Patent Abstract:
Electronic equipment installed outdoors to house an internal unit is provided, meeting the waterproof standard and having an easily replaceable structure of the internal unit. The electronic equipment has an enclosure having a cover and a case with an opening and an air vent, and an internal unit in which an electronic component is mounted. The internal unit has a heat sink and radiation fins for releasing heat generated by the electronic component. The fins are inserted into the opening. The heat sink has a draining portion formed below the fins in a direction perpendicular to an extending direction of the radiation fins, a groove for waterproofing around the fins except an upper portion thereof, and two protrusions for fitting above the fins. The case has a rib for waterproofing around the opening except an upper portion thereof, and two holes for fitting above the opening.

Full Description:
This is a continuation-in-part of application Ser. No. 12/022,189, filed on Jan. 30, 2008, now U.S. Pat. No. 7,782,618, the content of which is hereby incorporated by reference into this application. 
     CLAIM OF PRIORITY 
     The present application claims priority from Japanese patent application serial no. 2008-263036, filed on Oct. 9, 2008, the content of which is hereby incorporated by reference into this application. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to electronic equipment, and more particularly to electronic equipment installed outdoors. 
     Outdoor equipment enclosures for North America must successfully complete the standards of North America. Particularly, it is necessary to pass the following three tests relating to waterproofing, which are described in “Generic Requirements for Electronic Equipment Cabinets”, Telcordia Technologies, March 2000, GR-487-CORE issue 2, Section 3.28. Incidentally, Wind Driven Rain test is the most severe of the three tests. 
     1. Wind Driven Rain Test 
     After water spraying on the front surface, right surface, and left surface of an enclosure for 30 minutes each with a rainfall intensity of 150 mm/hr and a wind speed of 31 m/sec, the amount of water penetrating into the enclosure shall not exceed 1 cm^3 (cm 3 ) (1 gram of water) per 0.028 m^3 (m 3 ) (1 ft^3 (ft 3 )). 
     2. Rain Intrusion Test 
     Water droplets accumulated in the surface grooves and the door frame shall not enter the enclosure immediately after heavy rain. After water spraying on the front surface and the two side surfaces for 15 minutes each, the amount of water penetrating into the enclosure shall not exceed 1 cm^3 (cm 3 ) (1 gram of water) per 0.028 m^3 (m 3 ) (1 ft^3 (ft 3 )). 
     3. Lawn Sprinklers Test 
     After simulation of sprinkler water spraying at a downward angle of 45 degrees on the front surface and the two side surfaces for 15 minutes or 45 minutes in total, the amount of water penetrating into the enclosure shall not exceed 1 cm^3 (cm 3 ) (1 gram of water) per 0.028 m^3 (m 3 ) (1 ft^3 (ft 3 )). 
     In addition to the waterproof standard described above, the outdoor equipment enclosure for North America should meet the requirement that an electronic component housed therein can easily be replaced. In other words, the enclosure should have a structure capable of replacing an internal unit including an electronic component within the enclosure, instead of replacing the whole equipment, for the maintenance and replacement of the equipment. This is also the specification that allows the installation of the enclosure first and then the installation of the internal unit afterwards. 
     Further, from the point of view of the cost and weight, the material of the enclosure is preferably resin. However, it is difficult for a resin seal enclosure to fully achieve radiation performance. Hence, it is necessary to ensure the radiation performance by providing an opening in the resin enclosure through which a radiation fin of a heat sink thermally connected to the electronic component, is partially exposed to the outside of the resin enclosure. Here, the heat fin may be splashed with water, but the water penetration into portions other than the radiation fin is not allowed. 
     Further, in general, the electronic component and the heat sink are connected by a thermally conducted sheet. This makes it difficult to remove only a board in which the electronic component is mounted in the maintenance and replacement of the electronic component. Thus, the replacement of the electronic component should be done by removing the electronic component together with the heat sink. The unit of replacement is called an internal unit. 
     US 2009/0059534 discloses electronic equipment that can facilitate heat conduction from the inside to the outside of an enclosure in which an internal unit can be replaced. The enclosure structure of the electronic equipment is provided with a heat sink for releasing the inside heat. The heat sink has a heat radiation surface exposed from the bottom of the enclosure to increase the efficiency of releasing the heat from the inside to the outside of the enclosure. A canopy structure is provided below the radiation fin in order to prevent water from entering into the enclosure. In addition to the canopy structure, the electronic equipment has a structure in which a rib formed around the entire periphery of the opening for the heat sink of the case is fitted into a groove formed around the entire periphery of the heat sink, sufficiently providing the waterproof performance without using packing between the case and the heat sink. However, this structure requires eight screws to mount the internal unit. Thus, the replacement of the internal unit should be done by removing all the eight screws and tightening them again. Further, the internal unit is not fixed to the case without the screws tightened, and is likely to fall down in the replacement operation. Thus, the replacement performance is not good. 
     SUMMARY OF THE INVENTION 
     A proposed measure to prevent falling down of the internal unit in the replacement operation will be described with reference to  FIGS. 1A and 1B . Here,  FIG. 1A  is a cross sectional view taken along line A-A of  FIG. 5  of an embodiment described later. In the figure, a unit cover  510  is omitted for simplicity, and a hole  104  of the case  10  is viewed in across section taken along line B-B of  FIG. 5 .  FIG. 1B  is an enlarged view of a portion C in  FIG. 1A . As is apparent from  FIGS. 1A and 1B , which show the proposed measure to prevent falling down of the internal unit, the hole  104  of the case  10  and a protrusion  532  of the heat sink  530  are fitted together to prevent the internal unit  40  from falling down rotating about the y axis. In the portion C, however, a first groove  533  and a second groove  534  exist in the y axis of a radiation fin  540  of the heat sink  530 . A first rib  101  and a second rib  102  exist above an opening  130  of the cover  10 . In such a case, the protrusion  532  is not inserted into the hole  104 , so that the case  10  and the heat sink  530  are not fitted together. 
     The present invention provides electronic equipment meeting the waterproof standard of North America for outdoor installation with a replaceable internal unit including an electronic component. 
     Further, the present invention provides electronic equipment meeting the waterproof standard of North America for outdoor installation with a replaceable internal unit including an electronic component, in which the internal unit can easily be replaced. 
     The present invention solves the above problems by providing electronic equipment including an enclosure having a case with an opening formed therein and a cover, and an internal unit in which an electronic component is mounted. The internal unit has a heat sink for absorbing heat generated by the electronic component, plural radiation fins formed in the heat sink to release the heat from the heat sink, and a draining portion formed below the radiation fins of the heat sink in a direction perpendicular to an extending direction of the radiation fins. The radiation fins of the internal unit are inserted into the opening of the case of the enclosure. The case has a rib arranged in a horseshoe shape around the opening except an upper portion thereof. The heat sink has a groove formed around the radiation fins except an upper portion thereof so as to receive the rib. The electronic equipment further includes: protrusions for falling-down prevention in the upper portion of the inside of the heat sink, in order to prevent the internal unit from falling down rotating forward about the bottom side of the internal unit, when the internal unit connected to the heat sink is connected to the enclosure (case) in a plane including the vertical direction; and holes into which the protrusions of the heat sink mounted to the case are fitted. The rib is formed in the three sides of the opening except the upper side thereof for the heat sink of the case. The groove is formed in the three sides of the heat sink except the upper side thereof. The rib and the groove are fitted together. 
     According to the present invention, it is possible to provide electronic equipment meeting the waterproof standard of North America for outdoor installation with a replaceable internal unit including an electronic component. Further, according to the present invention, it is possible to provide electronic equipment meeting the waterproof standard of North America for outdoor installation with a replaceable internal unit including an electronic component, in which the internal unit can easily be replaced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are cross-sectional views of a key assembly, showing a measure for preventing falling down of an internal unit of electronic equipment; 
         FIG. 2  is a perspective view showing a state in which an enclosure is attached to an outdoor wall surface; 
         FIG. 3  is a perspective view of the back side of the enclosure; 
         FIG. 4  is a perspective view of a state in which a cover of the electronic equipment is open; 
         FIG. 5  is a front view of a case of the enclosure; 
         FIG. 6  is a front view of a heat sink on the side of radiation fins; 
         FIG. 7  is a cross-sectional view of the electronic equipment to be assembled; 
         FIG. 8  is a cross-sectional view of the electronic equipment; 
         FIGS. 9A and 9B  are a cross-sectional view and an enlarged view, respectively, of a portion of a canopy structure; 
         FIGS. 10A and 10B  are a cross-sectional view and an enlarged view, respectively, of a fitting portion between a protrusion and a hole; and 
         FIGS. 11A and 11B  are a cross-sectional view and an enlarged view, respectively, of a portion of a gap between the upper heat sink and the case. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, a preferred embodiment will be described using examples with reference to the accompanying drawings. Identical or similar components are denoted by the same reference numerals throughout the drawings and the description will not be repeated. Here,  FIG. 2  is a perspective view showing a state in which an enclosure is attached to an outdoor wall surface.  FIG. 3  is a perspective view of the back side of the enclosure.  FIG. 4  is a perspective view showing a state in which a cover of the enclosure of the electronic equipment is open.  FIG. 5  is a front view of a case of the enclosure.  FIG. 6  is a front view of a heat sink on the side of radiation fins.  FIG. 7  is a cross-sectional view of the electronic equipment to be assembled.  FIG. 8  is a cross-sectional view of the electronic equipment.  FIGS. 9A and 9B  are a cross-sectional view and an enlarged view, respectively, of a canopy portion.  FIGS. 10A and 10B  are a cross-sectional view and an enlarged view, respectively, of a portion of a gap between a protrusion and a hole.  FIGS. 11A and 11B  are a cross-sectional view and an enlarged view, respectively, of the portion of the gap between the upper heat sink and the case, as seen from another direction. 
     In  FIG. 2 , an outdoor enclosure  1  including a case  10  and a cover  20  is fixed to a wall  70 . The cover  10  and the case  20  are both made of resin. Further, as shown in  FIG. 3 , the case  10  includes a lower air vent  110  and an upper air vent  120  for cooling streams. An internal unit  40  to be mounted can be mounted to the outdoor enclosure fixed to a wall surface  70 . Incidentally, the lower air vent  110  is not shown in  FIG. 3  due to perspective viewing, but it is explicitly shown in  FIG. 9B  described later. In addition, a mounting hole to the wall surface  70  is omitted in  FIGS. 3 and 5  described later. 
       FIG. 4  shows electronic equipment  1000  with the cover  20  open. The electronic equipment  1000  is in a state in which the internal unit  40  is connected to the outdoor enclosure  1 . In  FIG. 4 , the cover  20  and the case  10  are connected by hinges  30 . However, it is also possible that the cover  20  is removable and fixed to the case  10  by screws. The cover  20  and the case  10  are resin sealed, making it possible to easily realize a water seal structure. 
     The case  10  will be described with reference to  FIG. 5 . In  FIG. 5 , the maximum profile of the case  10  is substantially square with 303×296 mm sides. The case  10  has frame-side hinge portions  31  on the left side surface, and an opening  130  of 122×212 mm in a central portion thereof. In the case  10 , a first rib  101  and a second rib  102  are provided around the opening  130  except the upper side thereof. Two screw holes  103  are provided below the opening  130  of the case in order to fix the internal unit  40 . There are also two holes  104  formed in a downward direction in the x-y plane above the opening  130  of the case  10  in order to fit the internal unit  40  and the case  10  together. Further, the case  10  has two ribs  105  to receive the internal unit  40  in the z-axis direction. 
     A heat sink  530  will be described with reference to  FIG. 6 . In  FIG. 6 , the maximum profile of the heat sink  530  is 179.5×265 mm. The heat sink  530  has radiation fins  540 , and a canopy  531  below the radiation fins  540 . There are two holes  535  provided further below the canopy  531  in order to fix the internal unit  40 . The canopy  531  separates water droplets flowing through the radiation fins  540 , from a vertical planar portion of the body of the heat sink  530 . Further, the heat sink  530  has a first groove  533  and a second groove  534  around the radiation fins  540  except the upper side thereof. Incidentally, the first groove  533  and the second groove  534  reach beyond the heat sink  530  in the z-axis direction. The heat sink  530  has protrusions  532  to be used for fitting the internal unit  40  at the both ends of the upper portion of the heat sink  530 . 
     The components of the electronic equipment  1000  will be described with reference to  FIG. 7 . Here,  FIG. 7  is a cross-sectional view taken along line A-A of  FIG. 5 . In  FIG. 7 , the electronic equipment  1000  is configured such that the internal unit  40  is mounted to the case  10  and then covered with the cover  20 . 
     The internal unit  40  includes the heat sink  530 , a thermally conductive sheet  550 , an electronic component  560 , a board  520 , a unit cover  510 , and board fixing screws  570 . The electronic component  560  is mounted on the board  520 , in which heat is transmitted to the heat sink  530  through the thermally conductive sheet  550 . The heat sink  530  releases the heat from the radiation fins  540  to the atmosphere outside the enclosure. The internal unit  40  is fixed to the case  10  by using two internal unit fixing screws  580 . Incidentally, the case  10  is illustrated with the side views of the hole  104  and the rib  105  that have been described with reference to  FIG. 5 . 
     The cross sectional structure of the assembled electronic equipment  1000  will be described with reference to  FIG. 8 . Here,  FIG. 8  is also a cross-sectional view taken along line A-A of  FIG. 5 . The unit cover  510  is omitted for simplicity, and the hole  104  of the case  10  is viewed in a cross section taken along line B-B of  FIG. 5 . In  FIG. 8 , air entering from the lower air vent  110  of the case  10  flows upward while taking the heat out of the radiation fins  540 . Then, the air flows out of the upper air vent  120 . As shown in  FIG. 5 , the case  10  has the opening  130  into which the radiation fins  540  are inserted to cool the heated air brought into contact with external air entering from the lower air vent  110 . The size of the opening  130  is determined depending on the size of the radiation fins  540  to be exposed therefrom. The size of the radiation fins  540  is determined based on the results of a thermal simulation and a temperature test. 
     When the internal unit  40  is mounted to the case  10 , the protrusions  532  provided above the heat sink  530  are first inserted into the holes  104  of the case  10  all the way to the bottom. Next, the radiation fins  540  are inserted into the opening  130  of the case  10 . In this structure, because the rib  105  of the case  10  receives the lower end surface of the heat sink  530 , the internal unit  40  is prevented from falling down to the lower side. Further, because the protrusions  532  are inserted into the holes  104  of the case  10 , the internal unit  40  is also prevented from falling down to the front side. For this reason, it is possible to mount the internal unit  40  to the case  10  without worrying about the internal unit  40  falling down, even in a state in which the internal unit  40  is not tightened with the screws in the replacement operation. 
     The mechanism to withstand the waterproof test will be described with reference to  FIGS. 9A and 9B . Here,  FIG. 9A  is a cross-sectional view taken along line A-A of  FIG. 5 .  FIG. 9B  is an enlarged view of a portion E of  FIG. 9A . In  FIGS. 9A and 9B , water entering from the upper air vent  120  in a waterproof test flows downward through the heat sink  530 . However, the canopy  531  serves as a draining portion, preventing the water from flowing into the gap  60  between the lower heat sink and the case. This makes it possible to prevent almost all the water from flowing into the gap between the lower heat sink and the case. For the case in which a little water flows into the gap, narrow spaces are provided in the fitting portions respectively between the first groove  533  and the second groove  534  in the heat sink  530 , and the first rib  101  and the second rib  102  in the case  10 . This ensures that the water is kept in the narrow spaces by its surface tension without entering into the enclosure. 
     Next, the water flow in the vicinity of the upper air vent  120  will be described with reference to  FIGS. 10A and 10B  as well as  FIGS. 11A and 11B . Here,  FIG. 10A  is a cross-sectional view taken along line A-A of  FIG. 5 . The unit cover  510  is omitted for simplicity, and the hole  104  is viewed in a cross-section taken along line B-B of  FIG. 5 .  FIG. 10B  is an enlarged view of a portion F of  FIG. 10A . Further,  FIG. 11A  is a cross-sectional view taken along line G-G of  FIG. 5 .  FIG. 11B  is an enlarged view of a portion H of  FIG. 11A . 
     In  FIGS. 10A and 10B , when water entering from the upper air vent  120  reaches a gap  61  between the upper heat sink and the case, the water is pumped up by the capillary action. Then, the pumped up water spreads over the area in which the capillary tube is formed. For this reason, in  FIGS. 11A and 11B , the water spreads in the longitudinal direction along the gap  61  between the upper heat sink and the case, and reaches the first groove  533 . The first groove  533  has a tiny space in which no capillary phenomenon occurs, preventing the water from spreading in the longitudinal direction across the first groove  533 . The water stays in the first groove  533  due to its surface tension, or flows downward along the first groove  533 . Even if the water flows across the first groove  533 , the water stays in the second groove  534  due to its surface tension or flows downward along the second groove  534  in a similar manner. This ensures that the water does not enter into the enclosure. As described above, in order to prevent the water pumped up by the capillary phenomenon from entering into the enclosure, it is preferable that the first groove  533  and the second groove  534  are formed to reach the upper end surface of the heat sink  530 . 
     If the grooves do not reach the upper end surface of the heat sink  530  and if the grooves end 10 mm from the upper end surface thereof, the portion in which the grooves are not formed might become a path through which the water flows. The first groove  533  and the second groove  534  interrupt such a water flow path. Thus, it is preferable that the first groove  533  and the second groove  534  are formed to reach the upper end surface of the heat sink  530 . 
     The electronic equipment according to the above described embodiment has passed the waterproof test of IPX5 of International Standard IEC/EN60529 (JIS C0920). The inventors&#39; experience shows that the electronic equipment having passed the waterproof test of IPX5 will also pass the Wind Driven Rain test without problems. 
     According to the above described embodiment, the internal unit can easily be joined to the enclosure temporarily. Further, the number of screws can be reduced from 8 to 2. As a result, the workability in installing/replacing the internal unit is good.

Technology Classification (CPC): 7