Patent Publication Number: US-2015084490-A1

Title: Electronic apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/882,551, filed Sep. 25, 2013, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to an electronic apparatus. 
     BACKGROUND 
     An electronic apparatus comprising a fan, a heat sink and a heat pipe is provided. 
     Improvement in cooling performance of electronic apparatuses is required. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A general architecture that implements the various features of the embodiments will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate the embodiments and not to limit the scope of the invention. 
         FIG. 1  is a perspective illustration of an electronic apparatus according to one embodiment. 
         FIG. 2  is a cross-sectional view of the electronic apparatus illustrated in  FIG. 1 . 
         FIG. 3  is a back view of the electronic apparatus illustrated in  FIG. 1 . 
         FIG. 4  is a bottom view of the electronic apparatus illustrated in  FIG. 1 . 
         FIG. 5  is a cross-sectional view of the electronic apparatus illustrated in  FIG. 1  (at an opening angle of 0°). 
         FIG. 6  is a cross-sectional view of the electronic apparatus illustrated in  FIG. 1  (at an opening angle of 105°). 
         FIG. 7  is a cross-sectional view of the electronic apparatus illustrated in  FIG. 1  (at an opening angle of 140°). 
         FIG. 8  is a cross-sectional view taken along line F 8 -F 8  of the electronic apparatus illustrated in  FIG. 2 . 
         FIG. 9  is a cross-sectional view illustrating a first modification of the electronic apparatus illustrated in  FIG. 1 . 
         FIG. 10  is a back view illustrating a second modification of the electronic apparatus illustrated in  FIG. 1 . 
         FIG. 11  is a cross-sectional view illustrating a third modification of the electronic apparatus illustrated in  FIG. 1 . 
         FIG. 12  is a cross-sectional view taken along line F 12 -F 12  line of the electronic apparatus illustrated in  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments will be described hereinafter with reference to the accompanying drawings. 
     In general, according to one embodiment, an electronic apparatus comprises a first housing, a heating component in the first housing, a first heat sink and a fan. The first housing comprises a first exhaust hole and a second exhaust hole. The first heat sink faces the first exhaust hole. The first heat pipe thermally connects the heating component and the first heat sink. The fan comprises a first discharge hole configured to discharge airflow passing the first heat sink and going to the first exhaust hole, and a second discharge hole configured to discharge airflow passing a circumference of the heating component and going to the second exhaust hole. 
     Various embodiments will be described hereinafter with reference to the accompanying drawings. 
     In this specification, some components are expressed by two or more terms. These terms are merely examples. Those components may be further expressed by another or other terms. And the other components which are not expressed by two or more terms may be expressed by another or other terms. 
       FIG. 1  to  FIG. 8  show an electronic apparatus  1  according to one embodiment. The electronic apparatus  1  is, for example, a notebook type of portable computer (i.e., a notebook PC). An electronic apparatus to which the present embodiment is applicable is not limited to the above example. The embodiment is widely applicable to various types of electronic apparatuses such as a television receiver, a tablet type (i.e., a slate type) of portable computer, a cellular phone (including a smartphone) and a game console. 
     As shown in  FIG. 1 , the electronic apparatus  1  comprises a first housing  2 , a second housing  3  and a pair of hinges  4   a  and  4   b . The first housing  2  is, for example, a main housing. For example, a circuit board  5  as a main board is housed in the first housing  2 . 
     The first housing  2  comprises an upper wall  11 , a lower wall  12  (i.e., a bottom wall) and a peripheral wall  13 , and is formed into a flat box shape. The upper wall  11  is an example of a first wall. The lower wall  12  is an example of a second wall. In this specification, upper, lower, right and left sides are defined from the perspective of a user. In addition, this specification defines a side close to a user as a front side, and defines a side distant from a user as a rear side. 
     The upper wall  11  extends longitudinally (e.g., substantially horizontally) with respect to the first housing  2 . A keyboard  14  as an input unit is attached to the upper wall  11 . The input unit of the upper wall  11  is not limited to a keyboard, and may be, for example, a touchpanel (i.e., a touchsensor) and other input devices. 
     The lower wall  12  is located on a side opposite to the upper wall  11 . The lower wall  12  extends substantially in parallel with, for example, the upper wall  11 . When the electronic apparatus  1  is placed on a desk, the lower wall  12  faces the top surface of the desk (i.e., external placement surface). The lower wall  12  comprises, for example, a plurality of legs  15  (i.e., supporters). When the electronic apparatus  1  is placed on a desk, the legs  15  make contact with the top surface of the desk and support the electronic apparatus  1 . 
     The peripheral wall  13  extends in a direction intersecting the upper wall  11  and the lower wall  12 , and connects the peripheral edge of the lower wall  12  and the peripheral edge of the upper wall  11 . The peripheral wall  13  extends in a thickness direction of the first housing  2 . The first housing  2  comprises a first end  2   a  (e.g., a front end), and a second end  2   b  (e.g., a rear end) on a side opposite to the first end  2   a.    
     The peripheral wall  13  comprises a front wall  16 , a rear wall  17 , a left wall  18  and a right wall  19 . The front wall  16  is located at the first end  2   a , and extends in a right-left direction (i.e., widthwise) of the first housing  2 . The rear wall  17  is located at the second end  2   b , and extends substantially in parallel with the front wall  16 . The rear wall  17  is an example of a third wall. The rear wall  17  extends from the rear end of the upper wall  11  to the rear end of the lower wall  12 . The left wall  18  and the right wall  19  extend in a front-back direction (i.e., depthwise) of the first housing  2 , and the front-back direction intersects the front wall  16  and the rear wall  17 . Each of the left wall  18  and the right wall  19  connects an end of the front wall  16  and an end of the rear wall  17 . 
     The first housing  2  comprises an upper cover  26  (i.e., a cover) and a lower cover  27  (i.e., a base). The upper cover  26  comprises a part of the peripheral wall  13 , and the upper wall  11 . The lower cover  27  comprises the rest of the peripheral wall  13 , and the lower wall  12 . The combination of the upper cover  26  and the lower cover  27  forms the first housing  2 . 
     On the other hand, the second housing  3  is, for example, a display housing. A display device  20  (i.e., a display module, a unit) is housed in the second housing  3 . A liquid crystal display device is an example of the display device  20 . However, the display device  20  is not limited to this example. The display device  20  comprises a display screen  20   a  configured to display an image. 
     The second housing  3  comprises a front wall  21  (i.e., a first wall), a rear wall  22  (i.e., a back wall, a second wall) and a peripheral wall  23  (i.e., a sidewall, a third wall), and is formed into a flat box shape. The front wall  21  comprises an opening  21   a  configured to expose the display screen  20   a . The rear wall  22  is located on a side opposite to the front wall  21 , and extends substantially in parallel with the front wall  21 . The rear wall  22  covers the rear surface of the display device  20 . The peripheral wall  23  extends in a direction intersecting the front wall  21  and the rear wall  22 , and connects the peripheral edge of the front wall  21  and the peripheral edge of the rear wall  22 . The second housing  3  comprises a first end  3   a  (e.g., a lower end), and a second end  3   b  (e.g., an upper end) on a side opposite to the first end  3   a.    
     The hinges  4   a  and  4   b  rotatably (i.e., openably and closably) attach the second end  2   b  of the first housing  2  to the first end  3   a  of the second housing  3 . This structure enables the electronic apparatus  1  to be opened and closed (i.e., to be changed in shape, to be folded). The second housing  3  is able to rotate between a first state (e.g., a closed state) and a second state (e.g., an opened state). 
     In the first state, the second housing  3  is piled on the first housing  2 , and the electronic apparatus  1  is closed. Specifically, the upper wall  11  of the first housing  2  and the front wall  21  of the second housing  3  are overlapped. Further, the display screen  20   a  and the keyboard  14  are hidden from the outside. On the other hand, in the second state, the second housing  3  stands relative to the first housing  2 , and thus the electronic apparatus  1  is open. In the second state, the display screen  20   a  and the keyboard  14  are exposed to the outside. In addition, in the second state, the first end  3   a  of the second housing  3  is positioned in horizontally relative to the rear wall  17  of the first housing  2 , and faces the rear wall  17  from the back (e.g., see  FIG. 6 ). 
     Next, a heat dissipation structure of the electronic apparatus  1  is explained. 
     As shown in  FIG. 2  and  FIG. 3 , the first housing  2  comprises a plurality of first exhaust holes  31  and a plurality of second exhaust holes  32 . The first exhaust holes  31  and the second exhaust holes  32  are both provided in the rear wall  17  of the first housing  2 , and open toward the same direction. 
     The plurality of first exhaust holes  31  and the plurality of second exhaust holes  32  are separately provided in a longitudinal direction (e.g., a right-left direction) of the rear wall  17 . The plurality of first exhaust holes  31  are arranged in line in the longitudinal direction of the rear wall  17 . The plurality of second exhaust holes  32  are arranged in line in the longitudinal direction of the rear wall  17 . 
     A closed portion  33  is provided between the plurality of first exhaust holes  31  and the plurality of second exhaust holes  32 . The closed portion  33  is larger than, for example, the first exhaust hole  31  or the second exhaust hole  32 . The closed portion  33  is larger than, for example, the length of a side of a heating component  40  explained later. 
     As illustrated in  FIG. 2 , the heating component  40  is mounted on the circuit board  5 . The heating component  40  is, for example, a CPU or a graphics chip. However, the heating component  40  is not limited to these examples. A first heat sink  41 , a first heat pipe  42 , a second heat sink  43 , a second heat pipe  44  and a fan  45  are housed in the first housing  2 . 
     The first heat sink  41  is provided as a separate unit from the fan  45 , and faces the plurality of first exhaust holes  31 . The first heat sink  41  is a fin unit in which a plurality of fins are allocated in line. The first heat sink  41  is located on a lateral side of the circuit board  5 , and does not overlap the circuit board  5  in the thickness direction of the first housing  2 . 
     The first heat pipe  42  extends between the heating component  40  and the first heat sink  41 , and thermally connects the heating component  40  and the first heat sink  41 . In this structure, the heat generated by the heating component  40  when the electronic apparatus  1  is used is partially transferred to the first heat sink  41  by the first heat pipe  42 . In sum, the first remote heat exchange (RHE) type of heat dissipation structure is realized by the first heat sink  41 , the first heat pipe  42  and the fan  45 . 
     The second heat sink  43  is provided as a separate unit from the fan  45  at a position away from the fan  45 , and faces the plurality of second exhaust holes  32 . The second heat sink  43  is a fin unit in which a plurality of fins are arranged in line. The second heat sink  43  is located on the upper side (or the lower side) of the circuit board  5 , and overlaps the circuit board  5  in the thickness direction of the first housing  2 . 
     The second heat pipe  44  extends between the heating component  40  and the second heat sink  43 , and thermally connects the heating component  40  and the second heat sink  43 . In this structure, the heat generated by the heating component  40  at the time of using the electronic apparatus  1  is partially transferred to the second heat sink  43  by the second heat pipe  44 . Thus, the second remote heat exchange (RHE) type of heat dissipation structure is realized by the second heat sink  43 , the second heat pipe  44  and the fan  45 . 
     As shown in  FIG. 2 , the fan  45  (i.e., a cooling fan) is a centrifugal fan of bidirectional exhaust, and is provided near the second end  2   b  of the first housing  2 . The fan  45  is lateral to the circuit board  5 , and does not overlap the circuit board  5  in the thickness direction of the first housing  2 . The fan  45  comprises a fan case  47 , and an impeller  48  which is rotated and driven within the fan case  47 . The fan case  47  comprises a suction hole  50 , a first discharge hole  51  and a second discharge hole  52 . 
     The suction hole  50  opens on the upper and lower surfaces of the fan case  47 . The suction hole  50  of the lower surface of the fan case  47  faces the lower wall  12  of the first housing  2 . The lower wall  12  of the first housing  2  comprises a plurality of intake holes  54  facing the suction hole  50  of the fan  45  (refer to  FIG. 4 ). The fan  45  draws outer air (i.e., fresh air) of the first housing  2  through the intake holes  54  of the lower wall  12 . 
     As illustrated in  FIG. 2 , the first discharge hole  51  of the fan  45  is provided on a first side surface  47   a  of the fan case  47 , and opens toward the rear wall  17 . The first discharge hole  51  faces the first heat sink  41  and the plurality of first exhaust holes  31 . The first discharge hole  51  discharges airflow directed to the first exhaust holes  31  through the first heat sink  41 . In other words, the first discharge hole  51  discharges airflow in a direction (i.e., a first direction D 1 ) toward the rear wall  17  from the fan  45 . 
     On the other hand, the second discharge hole  52  is provided on a second side surface  47   b  which is different from the first side surface  47   a  in the fan case  47 . The second discharge hole  52  opens toward a direction which is different from, for example, the first discharge hole  51  by substantially 90 degrees. The second discharge hole  52  discharges airflow in a second direction D 2  intersecting (e.g., substantially orthogonal to) the first direction D 1 . 
     The second discharge hole  52  faces the heating component  40  mounted on the circuit board  5 . The second discharge hole  52  discharges airflow toward the heating component  40 . Specifically, the second discharge hole  52  discharges airflow which passes the circumference of the heating component  40  and then goes to the second exhaust holes  32  through the second heat sink  43 . 
     In the present embodiment, the heating component  40  is located between the second discharge hole  52  and the second exhaust holes  32 . As shown in  FIG. 2 , a guide  56  (e.g., a duct) is provided within the first housing  2 . The guide  56  guides the airflow which passed the circumference of the heating component  40  so as to head for the second exhaust holes  32 . The guide  56  leads the airflow discharged from the second discharge hole  52  of the fan  45  in the second direction D 2  to the first direction D 1 . The guide  56  may be formed by sponge located between the circuit board  5  and the inner surface of the first housing  2 , a rib provided in the inner surface of the first housing  2 , or the combination of the sponge and the rib. However, the guide  56  is not limited to these examples. 
     According to the above heat dissipation structure, by driving the fan  45 , airflow is discharged from the first discharge hole  51  toward the first heat sink  41 . This airflow takes heat from the first heat sink  41  during a process passing through the first heat sink  41 . After that, the airflow is discharged from the first exhaust holes  31  to the outside of the first housing  2 . 
     On the other hand, airflow is discharged directly toward the heating component  40  from the second discharge hole  52 . This airflow directly takes heat from the heating component  40  by moving around the heating component  40 . The airflow which passed the circumference of the heating component  40  is guided to the second heat sink  43  by the guide  56 . This airflow takes heat from the second heat sink  43  during a process passing through the second heat sink  43 . After that, the airflow is discharged from the second exhaust holes  32  to the outside of the first housing  2 . Thus, heat release of the heating component  40  is accelerated. 
     As shown in  FIG. 4  and  FIG. 5 , an airflow shield  57  is provided inside the first housing  2 . The airflow shield  57  is provided in order to block or reduce the air flow between the suction hole  50  and the discharge hole  51  or  52 . In this structure, the airflow discharged from the first or second discharge hole  51  or  52  is not absorbed into the fan  45  again before the airflow is discharged to the outside of the first housing  2 . 
     Next, the first and second exhaust holes  31  and  32  are explained in detail. As illustrated in  FIG. 2  and  FIG. 6 , the first and second exhaust holes  31  and  32  are provided in the rear wall  17  of the first housing  2 . Therefore, the first and second exhaust holes  31  and  32  face (e.g. are covered by) the second housing  3  when the second housing  3  is raised with respect to the first housing  2 . 
     As shown in  FIG. 5 , the rear wall  17  of the first housing  2  is formed into, for example, a circular arc shape ranging from the end of the upper wall  11  to the end of the rear wall  17 . Specifically, the rear wall  17  comprises an outmost portion  60  (e.g., a central portion), a first area  61  (e.g., an upper area) and a second area  62  (e.g., a lower area). The outmost portion  60  is located at the outermost position of the rear wall  17  in the direction from the fan  45  toward the rear wall  17 . The outmost portion  60  extends substantially across the full width of the first housing  2  along the longitudinal direction of the rear wall  17 . The outmost portion  60  includes a connected portion (e.g., a border, a joint surface) of the upper cover  26  and the lower cover  27 . 
     The first area  61  extends between the outmost portion  60  and the upper wall  11 . The first area  61  extends, inclining toward the upper wall  11  from the outmost portion  60 . The second area  62  is located at a side opposite to the first area  61  relative to the outmost portion  60 . The second area  62  extends between the outmost portion  60  and the lower wall  12 . The second area  62  extends, inclining toward the lower wall  12  from the outmost portion  60 . 
     In other words, the first area  61  and the second area  62  extend from the outmost portion  60  to opposite sides to each other (e.g., to the upper side and the lower side). Both of the first area  61  and the second area  62  incline toward the central side of the first housing  2 . In this specification, “to incline” refers to inclination relative to the thickness direction (e.g., substantially vertical direction) of the first housing  2 . In the present embodiment, the first area  61  and the second area  62  bend in a circular arc shape. However, the first area  61  and the second area  62  are not limited to this structure, and may be inclined surfaces which extend, for example, linearly inclining. 
     As illustrated in  FIG. 3  and  FIG. 5 , the plurality of first exhaust holes  31  include a plurality of first upper exhaust holes  31 A (i.e., first holes) provided in the first area  61 , and a plurality of first lower exhaust holes  31 B (i.e., second holes) provided in the second area  62 . The plurality of first upper exhaust holes  31 A are arranged in line in the longitudinal direction of the rear wall  17 , and the plurality of first lower exhaust holes  31 B are also arranged in line in the longitudinal direction of the rear wall  17 . 
     The plurality of first upper exhaust holes  31 A and the plurality of first lower exhaust holes  31 B are provided in a zigzag manner (i.e., in a staggered pattern) with respect to each other in such a way that the holes are alternately positioned along the longitudinal direction of the rear wall  17 . Thus, the plurality of first upper exhaust holes  31 A do not overlap (or less overlap) the plurality of first lower exhaust holes  31 B in the thickness direction of the first housing  2 . This structure improves strength of the first housing  2 . Further, when the first housing  2  is looked from above, the first lower exhaust holes  31 B are difficult to be seen through the first upper exhaust holes  31 A. In this manner, the design of the electronic apparatus  1  can be improved. 
     As illustrated in  FIG. 5 , the first upper exhaust holes  31 A are located above the outmost portion  60 . The first upper exhaust holes  31 A are provided in the first area  61  extending at a tilt. Thus, the first upper exhaust holes  31 A open on the rear side and upper side of the first housing  2 . The phrase “open on the upper side” means that the holes can be seen when they are looked from the direction perpendicular to the upper wall  11 . 
     On the other hand, the first lower exhaust holes  31 B are located below the outmost portion  60 . The first lower exhaust holes  31 B are provided in the second area  62  extending at a tilt, and open on the rear side and lower side of the first housing  2 . The phrase “open on the lower side” means that the holes can be seen when they are looked from the direction perpendicular to the lower wall  12 . 
     The first lower exhaust holes  31 B are larger than, for example, the first upper exhaust holes  31 A. The first lower exhaust holes  31 B are long holes which are longer than the first upper exhaust holes  31 A. The lower ends of the first lower exhaust holes  31 B reach a position equal to the lower wall  12  in a direction from the fan  45  toward the rear wall  17  (e.g., a direction substantially parallel to the lower wall  12 , or a substantially horizontal direction). 
     As shown in  FIG. 3 , similarly to the first exhaust holes  31 , the plurality of second exhaust holes  32  include a plurality of second upper exhaust holes  32 A (i.e., first holes) provided in the first area  61 , and a plurality of second lower exhaust holes  32 B (i.e., second holes) provided in the second area  62 . The plurality of second upper exhaust holes  32 A are allocated in line in the longitudinal direction of the rear wall  17 . The plurality of second lower exhaust holes  32 B are also arranged in line in the longitudinal direction of the rear wall  17 . 
     The plurality of second upper exhaust holes  32 A and the plurality of second lower exhaust holes  32 B are provided in a zigzag manner (i.e., in a staggered pattern) with respect to each other in such a way that the holes are alternately positioned along the longitudinal direction of the rear wall  17 . Therefore, the plurality of second upper exhaust holes  32 A do not overlap or less overlap the second lower exhaust holes  32 B in the thickness direction of the first housing  2 . In this structure, strength of the first housing  2  is improved. Further, when the first housing  2  is looked from above, the second lower exhaust holes  32 B are difficult to be seen through the second upper exhaust holes  32 A. Thus, the design of the electronic apparatus  1  can be improved. 
     The position, shape and size of the second upper exhaust holes  32 A are the same as, for example, the first upper exhaust holes  31 A. The position, shape and size of the second lower exhaust holes  32 B are the same as, for example, the first lower exhaust holes  31 B. Therefore, detailed explanation of the second upper exhaust holes  32 A or the second lower exhaust holes  32 B is omitted. 
     The above descriptions can be rephrased as follows. The first exhaust holes  31  include a portion located in one of the first area  61  and the second area  62 . The second exhaust holes  32  include a portion located in the other one of the first area  61  and the second area  62 . The first exhaust holes  31  may be provided in only one of the first area  61  and the second area  62 . In short, the first exhaust holes  31  may be only the first upper exhaust holes  31 A, or only the first lower exhaust holes  31 B. 
     The second exhaust holes  32  may be provided in only one of the first area  61  and the second area  62 . In other words, the second exhaust holes  32  may be only the second upper exhaust holes  32 A, or only the second lower exhaust holes  32 B. The number of first exhaust holes  31  or second exhaust holes  32  is not need to be more than one. For example, one hole may be employed as each of the member “first exhaust holes  31 ” and the member “second exhaust holes  32 ”. 
     Next, the positional relationships of the second housing  3  with the first exhaust holes  31  and the second exhaust holes  32  are explained. 
       FIG. 6  illustrates the electronic apparatus  1  at a first opening angle of θ1. The first opening angle of θ1 is, for example, an opening angle when the electronic apparatus  1  is ordinarily used. The first opening angle of θ1 is, for example, 100 to 110°. 
     At the first opening angle of θ1, the second housing  3  faces the first and second upper exhaust holes  31 A and  32 A from the rear side, but does not cover at least a part (e.g., the lower portion) of the first and second lower exhaust holes  31 B and  32 B. The second housing  3  does not cover the lower portion of the first and second lower exhaust holes  31 B and  32 B. In other words, the first and second lower exhaust holes  31 B and  32 B open downward. Therefore, part of the airflow moving from the fan  45  to the rear wall  17  is effectively discharged from the first and second lower exhaust holes  31 B and  32 B. 
     A recess  64  facing the rear wall  17  of the first housing  2  is provided at the first end  3   a  of the second housing  3 . The recess  64  is depressed in a circular arc shape along the rear wall  17  of the first housing  2 . By the placement of the recess  64 , a certain gap is ensured at all times between the first lower exhaust holes  31 B and the second housing  3 , and between the second lower exhaust holes  32 B and the second housing  3 . Therefore, part of the airflow moving from the fan  45  to the rear wall  17  is easily discharged from the first and second lower exhaust holes  31 B and  32 B. In addition, there is a gap between the first upper exhaust holes  31 A and the second housing  3 , and between the second upper exhaust holes  32 A and the second housing  3 . Thus, part of the airflow heading from the fan  45  for the rear wall  17  can be also discharged from the first and second upper exhaust holes  31 A and  32 A. 
     On the other hand,  FIG. 7  shows the electronic apparatus  1  at a second opening angle of θ2. At the second opening angle of θ2, the second housing  3  is largely rotated in such a way that, for example, several people can look at a screen. The second opening angle of θ2 is larger than the first opening angle of θ1. The second opening angle of θ2 is, for example, 140°. However, the second opening angle of θ2 is not limited to this example. 
     At the second opening angle of θ2, the first end  3   a  of the second housing  3  is located obliquely below the first and second lower exhaust holes  31 B and  32 B. The first end  3   a  of the second housing  3  faces, for example, substantially the whole area of the first and second lower exhaust holes  31 A and  32 B from rearward and downward. On the other hand, a gap g 2  between the second housing  3  and each of the first and second upper exhaust holes  31 A and  32 A is larger than a gap g 1  between the second housing  3  and each of the first and second upper exhaust holes  31 A and  32 A at the first opening angle of θ1. The gap g 2  between the second housing  3  and each of the first and second upper exhaust holes  31 A and  32 A is larger than, for example, a gap between the first sink  41  and the rear wall  17 . 
     Therefore, part of the airflow moving from the fan  45  to the rear wall  17  is effectively discharged from the first and second upper exhaust holes  31 A and  32 A. By the placement of the recess  64  in the second housing  3 , a gap is also provided between the second housing  3  and each of the first and second lower exhaust holes  31 B and  32 B. Thus, part of the airflow going from the fan  45  to the rear wall  17  can be also discharged from the first and second lower exhaust holes  31 B and  32 B. 
     As shown in  FIG. 8 , the second heat sink  43  overlaps the circuit board  5  in the thickness direction of the first housing  2 . This differentiates the height of the first heat sink  41  from the height of the second heat sink  43  within the first housing  2 . 
     In sum, as illustrated in  FIG. 6 , the first heat sink  41  and the second heat sink  43  are provided in such a way that they are out of alignment each other in a rotation direction R of the second housing  3 . In other words, the first heat sink  41  and the second heat sink  43  are provided at positions shifted from each other in the thickness direction of the first housing  2  (i.e., a direction from the upper wall  11  to the lower wall  12 ). 
     The first heat sink  41  faces, for example, the first upper exhaust holes  31 A and the first lower exhaust holes  31 B. The second heat sink  43  faces, for example, the second upper exhaust holes  32 A. In the present embodiment, the overlapped area of the second heat sink  43  and the second upper exhaust holes  32 A in the first direction D 1  is larger than the overlapped area of the first heat sink  41  and the first upper exhaust holes  31 A in the first direction D 1 . 
     The second heat sink  43  may face the second lower exhaust holes  32 B, in addition to the second upper exhaust holes  32 A or instead of the second upper exhaust holes  32 A. The first heat sink  41  may face only the first upper exhaust holes  31 A or only the first lower exhaust holes  31 B. 
     According to the electronic apparatus  1  having the above structure, heat release performance can be improved. 
     In recent years, electronic apparatuses have been thinner. Therefore, the size and thickness of fans and heat sinks need to be reduced. Thus, there is a possibility that cooling performance is insufficient. 
     The electronic apparatus  1  of the present embodiment comprises the first housing  2 , the heating component  40  housed in the first housing  2 , the first heat sink  41 , the first heat pipe  42  and the fan  45 . The first housing  2  comprises the first exhaust holes  31  and the second exhaust holes  32 . The first heat sink  41  faces the first exhaust holes  31 . The first heat pipe  42  thermally connects the heating component  40  and the first heat sink  41 . The fan  45  comprises the first discharge hole  51  which discharges airflow passing the first heat sink  41  and going to the first exhaust holes  31 , and the second discharge hole  52  which discharges airflow passing the circumference of the heating component  40  and going to the second exhaust holes  32 . 
     According to this structure, it is possible to increase the opening area of the discharge holes of the fan  45 , and increase the entire amount of discharged airflow as compared to a fan which has only one discharge hole and is the same in size. By using this increased airflow volume, airflow is discharged from the first discharge hole  51  to the first heat sink  41 , and further, airflow is discharged from the second discharge hole  52  directly to the heating component  40 . In this manner, it is possible to effectively promote cooling of the heating component  40 . Thus, the cooling performance of the electronic apparatus  1  can be enhanced. In addition, if the cooling performance of the electronic apparatus  1  is enhanced, the cooling device of the fan  45  and the heat sink  41 , etc. can be downsized. Thus, the size and the thickness of the electronic apparatus can be reduced. 
     Moreover, according to the above structure, the airflow which passed the first heat sink  41  is discharged from the first exhaust hole  31  to the outside of the first housing  2 . On the other hand, the airflow which passed the circumference of the heating component  40  is discharged from the second exhaust holes  32  to the outside of the first housing  2 . Therefore, even if either one of a group of first exhaust holes  31  and a group of second exhaust holes  32  is blocked for some reason, it is possible to promote cooling of the heating component  40  by discharging airflow from the other one of a group of first exhaust holes  31  and a group of second exhaust holes  32 . 
     In other words, for example, if the first exhaust holes  31  are blocked, the heating component  40  can be cooled down by the airflow which is discharged from the second discharge hole  52  of the fan  45 , passes the circumference of the heating component  40  and is discharged from the second exhaust holes  32 . For example, if the second exhaust holes  32  are blocked, the heating component  40  can be cooled down by the airflow which is discharged from the first exhaust hole  51  of the fan  45 , passes through the first heat sink and is discharged from the first exhaust holes  31 . Thus, the heat release of the heating component  40  is maintained. In this manner, the cooling performance of the electronic apparatus  1  can be stabilized. 
     In the present embodiment, the electronic apparatus  1  further comprise the second heat sink  43  facing the second exhaust holes  32 . The airflow from the second discharge hole  52  passes the circumference of the heating component  40 , passes through the second heat sink  43  and moves to the second exhaust holes  32 . According to this structure, by using the airflow directly blowing against the heating component  40 , the cooling performance of the electronic apparatus  1  can be further improved. 
     In the present embodiment, the electronic apparatus  1  further comprises the second heat pipe  44  which thermally connects the heating component  40  and the second heat sink  43 . According to this structure, by using the airflow directly blowing against the heating component  40 , the cooling of the heating component  40  can be further enhanced. This contributes to the improvement of the cooling performance of the electronic apparatus  1 . 
     In the present embodiment, the electronic apparatus  1  further comprises the second housing  3  rotatably attached to the first housing  2 . The first housing  2  comprises the first wall (e.g., the upper wall  11 ), the second wall (e.g., the lower wall  12 ) located on a side opposite to the first wall, and the third wall (e.g., the rear wall  17 ) which ranges over the first wall and the second wall and faces the second housing  3  when the second housing  3  is raised with respect to the first housing  2 . The first exhaust holes  31  and the second exhaust holes  32  are provided in the third wall, and face the second housing  3  standing relative to the first housing  2 . 
     For example, when an exhaust hole is provided in the rear wall of the first housing in a general electronic apparatus, the exhaust hole is covered by the second housing. Thus, through the reduction in the exhaust efficiency, the cooling performance might be reduced. However, in the electronic apparatus of the present embodiment, the number of exhaust holes is increased by the provision of the second exhaust holes  32  in addition to the first exhaust holes  31 . Therefore, even if the first exhaust holes  31  and the second exhaust holes  32  are covered by the second housing  3 , and thus exhaust efficiency of each hole is reduced, it is possible to ensure cooling efficiency sufficient to cool the electronic apparatus  1  in terms of the total exhaust amount of the first exhaust holes  31  and the second exhaust holes  32 . In this manner, the cooling performance of the electronic apparatus  1  can be improved. 
     A connector, etc. cannot be provided in the rear wall  17  of the first housing  2  since the second housing  3  faces the rear wall  17  when the second housing  3  is raised with respect to the first housing  2 . In the structure of the present embodiment, the number of exhaust holes is increased by utilizing the rear wall  17  of the first housing  2 . Generally, the rear wall  17  easily becomes dead space. Therefore, even if the number of exhaust holes is increased, it is possible to avoid enlarging the size of the electronic apparatus  1 . 
     In the present embodiment, the third wall comprises a portion (e.g., the outmost portion  60 ) located at the outermost position of the third wall in the direction from the fan  45  to the third wall, the first area  61  which inclines from the portion toward the first wall and extends, and the second area  62  which inclines from the portion toward the second wall. The first exhaust holes  31  include a portion located in one of the first area  61  and the second area  62 . The second exhaust holes  32  include a portion located in the other one of the first area  61  and the second area  62 . 
     According to this structure, even if the second housing  3  is at any opening state, exhaust holes on one side (i.e., the first exhaust holes  31  or the second exhaust holes  32 ) are always open. Therefore, even if the exhaust holes  31  and  32  are provided in the rear wall  17  of the first housing  2  covered by the second housing  3 , effective exhaust is possible, and thus, the cooling performance of the electronic apparatus  1  can be improved. 
     In the present embodiment, at the first opening angle of θ1, the second housing  3  faces the first and second upper exhaust holes  31 A and  32 A, and does not cover at least a part of the first and second lower exhaust holes  31 B and  32 B. Therefore, at the first opening angle of θ1, the airflow from the fan  45  can be effectively discharged from the first and second lower exhaust holes  31 B and  32 B. 
     In the present embodiment, at the second opening angle of θ2 which is larger than the first opening angle of θ1, the second housing  3  faces the first and second lower exhaust holes  31 B and  32 B. The gap g 2  between the second housing  3  and each of the first and second upper exhaust holes  31 A and  32 A is larger than the gap g 1  between the second housing  3  and each of the first and second upper exhaust holes  31 A and  32 A at the first opening angle of el. Therefore, at the second opening angle of θ 2 , the airflow from the fan  45  can be effectively discharged from the first and second upper exhaust holes  31 A and  32 A. 
     In the present embodiment, the first heat sink  41  and the second heat sink  43  are provided at positions shifted from each other along the rotation direction of the second housing  3  (or along the thickness direction of the first housing  2 ). According to this structure, even if one of the upper exhaust holes  31 A and  32 A and the lower exhaust holes  31 B and  32 B is covered by the second housing  3 , at least one of the first heat sink  41  and the second heat sink  43  effectively functions. Thus, it is possible to minimize the influence from the airflow amount reduction caused by the structure in which the second housing  3  covers the first exhaust holes  31  and the second exhaust holes  32 . In this manner, the cooling performance of the electronic apparatus  1  can be stabilized. 
     In the present embodiment, the second discharge hole  52  opens in a direction which is different from the first discharge hole  51 . The electronic apparatus  1  further comprises the guide  56  provided in the first housing  2 . The guide  56  guides airflow which was discharged from the second discharge hole  52  and passed the circumference of the heating component  40  so as to go to the second exhaust holes  32 . According to this structure, the airflow directly blowing against the heating component  40  can be effectively guided to the second exhaust holes  32 . Thus, the cooling performance of the electronic apparatus  1  can be further improved. 
     The second heat sink  43  may be unnecessary. The second heat sink  43  may be thermally connected to a heating component which is different from the heating component  40  thermally connected to the first heat sink  41 . 
     Next, the structure of the present embodiment is explained from another point of view. 
     For comparison, this specification now considers an electronic apparatus comprising a unidirectional exhaust fan in which an exhaust hole is provided in the rear wall of the first housing covered by the second housing, and airflow blows toward the exhaust hole. In this case, heat generated within the first housing  2  is mostly and intensively discharged from the above exhaust hole. 
     Therefore, a portion of the second housing faces the above exhaust hole and intensively receives heat. Thus, local elevation of temperature might arise in a part of the second housing. For example, on the condition that the electronic apparatus  1  of  FIG. 2  does not comprise the second exhaust holes  32 , the airflow from the fan  45  might intensively hit a first portion  71  of the second housing  3 , the first portion  71  facing the first exhaust holes  31 . Thus, the temperature of the first portion  71  might locally rise. This local elevation of temperature might have a bad influence on components housed in the second housing  3 . 
     On the other hand, the electronic apparatus  1  of the present embodiment comprises the first housing  2 , the second housing  3 , the first heat sink  41 , the heating component  40  housed in the first housing  2 , and the fan  45 . The first housing  2  comprises the first exhaust holes  31  and the second exhaust holes  32 . The second housing  3  is rotatably attached to the first housing  2 , and faces the first exhaust holes  31  and the second exhaust holes  32  when the second housing  3  stands relative to the first housing  2 . The first heat sink  41  faces the first exhaust holes  31 . The fan  45  comprises the first discharge hole  51  configured to discharge airflow which passes the first heat sink  41  and goes to the first exhaust holes  31 . The fan  45  further comprises the second discharge hole  52  configured to discharge airflow which passes the circumference of the heating component  40  and goes to the second exhaust holes  32 . 
     According to this structure, the airflow which was discharged from the first discharge hole  51  and took heat from the heat sink  41  is discharged from the first exhaust holes  31  and hits the first portion  71  of the second housing  3 , the first portion  71  facing the first exhaust holes  31 . On the other hand, the airflow which was discharged from the second discharge hole  52  and directly took heat from the heating component  40  is discharged from the second exhaust holes  32 , and hits a second portion  72  of the second housing  3 , the first portion  71  facing the second exhaust holes  32 . Thus, the heat generated within the first housing  2  separately has an influence on the first portion  71  and the second portion  72  of the second housing  3 . Therefore, it is possible to avoid local elevation of temperature within the second housing  3 , and equalize the heat within the second housing  3 . In this manner, the cooling performance of the electronic apparatus  1  can be improved. Further, the reliability and lifetime of the electronic apparatus  1  can be improved. 
     In particular, when the first heat sink  41  is connected to the heating component  40 , the heat from the heating component  40  can be divided into the first portion  71  and the second portion  72  of the second housing  3 . Therefore, the equalization of heat of the second housing  3  can be further improved. 
     In a case of this point of view, the first heat sink  41  may not be thermally connected to the heating component  40 . For example, as shown in  FIG. 9 , the first heat sink  41  may be thermally connected to a heating component  75  which is different from the heating component  40 . 
     In the present embodiment, the electronic apparatus  1  further comprises the second heat sink  43  facing the second exhaust holes  32 . The airflow from the second discharge hole  52  passes the circumference of the heating component  40 , and then goes through the second heat sink  43  to the second exhaust holes  32 . According to this structure, the heat from the first heat sink  41  and the heat from the second heat sink  43  can be divided into the first portion  71  and the second portion  72  of the second housing  3 . Thus, the equalization of heat of the second housing  3  can be further improved. 
     Next, the structure of the present embodiment is explained from another point of view. 
     The electronic apparatus  1  of the present embodiment comprises the first housing  2 , the second housing  3 , the first heat sink  41 , the heating component  40  housed in the first housing  2 , the second heat sink  43  and the fan  45 . The first housing  2  comprises the first exhaust holes  31  and the second exhaust holes  32 . The second housing  3  is rotatably attached to the first housing  2 , and faces the first holes  31  and the second exhaust holes  32  when the second housing  3  is raised with respect to the first housing  2 . The first heat sink  41  faces the first exhaust holes  31 . The second heat sink  43  is thermally connected to the heating component  40 . The fan  45  comprises the first discharge hole  51  configured to discharge airflow which goes through the first heat sink  41  to the first exhaust holes  31 , and the second discharge hole  52  configured to discharge airflow which goes through the second heat sink  43  to the second exhaust holes  32 . 
     According to this structure, the heat from the first heat sink  41  and the heat from the second heat sink  43  can be divided into the first portion  71  and the second portion  72  of the second housing  3 . Therefore, the equalization of heat of the second housing  3  can be improved. In this manner, the cooling performance of the electronic apparatus  1  can be enhanced, and the reliability and lifetime of the electronic apparatus  1  can be improved. 
     In a case of this point of view, the first heat sink  41  may not be thermally connected to the heating component  40 . As shown in  FIG. 9 , the first heat sink  41  may be thermally connected to the heating component  75  which is different from the heating component  40 . The heating component  40  may not be directly cooled down by the airflow from the second discharge hole  52 . The heating component  40  may be provided so as not to directly receive the airflow from the second discharge hole  52 . 
     Next, with reference to  FIG. 10 , a modification of the first exhaust holes  31  and the second exhaust holes  32  are explained. As shown in  FIG. 10 , each of the first exhaust holes  31  and the second exhaust holes  32  may range from the first area  61  to the second area  62  in the rear wall  17 . In other words, each of the first upper exhaust holes  31 A and a corresponding first lower exhaust hole  31 B may be connected to each other to be formed as one hole. Similarly, each of the second upper exhaust holes  32 A and a corresponding second lower exhaust hole  32 B may be connected to each other to be formed as one hole. This modification is applicable to the electronic apparatus  1  of all of the standpoints described above. 
     Next, a modification of the fan  45  is explained with reference to  FIG. 11  and  FIG. 12 . As shown in  FIG. 11 , the first discharge hole  51  is provided in substantially the whole area of the first lateral surface  47   a  of the fan case  47 . On the other hand, as shown in  FIG. 12 , the second discharge hole  52  is provided in a part (e.g., the upper half portion) of the second lateral surface  47   b  of the fan case  47  in such a way that the second discharge hole  52  faces only the space above the circuit board  5 . 
     According to this structure, it is possible to effectively send airflow from the second discharge hole  52  to the heating component  40 , and thus, the cooling performance of the electronic apparatus  1  can be improved. This modification is applicable to the electronic apparatus  1  of all of the standpoints described above. 
     In the above descriptions, one embodiment and its modifications are explained. However, the present invention is not limited to the embodiment and modifications. The structures related to the above embodiment and modifications can be implemented by appropriate modification, exchange or combination. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.