Abstract:
An electronic device includes: a metal housing with an opening; a metal lid that is attached to the housing so as to cover the opening; a first substrate fixed in the housing and spread facing and parallel to the opening; two connectors that are fixed in the housing at a position facing and closer to the opening than the first substrate and are spread facing and parallel to the opening, the two connectors extending parallel to each other such that there is a predetermined space between the two connectors, the two connectors each being capable of receiving a second substrate that is inserted therein toward the space; and a metal plate member disposed in the space so that the metal plate member is fastened to the housing and resiliently contacts a surface of the first substrate, thereby electrically connecting a ground of the first substrate to the housing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an electronic device that has a substrate mounted with an electronic circuit and accommodated in a housing and to a metal plate member employed in the electronic device. 
         [0003]    2. Description of the Related Art 
         [0004]    Recently, various types of mobile personal computers (abbreviated as PC hereinafter) have come into widespread use. One such a PC is a so-called notebook PC composed of a main unit incorporating an arithmetic circuit and having a keyboard on the front surface thereof and a display unit having a display screen and being capable of folded onto the main unit. Another type of such a PC is a pure-tablet (slate) PC that incorporates an arithmetic circuit and has a display screen on the top surface thereof, to which a keyboard is optionally externally connected. 
         [0005]    Such mobile PCs are made thinner to reduce the overall size and weight while maintaining the required display screen size. For further reduction in size and weight, a metal housing is often employed, which is also useful to provide an electromagnetic shield between the inside and the outside of the housing. 
         [0006]    Additionally, a cable or the like used for connection to another device compromises the mobility of such mobile PCs, so that many mobile PCs incorporate radio communication features conforming to various standards, such as the wireless LAN and the Bluetooth (registered trademark). When a mobile PC incorporates radio communication features, it needs a reliable electromagnetic shield and a countermeasure for suppressing noise due to radio wave generated by an internal circuit. 
         [0007]    For example, in Japanese Patent Laid-Open No. 2005-75301, there is proposed the device housed in a metal casing and having shot-range radio communication functions such as the Bluetooth that suppresses radio wave noise without compromising performance of transmitting and receiving radio waves. 
         [0008]    Meanwhile, conventional measures against noise have needed certain space in a device for suppressing noise, which is becoming difficult due to the latest demand for a thinner and lighter device. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention has been made in view of the above circumstances and provides an electronic device that utilizes a narrow space so as to realize measures against radio wave noise and a metal plate member employed in the electronic device. 
         [0010]    An electronic device according to the present invention includes: 
         [0011]    a metal housing with an opening; 
         [0012]    a metal lid that is attached to the housing so as to cover the opening; 
         [0013]    a first substrate that is fixed in the housing and is spread facing and parallel to the opening; 
         [0014]    two connectors that are fixed in the housing at a position facing the opening and closer to the opening than the first substrate and that are spread facing and parallel to the opening, the two connectors extending parallel to each other such that there is a predetermined space between the two connectors, the two connectors each being capable of receiving a second substrate that is inserted therein toward the space from a side of the connector opposite to the space; and 
         [0015]    a metal plate member disposed in the space so that the metal plate member is fastened to the housing and is in resilient contact with a surface of the first substrate, thereby electrically connecting a ground of the first substrate to the housing. 
         [0016]    In a typical notebook PC or pure-tablet PC, two connectors are placed on the main board which is the first substrate, so as to incorporate the sub substrate which is the second substrate such as a memory board for increasing memory capacity. 
         [0017]    The electronic device according to the invention utilizes a dead space between the two connectors by placing the metal plate member in the space and fastening the metal plate member to the metal housing. This allows better use of a narrow space as well as suppression of radio wave noise by electrically connecting the ground of the first substrate to the metal housing. 
         [0018]    Here, it is preferable that the metal plate member includes a base part and two resilient contact pieces, the base part being disposed in the space such that the base part is spread parallel to the two connectors and both ends of the base part is fastened to the housing, the two resilient contact pieces being spread from the respective ends of the base part toward a substantial center of the base part while facing the first substrate so that tips of the resilient contact pieces contact the first substrate. 
         [0019]    As described above, the metal plate member is composed of the base part and the two resilient contact pieces. Provision of the base part securely fastens the metal plate member to the housing with the ends of the metal plate member fastened to the housing. Additionally, the two resilient contact pieces make the ground of the first substrate to be electrically connected to the housing at a position near the ends of the base part fastened to the housing. 
         [0020]    Here, it is preferable that the second substrate is typically a memory board mounted with a memory. More preferably, the housing is made of a magnesium alloy for making the device thinner and lighter while maintaining strength. 
         [0021]    Further, the electronic device according to the invention may be typically a mobile computer, a so-called pure-tablet (slate-type PC) PC, having a tabular form as a whole that houses in the housing an electronic circuit for data processing and has a display screen fixed to a surface of the computer. 
         [0022]    The present invention can be preferably employed to the so-called pure-tablet (slate) PC for which the demand for a thinner device is often made and on which internal components are closely mounted. 
         [0023]    Additionally, the metal plate member in the electronic device according to the present invention can realize features described above. 
         [0024]    As described above, the electronic device according to the present invention is capable of reducing radio wave noise effectively by better utilizing a narrow space. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a perspective view of a slate PC, which is an electronic device according to an embodiment of the present invention, seen from the top surface having a display screen formed thereon; 
           [0026]      FIG. 2  is a perspective view of the slate PC shown in  FIG. 1  seen from the bottom surface; 
           [0027]      FIG. 3  is a schematic view of the slate PC  10  shown in  FIG. 1 , seen from the front side; 
           [0028]      FIG. 4  is a schematic view of the slate PC  10  shown in  FIG. 1 , seen from the left side; 
           [0029]      FIG. 5  is a schematic view of the slate PC  10  shown in  FIG. 1 , seen from the rear side; 
           [0030]      FIG. 6  is a schematic view of the slate PC  10  shown in  FIG. 1 , seen from the right side; 
           [0031]      FIG. 7  shows the bottom surface of the slate PC shown in  FIG. 1 ; 
           [0032]      FIG. 8  is an enlarged perspective view of the inside of an opening shown in  FIG. 7 ; 
           [0033]      FIG. 9  is a perspective view of a metal plate member; 
           [0034]      FIG. 10  is a perspective view of the metal plate member in  FIG. 9  shown upside down; 
           [0035]      FIG. 11  shows the metal plate member placed in the opening; 
           [0036]      FIG. 12  shows the inside of a housing, with an image display panel being removed from the top surface of the slate PC shown in  FIG. 1 ; 
           [0037]      FIG. 13  is an enlarged view of a sub substrate disposed in the housing; 
           [0038]      FIG. 14  is a perspective view of the sub substrate removed from the housing; 
           [0039]      FIG. 15  is a perspective view showing the bottom of the sub substrate; 
           [0040]      FIG. 16  shows a flexible substrate for connecting the sub substrate and a main substrate to each other; 
           [0041]      FIG. 17  shows a connector on the sub substrate and a connector on the main substrate connected to each other via the flexible substrate shown in  FIG. 16 ; 
           [0042]      FIG. 18  shows the flexible substrate connecting the sub substrate and the main substrate to each other and held by a keep plate; 
           [0043]      FIG. 19  shows the inside of an opening formed in the bottom surface of the slate PC (see  FIG. 2 ) by removing a lid that covers the opening; 
           [0044]      FIG. 20  is an enlarged view of a cooling fan in the housing shown in  FIG. 12 ; 
           [0045]    Part (A) of  FIG. 21  shows the interior of the housing after the cooling fan is removed; 
           [0046]    Part (B) of  FIG. 21  shows the cooling fan removed from the housing; 
           [0047]      FIG. 22  is an exploded perspective view of the interior of the housing after the cooling fan is removed and the cooling fan removed from the housing; 
           [0048]      FIG. 23  shows the main substrate with a heat radiator component mounted thereon, removed from the housing, with the surface facing the bottom of the housing facing upward; 
           [0049]      FIG. 24  is an exploded perspective view showing the same surface of the main substrate as shown in  FIG. 23  and the heat radiator component after the heat radiator component is removed from the main substrate; 
           [0050]    Part (A) of  FIG. 25  shows the same surface of the main substrate as shown in  FIGS. 23 and 24  after the heat radiator component is removed; 
           [0051]    Part (B) of  FIG. 25  shows the surface of the heat radiator component intended to come into contact with the main substrate; and 
           [0052]      FIG. 26  shows the upper surface, which is the same surface as shown in  FIG. 12 , of the main substrate removed from the housing. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0053]    In the following, an embodiment of the present invention will be described. 
         [0054]    [Overall Configuration] 
         [0055]      FIG. 1  is a perspective view of a slate PC, which is an electronic device according to an embodiment of the present invention, seen from the top surface having a display screen formed thereon.  FIG. 2  is a perspective view of the slate PC shown in  FIG. 1  seen from the bottom surface. 
         [0056]    A slate PC  10  has a housing made of a magnesium alloy that forms the bottom surface and the side surfaces of the slate PC  10  and an image display panel that has a display screen for displaying images and covers the front of the housing with the display screen facing outwardly. The housing and the image display panel form the exterior of the slate PC  10 . 
         [0057]    On the front surface of the slate PC  10 , the image display panel is disposed with a display screen  11  facing outwardly. Two infrared communication windows  12   a  and  12   b  and a fingerprint sensor  13  are arranged around the image display panel. 
         [0058]    The infrared communication windows  12   a  and  12   b  are intended for infrared communication with a keyboard (not shown) separate from the slate PC  10 , for example, and receive keyboard manipulation information by infrared communication. The fingerprint sensor  13  is intended for authentication and can be configured so that the slate PC  10  can be operated only when the fingerprint detected by the fingerprint sensor  13  matches with the fingerprint of an authenticated user. 
         [0059]    In addition, a speaker opening  14 , two microphone openings  15   a  and  15   b,  a power supply button  16 , various push buttons  17  and  18  and various indicators  19  are disposed along the circumference of the top surface of the slate PC  10 , and a part of a battery pack  20  can be seen on the top surface of the slate PC  10 . 
         [0060]    In addition, as shown in  FIG. 2 , the slate PC  10  has, on the bottom surface thereof, a battery pack  20 , an unlock element  21  for removing the battery pack, a lid  22  that is opened when mounting a memory board in the slate PC  10 , a lid  23  that is opened when mounting or removing a hard disk, a Bluetooth module and a wireless LAN module in the slate PC  10 , a connector  24  to connect to a port replicator (not shown) and the like. Here, the lid  22  is made of an aluminum alloy, and the lid  23  is made of plastic whose inner surface is plated. These lids serve to electromagnetically shield the interior in cooperation with the housing made of a magnesium alloy that forms the bottom surface and the side surfaces of the slate PC  10 . The arrangement inside the lid  22  and the arrangement inside the lid  23  will be described later. 
         [0061]      FIG. 3  is a schematic view of the slate PC  10  shown in  FIG. 1 , seen from the front side. 
         [0062]    From left to right in  FIG. 3 , the slate PC  10  has, on this side, two USB connector ports  30  and  31 , a headphone connector port  32 , a microphone connector port  33 , an IEEE 1394 connector port  34 , a VGA connector housing section  35 , a LAN connector port  36 , a MODEM connector port  37 , a security lock hole  38 , and a DC power supply connector port  39 . 
         [0063]      FIG. 4  is a schematic view of the slate PC  10  shown in  FIG. 1 , seen from the left side. From left to right in  FIG. 4 , a pen housing opening  40 , a PC card insertion port  41 , a smart card insertion port  42 , a medium insertion port  43  configured to removably receive plural kinds of media, and an air exhaust port  44  for air cooling of the interior are arranged on this side. Here, the pen (not shown) is an input device that inputs, by touching the display screen  11  (see  FIG. 1 ), an instruction corresponding to an icon or the like displayed at the point that the pen touches. 
         [0064]      FIG. 5  is a schematic view of the slate PC  10  shown in  FIG. 1 , seen from the rear side. 
         [0065]    On this side, a wireless LAN antenna housing section  50  and a Bluetooth antenna housing section  51  are provided. 
         [0066]      FIG. 6  is a schematic view of the slate PC  10  shown in  FIG. 1 , seen from the right side. 
         [0067]    This drawing shows the side of the slate PC  10  with the battery pack  20  shown in  FIGS. 1 and 2  mounted thereon. 
         [0068]    Since the battery pack  20  is attached to this side, any other features are not provided on this side. 
         [0069]    [Arrangement Inside Lid] 
         [0070]      FIG. 7  shows the bottom surface of the slate PC  10 . In  FIG. 7 , the lid  22  shown in  FIG. 2  is omitted, and the inside of the opening that would otherwise be covered with the lid  22  can be seen. 
         [0071]      FIG. 8  is an enlarged perspective view of the inside of the opening shown in  FIG. 7 . 
         [0072]    In  FIGS. 7 and 8 , a metal plate member  70  (see  FIGS. 9 through 11 ) described later is also omitted. 
         [0073]    As described above, the bottom surface and the side surfaces of the slate PC  10  are covered by the housing made of a magnesium alloy, openings formed in the bottom surface of the housing are covered with the lids  22  and  23  made of an aluminum alloy (see  FIG. 2 ), and the lids  22  and  23  are screwed to the housing. Thus, the lids  22  and  23  are electrically connected to the housing, thereby forming a rigid electromagnetic shield. 
         [0074]    An opening  60  shown in  FIGS. 7 and 8  is one of the openings formed in the bottom surface of the housing. If the lid  22  shown in  FIG. 2  is screwed to the housing at three threaded parts  60   a,    60   b  and  60   c  the opening  60  is closed. If the three screws are removed, the inside of the opening  60  can be exposed as shown in  FIGS. 7 and 8 . 
         [0075]    A main substrate  61  facing the opening  60  and extending parallel to the opening  60  on which a CPU (not shown) that performs arithmetic processings is mounted is fixed in the housing. On the surface of the main substrate  61  facing the opening  60 , two connectors  62   a  and  62   b  are mounted in the approximate middle of the area that can be seen in the opening  60 . The two connectors  62   a  and  62   b  are arranged on a plane parallel to the opening  60  and extend parallel to each other with a space  63  formed therebetween. A memory board on which a memory is mounted is inserted into the connectors  62   a  and  62   b  from the side opposite to the space  63  (toward the space  63 ) in a position parallel to the main substrate  61 . 
         [0076]      FIGS. 7 and 8  show only one memory board  64  inserted into one of the two connectors  62   a  and  62   b,  specifically, the connector  62   a.  To increase the memory capacity, another memory board can be inserted into the remaining connector, or the memory board currently inserted in the connector can be replaced with a memory board on which a memory with a higher capacity is mounted. 
         [0077]    In addition, threaded parts  65   a  and  65   b,  which are protruding parts of the housing, are formed at opposite ends of the space  63 . A metal plate member  70  described below is screwed to the threaded parts  65   a  and  65   b.    
         [0078]      FIG. 9  is a perspective view of the metal plate member  70 , and  FIG. 10  is a perspective view of the metal plate member  70  in  FIG. 9  shown upside down. 
         [0079]      FIG. 11  shows the metal plate member placed in the opening. 
         [0080]    The metal plate member  70  has a base part  71  having screw holes  71   a  and  71   b  formed at the opposite ends thereof, and two resilient contact pieces  72   a  and  72   b  formed by bending parts of the base part  71 . When the metal plate member  70  is mounted in the opening  60  ( FIGS. 7 and 8 ), the base part  71  is placed in the space  63  in the opening, extends parallel to the two connectors  62   a  and  62   b  and is screwed, at the opposite ends having the screw holes  71   a  and  71   b,  to the threaded parts  65   a  and  65   b  ( FIGS. 7 and 8 ) of the housing. 
         [0081]    The two resilient contact pieces  72   a  and  72   b  extend from the opposite ends of the base part  71  toward the approximate center thereof and to the main substrate  61  ( FIGS. 7 and 8 ) so that the tips thereof come into resilient contact with the main substrate  61 . A ground pattern is formed on the main substrate  61  at areas with which the resilient contact pieces  72   a  and  72   b  come into contact. If the metal plate member  70  is mounted, the ground on the main substrate  61  and the housing made of a metal (a magnesium alloy) are electrically connected to each other. Thus, such a narrow space can be effectively used to effectively reduce the radio noise. 
         [0082]    [Arrangement for Mounting or Removing Component] 
         [0083]      FIG. 12  shows the inside of the housing, with the image display panel being removed from the top surface of the slate PC shown in  FIGS. 1 and 2 . 
         [0084]    The slate PC  10  has a housing  80  made of a magnesium alloy that forms the bottom surface and the side surfaces of the slate PC  10 , and various components are arranged in the housing  80 . 
         [0085]    Of the components, those that will be involved in the following description include the main substrate  61  on which the CPU (not shown) that performs arithmetic processings or the like is mounted, a sub substrate  90  on which a PC card slot  91  into which a PC card is inserted or the like is mounted, and a cooling fan  100  for air cooling. In addition, a heat transfer plate  110  is screwed to the surface of the main substrate  61  that can be seen in  FIG. 12 . The heat transfer plate  110  will be described later. 
         [0086]      FIG. 13  is an enlarged view of the sub substrate  90  disposed in the housing  80 . In  FIG. 13 , screws for securing the sub substrate  90  to the housing and components (i.e. a flexible substrate and a keep plate described later) for coupling the sub substrate  90  and the main substrate  61  with each other are omitted. The sub substrate  90  has four screw holes  90   a,    90   b,    90   c  and  90   d  and is secured to the housing  80  by screws inserted into the screw holes  90   a,    90   b,    90   c  and  90   d.  One of the screws inserted into the screw holes  90   a,    90   b,    90   c  and  90   d,  specifically, the screw inserted into the screw hole  90   b  is used also to secure the keep plate described later. 
         [0087]    The sub substrate  90  and the main substrate  61  are fixed at different heights in the housing  80 . This is intended to make the slate PC  10  thinner by reducing the dead space in the direction along the thickness of the slate PC  10  produced by the difference in thickness between the components mounted on the sub substrate  90  and the main substrate  61 . The sub substrate  90  and the main substrate  61  fixed in the housing  80  are adjacent to each other at respective border areas. In the border areas, a pair of connectors  92  and  111  for interconnecting the sub substrate  90  and the main substrate  61  are provided. 
         [0088]      FIG. 14  is a perspective view of the sub substrate removed from the housing, and  FIG. 15  is a perspective view showing the bottom of the sub substrate. In  FIGS. 14 and 15 , a smart card  120  is mounted. 
         [0089]    On one surface of the sub substrate  90 , there is mounted the PC card slot  91  into which the PC card (not shown) is inserted through the PC card insertion port  41  shown in  FIG. 4  for access. On the other surface of the sub substrate  90 , there is mounted a smart card slot  93  into which the smart card  120  is inserted through the smart card insertion port  42  shown in  FIG. 4  for access. The smart card slot  93  has a smaller footprint on the sub substrate  90  than the PC card slot  91 , and therefore, a Bluetooth module  94  for enabling radio communication conforming to the Bluetooth standard is additionally mounted on the same surface as the smart card slot  93 . The Bluetooth module  94  is screwed to the sub substrate  90  and connected to the sub substrate  90  via a connector  95  and can be easily removed from the sub substrate  90 . 
         [0090]      FIG. 16  shows a flexible substrate  130  for connecting the sub substrate and the main substrate to each other. 
         [0091]    The flexible substrate  130  has a stepped configuration, and connectors  131  and  132  are provided on the flexible substrate  130 , one for each step. The height of the step of the flexible substrate  130  corresponds to the height difference between the sub substrate  90  and the main substrate  61  fixed in the housing  80 . The connector  131  on the flexible substrate  130  is coupled to the connector  92  (see  FIG. 13 ) on the sub substrate  90 , and the connector  132  on the flexible substrate  130  is coupled to the connector  111  (see  FIG. 13 ) on the main substrate  61 . In this way, the sub substrate  90  and the main substrate  61  are electrically connected to each other via the flexible substrate  130 . 
         [0092]      FIG. 17  shows the connector on the sub substrate and the connector on the main substrate connected to each other via the flexible substrate shown in  FIG. 16 . 
         [0093]    The two connectors on the flexible substrate  130  are coupled to the connector on the sub substrate  90  and the connector on the main substrate  61 .  FIG. 17  shows the back side of the flexible substrate  130 , which is opposite to the side shown in  FIG. 16 . 
         [0094]      FIG. 18  shows the flexible substrate connecting the sub substrate and the main substrate to each other and held by a keep plate. 
         [0095]    A keep plate  135  is made of a metal (steel) and is intended to prevent the flexible substrate  130  from unexpectedly dropping off and to firmly electrically connect a ground on the sub substrate  90  and a ground on the main substrate  61  to each other. The keep plate  135  is secured by two screws  136   a  and  136   b  and connected to the ground on the sub substrate  90  by the screw  136   a  and to the ground on the main substrate  61  by the screw  136   b.    
         [0096]      FIG. 19  shows the inside of the opening formed in the bottom surface of the slate PC (see  FIG. 2 ) by removing the lid  23  that covers the opening. 
         [0097]    The lid  23  shown in  FIG. 2  is made of plastic, and the inner surface is plated. The lid  23  is screwed to the housing at four threaded parts  130   a,    130   b,    130   c  and  130   d,  which are part of the housing, and serves as an electrical shield in cooperation with the housing. 
         [0098]    When the lid  23  is removed, in the approximate middle of the opening  230  in the housing, there can be seen a hard disk unit mounting part  136  on which a hard disk unit (not shown) is removably mounted. At the left of the opening  230  in  FIG. 19 , the Bluetooth module  94  mounted on the sub substrate  90  is exposed. In addition, at the left front of the opening  230  in  FIG. 19 , a Bluetooth antenna  96  connected to the Bluetooth module  94  is also arranged. The Bluetooth module  94  and the Bluetooth antenna  96  can be easily mounted and removed. 
         [0099]    In addition, at the right of the opening  230  in  FIG. 19 , a wireless LAN module  116  mounted on the main substrate  61  is exposed. In addition, at the right front of the opening  230  in  FIG. 19 , a wireless LAN antenna  117  is also exposed. 
         [0100]    The wireless LAN module  116  is connected to the main substrate  61  via a connector  118  and can easily mounted thereon and removed therefrom. The wireless LAN antenna  117  is connected to the main substrate  61  via a connector  119  and screwed to the housing and can be easily mounted thereon and removed therefrom. 
         [0101]    The hard disk unit, the Bluetooth module  94  (including the Bluetooth antenna  96 ) and the wireless LAN module  116  (inducing the wireless LAN antenna  117 ) may not be mounted depending on the destination. According to this embodiment, the modules mounted on the separate two substrates, that is, the main substrate  61  and the sub substrate  90 , and the hard disk unit are arranged in the single opening  230 , and simply removing the single lid  23  (see  FIG. 2 ) enables mounting and removal of these components. Thus, the arrangement can be easily adapted to the specifications of the destination. 
         [0102]    According to the present embodiment, the position of the Bluetooth module  94  mounted on the sub substrate  90  and the position of the wireless LAN module  116  mounted on the main substrate  61  according to this embodiment correspond to a first component mounting part and a second component mounting part according to the present invention, respectively. 
         [0103]    [Arrangement for Attaching Cooling Fan and Structure of Feat Radiator] 
         [0104]      FIG. 20  is an enlarged view of the cooling fan  100  in the housing shown in  FIG. 12 . 
         [0105]    The main substrate  61  is fixed in the housing  80  at a position spaced apart from the air exhaust port  44  shown in  FIG. 4 . The cooling fan  100  is disposed in the housing  80  in a space between the air exhaust opening  44  shown in  FIG. 4  and the main substrate  61 , screwed to the housing  80  and electrically connected to the main substrate  61  via the connector  132 . 
         [0106]    Part (A) of  FIG. 21  shows the interior of the housing after the cooling fan is removed, and Part (B) of  FIG. 21  shows the cooling fan removed from the housing.  FIG. 22  is an exploded perspective view of the interior of the housing after the cooling fan is removed and the cooling fan removed from the housing. 
         [0107]    In the housing  80 , apart  151  of a heat radiator component  150  for supporting the bottom surface of the cooling fan  100  that faces the inside of the housing is exposed at the position where the cooling fan  100  is mounted. The heat radiator component  150  extends to a position immediately inside the air exhaust port  44  shown in  FIG. 4 , and a heat radiating fin  152  is disposed on the heat radiator component  150  at a position immediately inside the air exhaust port  44 . 
         [0108]      FIG. 23  shows the main substrate with the heat radiator component mounted thereon, removed from the housing, such that the surface of the main substrate facing the bottom of the housing (the surface opposite to that shown in  FIGS. 21 and 22 ) faces upward in the figure.  FIG. 24  is an exploded perspective view showing the same surface of the main substrate as shown in  FIG. 23  and the heat radiator component after the heat radiator component is removed from the main substrate. Part (A) of  FIG. 25  shows the same surface of the main substrate as shown in  FIGS. 23 and 24  after the heat radiator component is removed, and Part (B) of  FIG. 25  shows the surface of the heat radiator component intended to come into contact with the main substrate (the surface opposite to that shown in  FIGS. 23 and 24 ). 
         [0109]    As shown in  FIGS. 23 to 25 , in addition to the part  151  for supporting the cooling fan  100  and the heat radiating fin  152 , the heat radiator component  150  has a first flat-plate heat receiving part  153  having a protrusion  153   a  extending toward the main substrate  61 , a second flat-plate heat receiving part  154  and a part  155  for supporting the heat radiating fin  152  as well as a heat transfer pipe (heat transfer member)  156  that is fixed to a side of the first heat receiving part  153  at one end and in contact with the second heat receiving part  154  and extends to the heat radiating fin  152 . The heat transfer pipe  156  serves to receive heat from the first heat receiving part  153  and the second heat receiving part  154  and efficiently transfer the heat to the heat radiating fin  152 . 
         [0110]    On the surface of the main substrate  61  on which the heat radiator component  150  is mounted, two heat generating components that require forced cooling, specifically, a chip set  143  and a CPU  144 , are mounted. The protrusion  153   a  of the first heat receiving part  153  and the second heat receiving part  154  of the heat radiator component  150  are designed to come into intimate contact with the upper surfaces of the chip set  143  and the CPU  144 , respectively, with a heat transferring paste or elastic material (rubber) (not shown) interposed therebetween. 
         [0111]    The protrusion  153   a  of the first heat receiving part  153  is configured to compensate for the height difference between the chip set  143  and the CPU  144  on the main substrate  61 , thereby making both the chip set  143  and the CPU  144  come into intimate contact with the heat radiator component  150 . As shown in  FIG. 25 , the heat radiator component  150  has six screw holes  157   a  to  157   f.  Of the six screw holes  157   a  to  157   f,  five screw holes  157   a  to  157   e  are used to secure the heat radiator component  150  to the main substrate  61  by screws passing through five screw holes  145   a  to  145   e  penetrating the main substrate  61 . The remaining one screw hole  157   f  is used for securing other components. 
         [0112]    Heat generated by the chip set  143  and the CPU  144  is absorbed by the first heat receiving part  153  and the second heat receiving part  154  and transferred to the heat transfer pipe  156 . The heat is further transferred to the heat radiating fin  152  via the heat transfer pipe  156 . The heat radiating fin  152  receives the air supplied from the cooling fan  100 , heat is transferred from the heat radiating fin  152  to the air, and the heated air is discharged to the outside through the air exhaust port  44  shown in  FIG. 4 . 
         [0113]    As shown in  FIGS. 20 and 22 , the cooling fan  100  is disposed, on the heat radiator component  150  extending near the bottom of the housing, between the heat radiating fin  152  disposed immediately inside the air exhaust port  44  and the main substrate  61  and screwed to the housing  80 . Therefore, the cooling fan  100  can be replaced without removing the main substrate  61  or the heat radiator component  150 . Thus, the workability of replacing the cooling fan  100  is improved. 
         [0114]      FIG. 26  shows the upper surface, which is the same surface as shown in  FIG. 12  (the surface opposite to that shown in  FIG. 23 ), of the main substrate removed from the housing. In  FIG. 26 , the heat transfer plate  110  is removed from the main substrate. 
         [0115]    On the surface of the main substrate  61  shown in  FIG. 26 , an I/O controller  146 , which is a heat generating component that requires forced cooling, is mounted. 
         [0116]    The I/O controller  146  is in intimate contact with a heat receiving part  110   a  of the heat transfer plate  110  via a heat transferring adhesive (not shown) and secured to the main substrate  61  by screws fitted into screw holes  147   a  and  147   b  in the main substrate. Heat absorbed by the heat receiving part  110   a  of the heat transfer plate  110  is transferred to a heat transferring part  110   b  of the heat transfer plate  110 . The heat transferring part  110   b  is secured to the heat radiator component  150  disposed on the opposite surface of the main substrate  61  by three screws  170   a  to  170   c  passing through the three screw holes  145   a  to  145   c  in the main substrate. Thus, the heat transferred to the heat transferring part  110   b  of the heat transfer plate  110  is transferred to the heat radiator component  150  fixed to the opposite surface of the main substrate  61  via the fixing screws. That is, the heat generated by the I/O controller  146  is transferred through the heat transfer plate  110  and the fixing screws  170   a  to  170   c  to the heat radiator component  150  fixed to the opposite surface of the main substrate  61  and then to the heat radiating fin  152  on the heat radiator component  150  through the heat radiator component  150  and discharged to the outside through the medium of the air supplied from the cooling fan  100 . 
         [0117]    As described above, according to this embodiment, heat generated by heat generating components mounted on either side of the main substrate  61  can be efficiently transferred and discharged even if the main substrate  61  is disposed in a narrow space.