-edge portions, and consequently prevented from dropping down to other electronic components positioned in a lower part of the motor driver  10 . 
         [0096]      FIG. 12A  is a perspective view of a cabinet according to the present invention, and  FIG. 12B  is a side view of the cabinet illustrated in  FIG. 12A . As illustrated in  FIGS. 12A and 12B , a cabinet  10 ′ is provided with electronic equipment  61  including electronic components for driving or controlling a motor for a machine tool or an industrial robot, and a radiator  62 , such as a heat sink. The cabinet  10 ′ includes a first wall  45  extending vertically. The electronic equipment  61  is attached to one surface of the first wall  45 , and the radiator  62  is attached to the other surface of the first wall  45 . In a precise sense, an opening (not illustrated) is formed in the first wall  45 , and the radiator  62  is attached directly to the electronic equipment  61  through the opening of the first wall  45 . Note that the cabinet  10 ′ may include only the electronic equipment  61 , or may include a combination of the electronic equipment  61  and one or more of the radiator  62 , a first fan motor  31 , and a second fan motor  32 . 
         [0097]    In some cases, the first fan motor  31  is attached to an upper end of the electronic equipment  61 , and the second fan motor  32  is attached to an upper end of the radiator  62 . The first fan motor  31  and the second fan motor  32  have a function of appropriately discharging heat from the electronic equipment  61  and the radiator  62 , respectively. 
         [0098]    Moreover, as illustrated in  FIGS. 12A ,  12   b , and  12 C, a second wall  46  extending laterally with respect to the first wall  45  is attached to an upper end of the first wall  45 . In  FIGS. 12A ,  12 B, and  12 C, the second wall  46  is configured by two partial walls  46   a  and  46   b . The two partial walls  46   a  and  46   b  are inclined so as to abut on the first wall  45 . 
         [0099]      FIG. 12D  is a schematic view illustrating a case in which the cabinet  10 ′ is configured by the electronic equipment  61  and the first fan motor  31 . As illustrated in  FIG. 12D , the second wall  46  may be configured only by a single partial wall  46   a.    
         [0100]      FIG. 13A  is a schematic side view of part of another cabinet according to the present invention. Moreover,  FIG. 13B  is a perspective view of the cabinet illustrated in  FIG. 13A , and  FIG. 13C  is a side view of the cabinet illustrated in  FIG. 13A . In  FIGS. 13A to 13C , a second wall  46  is flat and extends horizontally. To a bottom surface of the second wall  46 , a bulge  46   c  having a substantially triangular cross section is attached. As illustrated in  FIGS. 13A to 13C , it is assumed that a first wall  45  is attached to a tip of the bulge  46   c.    
         [0101]    The bulge  46   c  has a function similar to that of the inner surfaces of the partial walls  46   a  and  46   b  illustrated in  FIGS. 12A and 12B . As can be seen from  FIG. 13B , it is preferable that the width of the bulge  46   c  in a direction of a line of intersection of the first wall  45  and the second wall  46  be greater than the width of each of the first fan motor  31  and the second fan motor  32  in the above-described direction of the intersection line. 
         [0102]    When the first fan motor  31  and the second fan motor  32  are in operation, cutting fluid mist comes into each of the electronic equipment  61  and the radiator  62 , and is then discharged from the electronic equipment  61  and the radiator  62 , as indicated by white arrows in  FIG. 13A . The cutting fluid mist thus discharged is sprayed onto the second wall  46 , and accumulated as fluid pools  39 . When each of the fluid pools  39  reaches a certain volume, the cutting fluid drops down under its own weight. 
         [0103]    In  FIGS. 12A to 12C  and  FIGS. 13A to 13C , the second wall  46  is configured by the two partial walls  46   a  and  46   b  each inclined downward, or is provided with the bulge  46   c  on the one surface. With these configurations, the cutting fluid is guided to the one surface  45   a  and the other surface  45   b  of the first wall  45 , along the two partial walls  46   a  and  46   b  or the bulge  46   c . Accordingly, the cutting fluid does not adhere to the electronic equipment  61  of the cabinet  10 ′, preventing a breakdown of the electronic equipment  61  of the cabinet  10 ′, due to the cutting fluid. 
         [0104]      FIG. 14A  is a perspective view of another cabinet according to the present invention, and  FIG. 14B  is a back view of the cabinet illustrated in  FIG. 14A . In  FIGS. 14A and 14B , inverted V-shaped protrusions  47   a  and  47   b  are attached to respective surfaces of the first wall  45 . As illustrated in  FIGS. 14A and 14B , the inverted V-shaped protrusion  47   a  is positioned between the first fan motor  31  and the partial wall  46   a , while the inverted V-shaped protrusion  47   b  is positioned between the second fan motor  32  and the partial wall  46   b.    
         [0105]    As can be seen from  FIGS. 14A and 14B , the vertex of each of the inverted V-shaped protrusions  47   a  and  47   b  is positioned above the corresponding one of the first fan motor  31  and the second fan motor  32 . Consequently, cutting fluid guided to the first wall  45  along the partial walls  46   a  and  46   b  or the bulge  46   c  is further guided by the inverted V-shaped protrusions  47   a  and  47   b  away from the electronic equipment  61  and the radiator  62 . This configuration can further prevent the cutting fluid from adhering to the electronic equipment  61  and the radiator  62 . In addition, the cutting fluid is guided to predetermined areas, preventing the cutting fluid from dropping down to other electronic components. To provide this effect, it is preferable that the length of each of the inverted V-shaped protrusions  47   a  and  47   b  in the direction of the line of intersection of the first wall  45  and the second wall  46  be greater than the length of each of the electronic equipment  61  and the radiator  62  in the above-described direction of the intersection line. 
         [0106]      FIG. 15A  is a perspective view of still another cabinet according to the present invention, and  FIG. 15B  is a back view of the cabinet illustrated in  FIG. 15A . In  FIGS. 15A and 15B , elongated protrusions  48   a  and  48   b  are attached to the respective surfaces of the first wall  45 . As illustrated in  FIGS. 15A and 15B , the elongated protrusion  48   a  is positioned between the first fan motor  31  and the partial wall  46   a , while the elongated protrusion  48   b  is positioned between the second fan motor  32  and the partial wall  46   b.    
         [0107]    The cutting fluid guided to the first wall  45  along the partial walls  46   a  and  46   b  or the bulge  46   c  is further guided by the elongated protrusions  48   a  and  48   b  so as to be away from the electronic equipment  61  and the radiator  62 . This configuration can further prevent the cutting fluid from adhering to the electronic equipment  61  and the radiator  62 . In addition, the cutting fluid is guided to predetermined areas, preventing the cutting fluid from dropping to other electronic components. To provide this effect, it is preferable that the length of each of the elongated protrusions  48   a  and  48   b  in the direction of the line of intersection of the first wall  45  and the second wall  46  be greater than the length of each of the electronic equipment  61  and the radiator  62  in the above-described direction of the intersection line. 
         [0108]      FIG. 16A  is a perspective view of a different cabinet according to the present invention, and  FIG. 16B  is a side view of the cabinet illustrated in  FIG. 16A . In  FIGS. 16A and 16B , receiving parts  49   a  and  49   b  each having a substantially U-shaped cross section are attached to the respective surfaces of the first wall  45 . As illustrated in  FIGS. 16A and 16B , the receiving part  49   a  is positioned between the first fan motor  31  and the partial wall  46   a , while the receiving part  49   b  is positioned between the second fan motor  32  and the partial wall  46   b.    
         [0109]    The cutting fluid guided to the first wall  45  along the partial walls  46   a  and  46   b  or the bulge  46   c  is received by the receiving parts  49   a  and  49   b . With this configuration, the cutting fluid is prevented from adhering to the electronic equipment  61  and the radiator  62 , further preventing a breakdown of the electronic equipment  61 . To provide this effect, it is preferable that the length of each of the receiving parts  49   a  and  49   b  in the direction of the line of intersection of the first wall  45  and the second wall  46  be greater than the length of each of the electronic equipment  61  and the radiator  62  in the above-described direction of the intersection line. 
         [0110]    In addition, it is preferable that the cutting fluid accumulated in the receiving parts  49   a  and  49   b  be discharged from the receiving parts  49   a  and  49   b  regularly. For this reason, the receiving parts  49   a  and  49   b  may be inclined as the elongated protrusions  48   a  and  48   b . Note that appropriately combining the examples described above is within the scope of the invention. 
       Effect of the Invention 
       [0111]    In the first to sixth aspects, the outer surface of the top plate is configured by an inclined surface or inclined surfaces. Accordingly, even if cutting fluid sprayed onto the wall positioned above the motor driver drops down to the motor driver, the cutting fluid is guided to the outer surfaces of the side plates of the housing, along the inclined surface(s). As a result, the cutting fluid does not flow into the motor driver, preventing a breakdown of the electronic components in the motor driver, due to the cutting fluid. 
         [0112]    In the seventh to eleventh aspects, the inner surface of the top plate is configured by an inclined surface or inclined surfaces. Accordingly, cutting fluid sprayed onto the inner surface of the top plate of the motor driver is guided to the inner surfaces of the side plates of the housing, along the inclined surface(s). As a result, the cutting fluid does not adhere to the electronic components in the motor driver, preventing a breakdown of the electronic components in the motor driver, due to the cutting fluid. 
         [0113]    In the twelfth to fifteenth aspects, a bulge is provided to the one surface of the second wall. Accordingly, the cutting fluid sprayed onto the one surface of the second wall is guided to the first wall, along the bulge. As a result, the cutting fluid does not drop down to the electronic components, preventing a breakdown of the electronic components mounted on the cabinet, due to the cutting fluid. 
         [0114]    The present invention has been described above on the basis of the representative embodiments. However, it should be apparent to those skilled in the art that the above-described modifications as well as various other modifications, omissions, and additions can be made without departing from the spirit of the present invention.