Abstract:
There is provided an electronic apparatus that is free of the problems with the prior art and is capable of achieving higher efficiency of cooling the interior of the casing without sacrificing cost reduction and designing compact in size. A casing houses a plurality of circuit boards having electronic parts mounted thereon and at least one high load part that generates heat. The casing has exhaust ports formed therein for heat radiation and exhaust ports for heat radiation. The plurality of circuit boards are comprised of a first circuit board and a second circuit board. The first circuit board is disposed to extend substantially horizontally, and the second circuit board is disposed to extend substantially vertically with a horizontal gap provided between the first circuit board and the second circuit board. The at least one high load part is arranged below the horizontal gap, and the exhaust ports are arranged above the horizontal gap.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an electronic apparatus, and more specifically, to an electronic apparatus having circuit boards and high load parts that generate heat, arranged in a casing. 
   2. Description of the Related Art 
   With recent electronic apparatuses becoming multifunctionized and more compact in size, there is a general tendency that a plurality of circuit boards, a power source, and expansion cards are packed into a casing of an electronic apparatus having a limited space. In such an electronic apparatus, hot air generated by the power source or electronic parts is blocked by, for example, a plurality of circuit boards which are closely stacked one upon another, to be confined within the casing, so that the electronic parts in the casing become excessively hot. This poses a problem that some electronic parts malfunction or become defective and hence cannot maintain their required performance. 
   To avoid this problem, as means for discharging heat generated in the casing to the outside of the electronic apparatus, a fan or a heat sink has been provided in the casing. However, multifunctionalization and speedup of electronic apparatuses increase the amount of heat generated in the electronic parts. This leads to increased cases where the fan or heat sink is insufficient to ventilate the interior of the casing in which the plurality of circuit boards and electronic parts are clustered. Thus, there is demand for a cooling structure for the electronic apparatus which can achieve high cooling efficiency. 
   For example, Japanese Laid-Open Patent Publication (Kokai) No. 2000-049482 discloses a cooling structure for electronic apparatuses which is comprised of a plurality of fans that blow uniform air flows between a plurality of circuit boards mounted in stages in the casing, and guide vanes that guide the uniform air flows. 
   However, with the disclosed cooling structure for electronic apparatuses, fans are provided between adjacent circuit boards, and therefore, the following problems arise: 1) The number of fans increases; 2) Costs increase; 3) The size of the casing increases; and 4) The fan themselves generate increased heat and noise. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an electronic apparatus that is free of the problems with the prior art and is capable of achieving higher efficiency of cooling the interior of the casing without sacrificing cost reduction and designing compact in size. 
   To attain the above object, in a first aspect of the present invention, there is provided an electronic apparatus comprising a plurality of circuit boards having electronic parts mounted thereon, at least one high load part that generates heat, and a casing that houses the plurality of circuit boards and the at least one high load part and has exhaust ports formed therein for heat radiation, wherein the electronic apparatus is disposed to extend substantially horizontally, and the plurality of circuit boards comprise a first circuit board disposed to extend substantially horizontally and a second circuit board disposed to extend substantially vertically with a horizontal gap provided between the first circuit board and the second circuit board, the at least one high load part is arranged below the horizontal gap, and the exhaust ports are arranged above the horizontal gap. 
   According to the first aspect of the present invention, heat generated by high load parts, arranged below the horizontal gap between the first circuit board and the second circuit board, acts to heat the air surrounding these high load parts. Consequently, upward air flows are generated, which pass through the horizontal gap. The upward air flows are discharged through the exhaust ports disposed above the gap. Thus, the heat in the casing is discharged to the outside of the casing together with the upward air flows, and therefore the circuit boards and the high load parts can be effectively cooled, to thereby improve the cooling efficiency in the casing without sacrificing cost reduction and designing compact in size. 
   Moreover, no fan may be provided in the casing if the heat in the casing can be efficiently discharged to the outside of the casing. Even if any fans are used, fans can be used, which consume less power than conventional fans used for ventilating the interior of the casing. 
   Preferably, the casing comprises a slanted top panel, a front plate, a rear plate, a pair of side plates, and a bottom plate and has a generally wedge-like shape as viewed from a side thereof. 
   With this arrangement, heated air can be guided to the higher end of the casing due to the generally wedge-like shape of the casing, and the guided air can be discharged through the exhaust ports. As a result, the interior of the casing can be efficiently ventilated. Such a shape of the casing can be adopted as the side shape of a mixing apparatus, the side shape of the upper part of a cathode-ray tube television set, or the like. 
   More preferably, at least one of the first circuit board and second circuit board has mounted thereon electronic parts constituting an audio signal modulating circuit, and the at least one high load part is a power source or an expansion card. 
   With this arrangement, for example, even if the electronic apparatus is a mixing apparatus in which heat tends to accumulate in the casing, the heat generated by the high load parts such as the power source and the expansion card causes the upward air flows, and therefore the circuit boards and the high load parts can be effectively cooled. 
   Still more preferably, the exhaust ports are formed at higher locations of the slanted top panel. 
   With this arrangement, the heat in the casing can be efficiently discharged to the outside of the casing together with the upward air flows. 
   Preferably, the plurality of circuit boards include a third circuit board, and the casing comprises a panel shaft pivoted to an end of the slanted top panel corresponding to the front plate, the slanted top panel being capable of being pivotally moved about the panel shaft, a frame for having mounted thereon the third circuit board between the pair of side plates such that the third circuit board extends substantially horizontally, and a frame shaft pivoted to one end of the frame in a vicinity of a center of each of the pair of side plates, the frame being capable of being pivotally moved about the frame shaft in a direction in which the top panel is pivotally moved. 
   With this arrangement, the slanted top panel can be pivotally moved about the panel shaft and the frame can be pivotally moved about the frame shaft so that maintenance can be easily carried out. Moreover, the panel shaft is pivoted to an end of the slanted top panel corresponding to the front plate, and the frame shaft is pivoted to one end of the frame in the vicinity of the center of each of the pair of side plates, to thereby provide space in the vicinity of the pivoted part of the frame shaft. 
   As a result, air flows are easily generated in the casing, to thereby improve the cooling efficiency in the casing. 
   More preferably, the electronic apparatus further comprises a fourth circuit board having operating elements mounted thereon, and the slanted top panel has formed therein a plurality of holes and slots through which the operating elements penetrate to project outward of the slanted top panel. 
   With this arrangement, air can be discharged through the plurality of holes and slots formed in the slanted top panel. 
   Still more preferably, the plurality of circuit boards include a fifth circuit board, and the frame has mounted thereon the third circuit board on which electronic parts are mounted and the fifth circuit board on which other electronic parts are mounted, and the third circuit board and the fifth circuit board are disposed such that surfaces of the third circuit board and the fifth circuit board on which no electronic parts are mounted are opposed to each other. 
   With this arrangement, the electronic parts mounted on the third circuit board and other electronic parts mounted on the fifth circuit board can be easily exposed to air flows passing over the respective circuit boards, whereby improved cooling effects can be obtained to enable the electronic parts to stably exhibit their functions. 
   Still more preferably, the electronic apparatus is a mixing apparatus for audio signals. 
   With this arrangement, even if the electronic apparatus is a mixing apparatus in which heat tends to accumulate in the casing, the heat generated by the high load parts such as the power source and the expansion card causes the upward air flows, and therefore the circuit boards and the high load parts can be effectively cooled. 
   The above and other objects, features, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing the appearance of an electronic apparatus  100  according to a first embodiment of the present invention; 
       FIG. 2  is a side view of the electronic apparatus  100 , showing air flows generated inside the electronic apparatus  100  shown in  FIG. 1 ; 
       FIG. 3  is a side view of the electronic apparatus  100 , shown in  FIG. 1 , schematically showing a top panel  11  and a frame  40  which have been pivotally moved to a position for maintenance; 
       FIG. 4  is a plan view showing the arrangement of component parts inside the electronic apparatus, in which a second circuit board  22  and a third circuit board  23  are mounted on the frame  40 ; 
       FIG. 5  is a plan view showing the arrangement of a power source  31  and expansion slots  32   a  on a bottom plate  15 ; 
       FIG. 6  is a side view of an electronic apparatus  100   a  according to a second embodiment of the present invention, showing air flows generated inside the electronic apparatus  100   a ; and 
       FIG. 7  is a side view of an electronic apparatus  100   b  according to a third embodiment of the present invention, showing air flows generated inside the electronic apparatus  100   b.   
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention will now be described below in detail with reference to the drawings showing preferred embodiments thereof. 
     FIG. 1  is a perspective view showing the appearance of an electronic apparatus  100  according to a first embodiment of the present invention.  FIG. 2  is a side view of the electronic apparatus  100 , schematically showing air flows generated inside the electronic apparatus  100  shown in FIG.  1 . 
   As shown in  FIGS. 1 and 2 , a casing  10  of the electronic apparatus  100  according to the present invention is comprised of a top panel  11 , a front plate  12 , a rear plate  13 , a pair of side plates  14 , and a bottom plate  15 . The casing  10  has a generally wedge-like shape as viewed from a side thereof. 
   The top panel  11  is formed therein with a plurality of holes and slots through which operating elements such as faders, knobs, push buttons, and a display panel penetrate and project outward of the top panel  11 . To facilitate operations of the operating elements, the top panel  11  is slanted such that the rear plate  13  is higher in level than the front panel  12 . Exhaust ports  17  are formed in a rear end of the top panel  11 . Further, intake ports  16  are formed in the front panel  12 , and intake ports  16   a  are formed in a lower part of the rear plate  13 . 
   The electronic apparatus  100  according to the present embodiment is implemented as a mixing apparatus for audio signals. The casing  10  of the electronic apparatus  100  houses a first circuit board  21 , a second circuit board  22 , a third circuit board  23 , and a fourth circuit board  24 , on which electronic parts constituting audio signal modulating circuits or the like are mounted, as well as a power source  31  and an expansion card  32  as high load parts that generate heat. The expansion card  32  is inserted into an expansion slot  32   a . A program stored in a ROM in the expansion card  32  is transmitted to a predetermined circuit board via the expansion slot  32   a.    
   The first circuit board  21  and the third circuit board  23  are disposed to extend substantially horizontally. The second circuit  22  is disposed to extend substantially vertically at a location between the first circuit board  21  and the third circuit board  23  with a horizontal gap  80  provided from the third circuit board  23  and the first circuit board  21 , respectively. The fourth circuit board  24  is mounted on a back surface (inner surface) of the top panel  11  such that operating elements mounted on the fourth circuit board  24  penetrate through the holes and slots formed in the top panel  11  and project outward of the top panel  11 . A fifth circuit board  25  is mounted on a back surface of the third circuit board  23  such that their back surfaces (i.e. the surfaces on which no electronic parts are mounted) are opposed to each other. Thus, the electronic parts mounted on the fifth circuit board  25  and third circuit board  23  can be easily exposed to air flows passing over the respective circuit boards, whereby improved cooling effects can be obtained to enable the electronic parts to stably exhibit their functions. The power source  31  and the expansion card  32  are arranged on the bottom plate  15  at a location below the horizontal gap  80 . 
   The first circuit board  21  is fixed to the side plates  14  and bottom plate  15 , the third circuit board  23  and the fifth circuit board  25  to the side plates  14  via a frame  40 , and the fourth circuit board  24  to the top panel  11 , by respective fixing means, not shown. 
     FIG. 3  is a side view of the electronic apparatus  100 , shown in  FIG. 1 , schematically showing the top panel  11  and the frame  40  which have been pivotally moved to a position for maintenance. 
   A panel shaft  42  is pivoted to an end of the top panel  11  on the front panel  12  side, about which the top panel  11  is pivotally moved to be opened and closed. A frame shaft  41 , about which the frame  40  is vertically pivotally moved, is pivoted to a front end of the frame  40  corresponding to a front end of the third circuit board  23  at a longitudinally intermediate location in the casing  10  (in the vicinity of a longitudinal center of each of the side plates  14 ). 
   As shown in  FIG. 3 , the top panel  11  can be pivotally moved about the panel shaft  42  and the frame  40  can be pivotally moved about the frame shaft  41  so that maintenance can be easily carried out. The frame  40  constitutes a rear panel  130  as a part of the rear plate  13 . The second circuit board  22  is mounted on an inner surface of the rear panel  130 . 
     FIG. 4  is a plan view showing the arrangement of component parts inside the electronic apparatus, in which the second circuit board  22  and the third circuit board  23  are mounted on the frame  40 .  FIG. 5  is a plan view showing the arrangement of the power source  31  and the expansion slots  32   a  on the bottom plate  15 . 
   As shown in  FIG. 4 , the second circuit board  22  is provided with a plurality of input and output terminals  220  to which external audio apparatuses and electronic musical instruments are connected. The input and output terminals  220  are arranged at intervals in the horizontal direction and are connected to the second circuit board  22 . Alternatively to or in addition to the plurality of input and output terminals  220 , the third circuit board  22  may be provided with a plurality of switches or the like. 
   The opposite sides of the third circuit board  23  which are opposed to the pair of side plates  14  are fixed to the frame  40 . Further, input and output elements  230  such as switches are provided on the third circuit board  23 , which penetrate through openings formed in the top panel  11  and project outward of the top panel  11 . 
   With the above arrangement of the electronic apparatus  100  of the present embodiment, heat generated by the power source  31  and expansion card  32  as high load parts, arranged below the horizontal gap  80 , acts to heat the air surrounding these high load parts. Consequently, upward air flows are generated, which pass through the horizontal gap  80 . The upward air flows are discharged through the exhaust ports  17  disposed above the gap  80 . 
   This causes spontaneous generation of air flows entering the intake ports  16  and  16   a , then passing between the circuit boards  21  to  24 , between the circuit boards  21  to  24  and the casing  10 , and through the horizontal gap  80 , and finally reaching the exhaust ports  17 . As a result, the interior of the casing  10  can be efficiently ventilated to effectively cool the circuit boards  21  to  24 , the power source  31 , and the expansion card  32 . It should be noted that the arrangement of the circuit boards  21  to  24 , the power source  31 , and other component parts, as well as the manners of fixing or mounting them, may be freely set insofar as the above effects can be produced. 
   Furthermore, with the arrangement according to the present embodiment, air flows are generated, which pass between the plurality of input and output terminals  220  arranged at intervals, through a space  82  ( FIG. 2 ) located between the front plate  12  and the frame shaft  41  of the third circuit board  23 , and through gaps between the inner peripheries of the plurality of holes and slots in the top panel  11  and the outer peripheries of the input and output members  230 , to further enhance the effects of cooling of the interior of the casing. 
   To further improve the ventilation efficiency, with the arrangement according to the present embodiment, vertical air flows which are substantially straight in the vertical direction, extending from the power source  31  and expansion card  32 , which act as heat sources, through the horizontal gap  80  to the exhaust ports  17  are formed. Further, electronic parts such as ICs, which generate much heat, are arranged on the second circuit board  22  so that heat generated by these parts can be discharged directly through the vertical air flows. Furthermore, air heated while flowing along the first circuit board  21  and the third circuit board  23  is joined to the vertical air flows. 
   Thus, according to the electronic apparatus of the present embodiment, the interior of the casing  10  can be cooled even without using any fans as provided in the conventional electronic apparatus. This makes it possible to reduce the cost and space in the casing required to install fans and eliminate electric noise caused by fans or other noise. 
   The intake ports  16  and  16   a  and the exhaust ports  17  may be formed at locations different from those described above; they may be formed in the side plates  14 . However, the intake ports  16  and  16   a  should desirably be formed in a lower part of the casing  10 , as shown in FIG.  2 . This enables the creation of air flows upwardly extending from the lower part of the casing  10  to an upper part thereof, which are induced by the above described upward air flows. Particularly, according to the arrangement shown in  FIG. 2 , the intake ports  16  and  16   a  are arranged such that air introduced through the intake ports  16  and  16   a  causes air flows that come into contact with the high load parts. Consequently, the high load parts do not only discharge their own heat through the upward air flows but are also brought into contact with the air flows flowing in through the intake ports  16  and  16   a , so that the high load parts are cooled by outside air. 
   If the casing is designed such that appropriate gas are formed in the casing when assembled and/or component parts having openings through which outside air can flow in are used, a sufficient amount of air can flow in through the gaps and/or the openings, then the intake ports  16  and  16   a  can be omitted. For exhaust, air can be exhausted not only through the exhaust ports  17  but also through the plurality of holes in the top panel  11 , through which the operating portions are projected. 
   Further, since the exhaust ports  17  are formed at the rear panel  13  side end of the top panel  11 , i.e. at higher positions in the casing  10 , the heat in the casing can be efficiently discharged to the outside of the casing  10  together with the upward air flows. 
   Next, a second embodiment of the present invention will be described with reference to FIG.  6 .  FIG. 6  is a side view of an electronic apparatus  100   a  according to a second embodiment of the present invention, showing air flows generated inside the electronic apparatus  100   a.    
   The electronic apparatus  100   a  according to the second embodiment is distinguished from the electronic apparatus  100  of the first embodiment mainly in that a fan  50  is used and a second circuit board  22   a  is separated from the frame  40 . 
   In the electronic apparatus  100   a  according to the present embodiment, a casing  10   a  has exhaust ports  17   a  in its rear plate  13   a , and the fan  50  is provided in the casing  10   a . Further, in the present embodiment, the second circuit board  22   a  is separated from the frame  40  and fixed to the side plates  14  of the casing  10   a . Except for these, the arrangement of the present embodiment is almost the same as that of the above described first embodiment. 
   Also in the present embodiment, heat generated by the power source  31  and expansion card  32  acts to heat the air surrounding the power source  31  and expansion card  32  to generate upward air flows passing through the horizontal gap  80 . The upward air flows are discharged through the exhaust ports  17   a  arranged above the gap  80 . Further, in the present embodiment, the fan  50  creates negative pressure in a region of the interior of the casing  10   a  which corresponds to an upper part of the upper panel  11 . This stabilizes the upward air flows. 
   With the arrangement of the second embodiment, air flows are generated, which enter the intake ports  16  and  16   a , then pass between the circuit boards  21  and  22   a  and  24  and a circuit board  23   a , between each of the circuit boards  21 ,  22   a ,  23   a , and  24  and the casing  10 , and through the horizontal gap  80 , and finally are discharged through the exhaust ports  17   a . Consequently, the interior of the casing  10   a  can be efficiently ventilated to effectively cool the circuit boards  21 ,  22   a ,  23   a , and  24 , the power source  31 , and the expansion card  32 . 
   As the fan  50 , a fan providing output power that can just supplement a spontaneously generated upward air flows may be used. Therefore, the fan  50  may consume less power than conventional fans. Thus, noise can be suppressed to a lower value than the conventional arrangement using fans. 
   Next, a third embodiment of the present invention will be described with reference to FIG.  7 .  FIG. 7  is a side view of an electronic apparatus  100   b  according to the third embodiment showing air flows generated inside the electronic apparatus  100   b.    
   The electronic apparatus  100   b  according to the third embodiment is distinguished from the electronic apparatus  100   a  according to the second embodiment in that a second circuit board  22   b  is disposed to extend substantially parallel with the side plates  14 . 
   The present embodiment is intended to solve the problem that heat is generated by ICs and the like mounted on the circuit boards instead of the power source  31  and expansion card  32 , described above. Except for this, the electronic apparatus  100   b  is identical in construction with the electronic apparatus  100   a  shown in FIG.  5 . 
   In the present embodiment, ICs  33  as high load parts are mounted on the second circuit board  22   b . As is the case with the above described embodiments, the first circuit board  21  and the third circuit board  23   a  are disposed to extend substantially horizontally. 
   The second circuit  22  is disposed to extend substantially vertically between the first circuit board  21  and the third circuit board  23   a  with the horizontal gap  80  provided between the second circuit  22  and the third circuit board  23   a . However, in the present embodiment, the second circuit board  22   b  is disposed to extend substantially parallel with the side plates  14 . 
   With the above arrangement of the electronic apparatus  100   b , heat generated by the ICs  33  on the second circuit board  22   b  acts to heat the air surrounding the ICs  33 . Consequently, upward air flows are generated, which pass through the horizontal gap  80 . Then, the upward air flows are discharged through the exhaust ports  17  arranged above the gap  80 . This causes generation of air flows entering the intake ports  16  and  16   a , then passing between the circuit boards  21  and  22   b  and  23   a  and  24 , between each of the circuit boards  21 ,  22   b ,  23   a , and  24  and the casing  10 , and through the horizontal gap  80 , and finally being discharged through the exhaust ports  17   a . Consequently, the interior of the casing  10   a  can be efficiently ventilated to effectively cool the circuit boards  21 ,  22   b ,  23   a , and  24 , the power source  31 , and the expansion card  32 . 
   Further, since the second circuit board  22   b  is disposed to extend substantially parallel with the side plates  14 , the second circuit board  22   b  or one or more other circuit boards, not shown, which are parallel with the second circuit board  22   b , can be cooled without blocking air flows flowing in through the intake ports  16  and passing under the first circuit board  21 . 
   In the above described embodiments, a mixing apparatus for audio signals is illustrated as the electronic apparatus. However, similar effects can be produced by applying the present invention to other electronic apparatuses such as a personal computer and audio visual equipment.