Patent Publication Number: US-2009231809-A1

Title: Electronic Apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2008-062581, filed on Mar. 12, 2008, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     An aspect of the present invention relates to an electronic apparatus in which air volumes exhausted from each of air exhaust ports of a bidirectional air exhaust fan are dynamically controlled to cool heat generating components. 
     2. Description of the Related Art 
     Recently, with sophistication of an electronic apparatus, a plurality of CPU boards and a fan are mounted on the electronic apparatus. Irrespective of different generated heat amounts of the CPU boards, the fan blows only a constant air volume, and hence a temperature difference is produced among the CPU boards. Therefore, operation margins of the CPU boards are different from each other, and there may arise a problem in that operation reliabilities are lowered. 
     An electronic apparatus has been proposed in which the air volume is adjusted in accordance with the change of the generated heat amount, whereby the cooling efficiency is improved and the temperature differences among boards and LSIs in the apparatus are reduced (see JP-A-2005-286268, for instance). In the electronic apparatus, air exhaust ports are disposed for each of heat generating components, and air volumes blown to the heat generating components are independently controlled. 
     In the case where a bidirectional air exhaust fan is used as an air exhaust fan, usually the air volumes blown to air exhaust ports are not equal to each other, and there is a tendency of “air volume blown to a first exhaust port&gt;air volume blown to a second exhaust port”. Even in the case where a temperature of a heat generating component cooled at the second exhaust port is higher than that of a heat generating component cooled at the first exhaust port, a larger air volume is exhausted to the first exhaust port which is not required to perform further cooling, and hence it is necessary to increase the number of rotations of the bidirectional air exhaust fan more than necessary. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       A general architecture that implements the various feature of the present invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the present invention and not to limit the scope of the present invention. 
         FIG. 1  is an exemplary perspective view of an electronic apparatus of a first embodiment of the invention; 
         FIG. 2  is an exemplary block diagram showing the electronic apparatus of the first embodiment; 
         FIG. 3  is an exemplary diagram showing a cooling mechanism in the first embodiment; 
         FIG. 4  is an exemplary flowchart showing a procedure in the case where the electronic apparatus of the first embodiment performs an air exhaust control process; 
         FIG. 5  is an exemplary diagram illustrating the air exhaust control process in the electronic apparatus of the first embodiment; 
         FIG. 6  is an exemplary diagram illustrating the air exhaust control process in the electronic apparatus of the first embodiment; 
         FIG. 7  is an exemplary diagram illustrating the air exhaust control process in the electronic apparatus of the first embodiment; 
         FIG. 8  is an exemplary diagram illustrating the air exhaust control process in the electronic apparatus of the first embodiment; 
         FIG. 9  is an exemplary diagram illustrating the air exhaust control process in the electronic apparatus of the first embodiment; 
         FIG. 10  is an exemplary flowchart showing the procedure in the case where the electronic apparatus of the first embodiment performs the air exhaust control process; 
         FIG. 11  is an exemplary block diagram showing an electronic apparatus of a second embodiment of the invention; 
         FIG. 12  is an exemplary diagram showing a cooling mechanism in the second embodiment; 
         FIG. 13  is an exemplary flowchart showing the procedure in the case where the electronic apparatus of the second embodiment performs an air exhaust control process; 
         FIG. 14  is an exemplary diagram illustrating the air exhaust control process in the electronic apparatus of the second embodiment; 
         FIG. 15  is an exemplary diagram illustrating the air exhaust control process in the electronic apparatus of the second embodiment; 
         FIG. 16  is an exemplary diagram illustrating the air exhaust control process in the electronic apparatus of the second embodiment; 
         FIG. 17  is an exemplary diagram illustrating the air exhaust control process in the electronic apparatus of the second embodiment; 
         FIG. 18  is an exemplary diagram illustrating the air exhaust control process in the electronic apparatus of the second embodiment; and 
         FIG. 19  is an exemplary flowchart showing the procedure in the case where the electronic apparatus of the second embodiment performs the air exhaust control process. 
     
    
    
     DETAILED DESCRIPTION  
     Various embodiments according to the present invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the present invention, an electronic apparatus includes: a plurality of heat generating components; a plurality of heat sinks respectively provided for the plurality of heat generating components; a fan that simultaneously blows air to the heat sinks; a plurality of shutters that respectively block air flows blown from the fan to the heat sinks; a determining section configured to, based on temperatures of the heat generating components, determine whether one of the heat generating components needs to be cooled or not; and a controlling section configured to operate at least one of the shutters to control air volume blown over one of the heat sinks that corresponds to the one of the heat generating components that needs to be cooled. 
     First Embodiment 
     A first embodiment of an electronic apparatus of the invention will be described with reference to  FIGS. 1 to 10 .  FIG. 1  is a perspective view of the electronic apparatus  1  of the invention. The electronic apparatus  1  is a notebook Personal Computer (PC) which is usually used, or the like. In the electronic apparatus  1 , as shown in  FIG. 1 , a keyboard  2  having a plurality of keys which are depressed when the user inputs instructions, a display device  3  which displays a screen showing characters, images, and the like, and a speaker  4  which outputs sounds are disposed so as to be exposed to the outside. 
       FIG. 2  is a block diagram of the electronic apparatus  1 . As shown in  FIG. 2 , the electronic apparatus  1  includes a Central Processing Unit (CPU)  11 , a Random Access Memory (RAM)  12 , a Hard Disk (HD) drive  13 , a Read Only Memory (ROM) drive  14 , a GPU  15 , an audio codec  16 , and an air exhaust controlling circuit  17 . These components are interconnected by a chip set  18 . 
     The CPU  11  generally controls the electronic apparatus  1 , and performs a drawing control process which will be described later, and other various calculation and control processes. The CPU  11  includes input interfaces for input devices such as the keyboard  2  and a mouse which is externally connected, and performs various processes based on a signal input through the input devices. The RAM  12  is used as a working area when the CPU  11  performs a process, and temporarily stores data required in the process. 
     The HD drive  13  is a driving device for applying writing and reading operations on a Hard Disk (HD) which stores process program required in processes to be performed by the CPU  11 , and data necessary for the processes. The ROM drive  14  is a driving device for applying writing and reading operations on a recording medium such as a Digital Versatile 
     The GPU  15  includes a video RAM which temporarily stores character or graphic data to be displayed on the display device  3 , and which is used in a process of two-dimensional graphics (2D) or three-dimensional graphics (3D) or a motion picture process, and, under the control of the CPU  11 , outputs frame data loaded in the video RAM to the display device  3 . 
     The audio codec  16  includes an output interface which causes the speaker  4  disposed on the electronic apparatus  1  to output a sound, and, under the control of the CPU  11 , converts a digital audio signal to an analog signal, and then outputs it as a sound from the speaker  4 . 
     The air exhaust controlling circuit  17  controls a cooling mechanism  20  which cools heat generating components a, b such as the CPU  11  and the CPU  15 . Specifically, the air exhaust controlling circuit  17  obtains the temperatures of the heat generating components a, b, determines whether the heat generating components are to be cooled or not, and, if it is determined that the heat generating components are to be cooled, performs an air exhaust control process of cooling the heat generating components a, b. 
     The chip set  18  is an integrated circuit including a memory controller, a bus bridge, an Integrated Drive Electronics (IDE) controller, various I/O controllers, etc. 
     The cooling mechanism  20  is a mechanism which, under the control of the air exhaust controlling circuit  17 , cools the heat generating components a, b such as the CPU  11  and the GPU  15 . As shown in  FIG. 3 , the cooling mechanism  20  includes heat sinks  21 ,  21   a  for the heat generating components a, b, respectively. The heat generating components a, b are cooled by the heat sinks  21 ,  21   a,  respectively. The heat sink  21  is provided with an air exhaust port (A)  22  to blow hot air to the outside, and similarly the heat sink  21   a  is provided with an air exhaust port (B)  22   a.  The cooling mechanism  20  further includes a bidirectional air exhaust fan  23 , so that the air blown by the bidirectional air exhaust fan  23  is passed over the heat sink  21  or the heat sink  21   a  and then exhausted from the respective air exhaust ports  22 ,  22   a.    
     A blocking shutter  24  is disposed between the bidirectional air exhaust fan  23  and the heat sink  21 , and a blocking shutter  24   a  is disposed between the bidirectional air exhaust fan  23  and the heat sink  21   a.  The blocking shutters  24 ,  24   a  are shutters in which the aperture ratio is changeable in order to control the air volume blown from the bidirectional air exhaust fan  23  to the corresponding heat sink  21  or  21   a.  In this example, it is assumed that the blocking shutters  24 ,  24   a  are changeable to either of three states or an aperture ratio of 0% (a completely closed state), an aperture ratio of 50% (a state where the blocking shutter is half-opened), and an aperture ratio of 100% (a state where the blocking shutter is opened). 
     The cooling mechanism  20  includes temperature sensors  25 ,  25   a  in vicinities of the heat generating components a, b such as the CPU  11  and the GPU  15 , respectively. The air exhaust controlling circuit  17  obtains the temperature of the heat generating component a (the CPU  11 ) from the temperature sensor  25 , and also that of the heat generating component b (the CPU  15 ) from the temperature sensor  25   a.  The temperature sensors  25 ,  25   a  may be incorporated in the CPU  11  and the GPU  15 . Based on the temperatures, the air exhaust controlling circuit  17  adjusts the aperture ratios of the blocking shutters  24 ,  24   a,  or the number of rotations of the bidirectional air exhaust fan  23 , whereby the heat generating components a, b are cooled while the exhaust air volumes to the heat sinks  21 ,  21   a  are controlled. 
     The air exhaust controlling circuit  17  of the electronic apparatus  1  obtains the temperatures of the heat generating components a, b such as the CPU  11  and the CPU  15 , at, for example, regular intervals, and, based on the temperatures, performs the air exhaust control process in which the aperture ratios of the blocking shutters  24 ,  24   a  are adjusted, or the air volume of the bidirectional air exhaust fan  23  is adjusted. The procedure in which the electronic apparatus  1  performs the air exhaust control process will be described with reference to the flowcharts shown in  FIGS. 4 and 10 . Hereinafter, the description will be made while the term “step” is omitted so that, for example, “step S 101 ” is referred to as “S 101 ”. 
     Here, it is assumed that, when both the blocking shutter  24  on the side of the air exhaust port (A)  22 , and the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  are opened, an air flow of 60% volume of an air flow generated by the bidirectional air exhaust fan  23  flows to the air exhaust port (A)  22 , and an air flow of 40% flows to the air exhaust port (B)  22   a  as shown in  FIG. 7 . 
     First, the air exhaust controlling circuit  17  determines whether the temperature of the heat generating component b (the CPU  15 ) is higher than that of the heat generating component a (the CPU  11 ) or not (S 101 ). This determination is performed by the air exhaust controlling circuit  17  with obtaining the temperatures of the CPU  11  and the CPU  15  from the temperature sensors  25 ,  25   a,  and comparing the temperatures. 
     The case where the temperature of the heat generating component b (the GPU  15 ) is higher than that of the heat generating component a (the CPU  11 ) will be described with reference to the flowchart shown in  FIG. 4 . If the temperature of the heat generating component b is higher than that of the heat generating component a (Yes in S 101 ), the air exhaust controlling circuit  17  determines whether it is necessary to increase the air volume in order to cool the heat generating component b or not (S 103 ). In the case where the temperature of the heat generating component b is equal to or higher than a threshold value, for example, it is determined that the air volume is necessary to be increased. 
     If it is not necessary to increase the air volume for cooling the heat generating component b (No in S 103 ), it is not necessary to cool the heat generating component a in which the temperature is lower than the heat generating component b, and hence the process returns to step S 101  in which the air exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If it is necessary to increase the air volume for cooling the heat generating component b (Yes in S 103 ), the air exhaust controlling circuit  17  determines whether the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is 0% as shown in  FIG. 5  or not, i.e., whether the blocking shutter  24   a  is completely closed or not, in order to seek means for cooling the heat generating component b without increasing the number of rotations of the bidirectional air exhaust fan  23  (S 105 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  does not flow to the air exhaust port (B)  22   a  by the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a,  and hence an air flow of an air volume of 100% flows to the air exhaust port (A)  22 . 
     If the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is 0% (Yes in S 105 ), the air exhaust controlling circuit  17  adjusts the aperture ratio of the blocking shutter  24   a  to 50% (S 107 ). As a result, as shown in  FIG. 6 , an air flow of an air volume of 80% flows to the air exhaust port (A)  22 , and an air flow of 20% flows to the air exhaust port (B)  22   a.  In this way, when the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is increased, an air flow of a larger air volume can be supplied to the heat sink  21   a  on the side of the heat generating component b (the GPU  15 ), and the heat generating component b can be cooled. Then, the process returns to step S 101  in which the air exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is not 0% (No in S 105 ), the air exhaust controlling circuit  17  determines whether the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is 50% as shown in  FIG. 6  or not (S 109 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  hardly flows to the air exhaust port (B)  22   a  by the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a.  Therefore, an air flow of an air volume of 80% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 20% flows to the air exhaust port (B). 
     If the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is 50% (Yes in S 109 ), the air exhaust controlling circuit  17  opens the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a,  i.e., adjusts the aperture ratio to 100% (S 111 ). As a result, as shown in  FIG. 7 , an air flow of an air volume of 60% flows to the air exhaust port (A)  22 , and an air flow of 40% flows to the air exhaust port (B)  22   a.  In this way, when the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is completely opened, an air flow of a larger air volume can be supplied to the heat sink  21   a  on the side of the heat generating component b (the GPU  15 ), and the heat generating component b can be cooled. Then, the process returns to step S 101  in which the air exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is not 50% (No in S 109 ), the air exhaust controlling circuit  17  determines whether the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is 100% as shown in  FIG. 7  or not, i.e., whether the blocking shutter  24  is opened or not (S 113 ). In this case, an air flow of an air volume of 60% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 40% flows to the air exhaust port (B)  22   a.    
     If the blocking shutter  24  on the side of the air exhaust port (A)  22  is opened (Yes in S 113 ), the air exhaust controlling circuit  17  adjusts the aperture ratio of the blocking shutter  24  to 50% (S 115 ). As a result, as shown in  FIG. 8 , an air flow of an air volume of 30% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 70% flows to the air exhaust port (B)  22   a.  In this way, when the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is decreased to restrict the air volume blown to the air exhaust port (A)  22 , an air flow of a larger air volume can be supplied to the heat sink  21   a  on the side of the heat generating component b (the GPU  15 ), and the heat generating component b can be cooled. Then, the process returns to step S 101  in which the air exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the blocking shutter  24  on the side of the air exhaust port (A)  22  is not opened (No in S 113 ), the air exhaust controlling circuit  17  determines whether the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is 50% as shown in  FIG. 8  or not (S 117 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  hardly flows to the air exhaust port (A)  22  by the blocking shutter  24  on the side of the air exhaust port (A)  22 . Therefore, an air flow of an air volume of 30% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 70% flows to the air exhaust port (B)  22   a.    
     If the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is 50% (Yes in S 117 ), the air exhaust controlling circuit  17  adjusts the aperture ratio of the blocking shutter  24  to 0% (S 119 ). As a result, as shown in  FIG. 9 , an air flow of an air volume of 0% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 100% flows to the air exhaust port (B)  22   a.  In this way, when the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is decreased and the air flow to the air exhaust port (A)  22  is blocked, an air flow of a larger air volume can be supplied to the heat sink  21   a  on the side of the heat generating component b (the GPU  15 ), and the heat generating component b can be cooled. Then, the process returns to step S 101  in which the air exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is not 50%, i.e., if the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is 0% as shown in  FIG. 9  (No in S 117 ), the heat generating component b cannot be cooled simply by controlling the blocking shutters  24 ,  24   a,  and hence the air exhaust controlling circuit  17  increases the number of rotations of the bidirectional air exhaust fan  23  (S 121 ). When the number of rotations of the bidirectional air exhaust fan  23  is increased, an air flow of a larger air volume can be supplied to the heat sink  21   a  for the heat generating component b (the GPU  15 ), and the heat generating component b can be cooled. Then, the process returns to step S 101  in which the air exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     In the case where it is necessary to cool the heat generating component b, if the heat generating component b can be cooled by adjusting the aperture ratios or operating the blocking shutters  24 ,  24   a,  the electronic apparatus  1  adjusts the aperture ratios or operating the blocking shutters  24 ,  24   a  to cool the heat generating component b. If not, the heat generating component b is cooled by increasing the number of rotations of the bidirectional air exhaust fan  23 . 
     Next, the case where the temperature of the heat generating component a (the CPU  11 ) is higher than that of the heat generating component b (the GPU  15 ) will be described with reference to the flowchart shown in  FIG. 10 . If the temperature of the heat generating component a (the CPU  11 ) is higher than that of the heat generating component b (the GPU  15 ) (No in S 101 ), the air exhaust controlling circuit  17  determines whether it is necessary to increase the air volume for cooling the heat generating component a or not (S 201 ). In the case where the temperature of the heat generating component b is equal to or higher than a threshold value, for example, it is determined that an increase of the air volume is necessary. 
     If it is not necessary to increase the air volume for cooling the heat generating component a (No in S 201 ), it is not necessary to cool the heat generating component b in which the temperature is lower than the heat generating component a, and hence the process returns to step S 101  in which the air exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If it is necessary to increase the air volume for cooling the heat generating component a (Yes in S 201 ), the air exhaust controlling circuit  17  determines whether the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is 0% as shown in  FIG. 9  or not, i.e., whether the blocking shutter  24  is completely closed or not, in order to seek means for cooling the heat generating component a without increasing the number of rotations of the bidirectional air exhaust fan  23  (S 203 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  does not flow to the air exhaust port (A)  22  by the blocking shutter  24  on the side of the air exhaust port (A)  22 , and hence an air flow of an air volume of 100% flows to the air exhaust port (B)  22   a.    
     If the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is 0% (Yes in S 203 ), the air exhaust controlling circuit  17  adjusts the aperture ratio of the blocking shutter  24  to 50% (S 205 ). As a result, as shown in  FIG. 8 , an air flow of 30% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 70% flows to the air exhaust port (B)  22   a.  In this way, when the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is increased, an air flow of a larger air volume can be supplied to the heat sink  21  on the side of the heat generating component a (the CPU  11 ), and the heat generating component a can be cooled. Then, the process returns to step S 101  in which the air exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is not 0% (No in S 203 ), the air exhaust controlling circuit  17  determines whether the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is 50% as shown in  FIG. 8  or not (S 207 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  hardly flows to the air exhaust port (A)  22  by the blocking shutter  24  on the side of the air exhaust port (A)  22 . Therefore, an air flow of an air volume of 30% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 70% flows to the air exhaust port (B)  22   a.    
     If the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is 50% (Yes in S 207 ), the air exhaust controlling circuit  17  opens the blocking shutter  24 , i.e., adjusts the aperture ratio to 100% (S 209 ). As a result, as shown in  FIG. 7 , an air flow of an air volume of 60% flows to the air exhaust port (A), and an air flow of 40% flows to the air exhaust port (B). In this way, when the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is completely opened, an air flow of a larger air volume can be supplied to the heat sink  21  on the side of the heat generating component a (the CPU  11 ), and the heat generating component a can be cooled. Then, the process returns to step S 101  in which the air exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the aperture ratio of the blocking shutter  24  on the side of the air exhaust port (A)  22  is not 50% (No in S 207 ), the air exhaust controlling circuit  17  determines whether the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is 100% as shown in  FIG. 7  or not, i.e., whether the blocking shutter  24  is opened or not (S 211 ). In this case, an air flow of an air volume of 60% flows to the air exhaust port (A), and an air flow of an air volume of 40% flows to the air exhaust port (B). 
     If the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is opened (Yes in S 211 ), the air exhaust controlling circuit  17  adjusts the aperture ratio of the blocking shutter  24   a  to 50% (S 213 ). As a result, as shown in  FIG. 6 , an air flow of an air volume of 80% flows to the air exhaust port (A), and an air flow of an air volume of 20% flows to the air exhaust port (B). In this way, when the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is decreased to restrict the air volume blown to the air exhaust port (B)  22   a,  an air flow of a larger air volume can be supplied to the heat sink  21  on the side of the heat generating component a (the CPU  11 ), and the heat generating component a can be cooled. Then, the process returns to step S 101  in which the air exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is not opened (No in S 211 ), the air exhaust controlling circuit  17  determines whether the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is 50% as shown in  FIG. 6  or not (S 215 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  hardly flows to the air exhaust port (B)  22   a  by the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a.  Therefore, an air flow of an air volume of 80% flows to the air exhaust port (A), and an air flow of an air volume of 20% flows to the air exhaust port (B). 
     If the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is 50% (Yes in S 215 ), the air exhaust controlling circuit  17  adjusts the aperture ratio of the blocking shutter  24   a  to 0% (S 217 ). As a result, as shown in  FIG. 5 , an air flow of an air volume of 100% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 0% flows to the air exhaust port (B)  22   a.  In this way, when the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is completely closed and the air flow to the air exhaust port (B)  22   a  is blocked, an air flow of a larger air volume can be supplied to the heat sink  21  on the side of the heat generating component a (the CPU  11 ), and the heat generating component a can be cooled. Then, the process returns to step S 101  in which the air -  20  - exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is not 50%, i.e., if the aperture ratio of the blocking shutter  24   a  on the side of the air exhaust port (B)  22   a  is 0% as shown in  FIG. 5  (No in S 215 ), the heat generating component a cannot be cooled simply by controlling the blocking shutters  24 ,  24   a,  and hence the air exhaust controlling circuit  17  increases the number of rotations of the bidirectional air exhaust fan  23  (S 219 ). When the number of rotations of the bidirectional air exhaust fan  23  is increased, an air flow of a larger air volume can be supplied to the heat sink  21  on the side of the heat generating component a (the CPU  11 ), and the heat generating component a can be cooled. Then, the process returns to step S 101  in which the air exhaust controlling circuit  17  again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     In the case where it is necessary to cool the heat generating component a, if the heat generating component a can be cooled by adjusting the aperture ratios or operating the blocking shutters  24 ,  24   a,  the electronic apparatus  1  adjusts the aperture ratios or operates the blocking shutters  24 ,  24   a  to cool the heat generating component a. If not, the heat generating component a is cooled by increasing the number of rotations of the bidirectional air exhaust fan  23 . 
     According to the first embodiment, the exhaust air volumes of the air exhaust ports  22 ,  22   a  of the bidirectional air exhaust fan  23  are dynamically controlled based on the temperatures of the heat generating components a, b to suppress unnecessary air exhaust and enhance the cooling efficiency, whereby the number of rotations of the air exhaust fan  23  can be maintained to an optimum state and the heat generating components a, b can be cooled. 
     Second Embodiment 
     A second embodiment of the electronic apparatus of the invention will be described with reference to  FIGS. 11 to 19 . The components identical with those of the first embodiment are denoted by the same reference numerals, and duplicate description will be omitted. In the same manner as the electronic apparatus  1  of the first embodiment, the electronic apparatus  1 A of the second embodiment is a notebook Personal Computer (PC) which is usually used, or the like. In the electronic apparatus  1 A, as shown in  FIG. 1 , the keyboard  2  having a plurality of keys which are depressed when the user inputs instructions, the display device  3  which displays a screen showing characters, images, and the like, and the speaker  4  which outputs sounds are disposed so as to be exposed to the outside. 
       FIG. 11  is a block diagram of the electronic apparatus  1 A. As shown in  FIG. 11 , the electronic apparatus  1 A includes a Central Processing Unit (CPU)  11 , a Random Access Memory (PAM)  12 , a Hard Disk (HD) drive  13 , a Read Only Memory (ROM) drive  14 , a GPU  15 , an audio codec  16 , and an air exhaust controlling circuit  17 A which controls a cooling mechanism  20 A for the CPU  11  and the GPU  15 . These components are interconnected by a chip set  18 . 
     The air exhaust controlling circuit  17 A controls a cooling mechanism  20 A which cools heat generating components a, b such as the CPU  11  and the GPU  15 . Specifically, the air exhaust controlling circuit  17 A obtains the temperatures of the heat generating components a, b such as the CPU  11  and the CPU  15 , and determines whether the heat generating components a, b are to be cooled or not, and, if it is determined that the heat generating components are to be cooled, performs an air exhaust control process of cooling the heat generating components a, b. 
     As shown in  FIG. 12 , the cooling mechanism  20 A is a mechanism which, under the control of the air exhaust controlling circuit  17 A, cools the heat generating components a, b such as the CPU  11  and the GPU  15 . As shown in  FIG. 12 , the cooling mechanism  20 A includes heat sinks  21 ,  21   a  for the heat generating components a, b, respectively. The heat generating components a, b are cooled by the heat sinks  21 ,  21   a,  respectively. The heat sink  21  is provided with an air exhaust port (A)  22  to blow hot air to the outside, and similarly the heat sink  21   a  is provided with an air exhaust port (B)  22   a.  The cooling mechanism  20 A further includes a bidirectional air exhaust fan  23 , so that the air blown by the bidirectional air exhaust fan  23  is passed over the heat sink  21  or the heat sink  21   a  and then exhausted from the respective air exhaust ports  22 ,  22   a.    
     A blocking shutter  26  and an air volume suppressing filter  27  are disposed between the bidirectional air exhaust fan  23  and the heat sink  21 , and a blocking shutter  26   a  and an air volume suppressing filter  27   a  are disposed between the bidirectional air exhaust fan  23  and the heat sink  21   a.  The blocking shutters  26 ,  26   a  are shutters which block the air flow blown from the bidirectional air exhaust fan  23 , from flowing to the corresponding heat sink  21  or  21   a.  It is assumed that the blocking shutters  26 ,  26   a  can block 100% of the air volume. 
     The air volume suppressing filters  27 ,  27   a  are filters which suppress the air volume that is generated by the bidirectional air exhaust fan  23 , and that flows to the corresponding heat sink  21  or  21   a.  A fine filter element is used in the air volume suppressing filters  27 ,  27   a  to increase the airflow resistance, whereby the air volume is suppressed. When the air volume suppressing filter  27  is placed on the side of the air exhaust port (A)  22 , for example, the airflow resistance is made larger, and the wind pressure on the side of the air exhaust port (B)  22   a  is increased, with the result that the exhaust air volume on the side of the air exhaust port (B)  22   a  can be increased. Here, it is assumed that the air volume suppressing filters  27 ,  27   a  can suppress the air volume to 50%. 
     The cooling mechanism  20 A includes temperature sensors  25 ,  25   a  in the vicinities of the heat generating components a, b such as the CPU  11  and the CPU  15 , respectively. The air exhaust controlling circuit  17 A obtains the temperature of the heat generating component a (the CPU  11 ) from the temperature sensor  25 , and also that of the heat generating component b (the GPU  15 ) from the temperature sensor  25   a.  The temperature sensors  25 ,  25   a  may be incorporated in the heat generating components a, b such as the CPU  11  and the GPU  15 . Based on the temperatures, the air exhaust controlling circuit  17 A adjusts the set states of the blocking shutters  26 ,  26   a  and the air volume suppressing filters  27 ,  27   a,  or the number of rotations of the bidirectional air exhaust fan  23 , whereby the heat generating components a, b are cooled while the exhaust air volumes to the heat sinks  21 ,  21   a  are adjusted. 
     The electronic apparatus  1 A obtains the temperatures of the heat generating components a, b such as the CPU  11  and the GPU  15 , at, for example, regular intervals, and, based on the temperatures, performs the air exhaust control process in which the set states of the blocking shutters  26 ,  26   a  and the air volume suppressing filters  27 ,  27   a  are adjusted, or the air volume of the bidirectional air exhaust fan  23  is adjusted. The procedure in which the electronic apparatus  1 A performs the air exhaust control process will be described with reference to the flowcharts shown in  FIGS. 13 and 19 . 
     Here, it is assumed that, when all of the blocking shutter  26  and the air volume suppressing filter  27  on the side of the air exhaust port (A)  22 , and the blocking shutter  26   a  and the air volume suppressing filter  27   a  on the side of the air exhaust port (B)  22   a  are opened, an air flow of an air volume of 60% of an air flow generated by the bidirectional air exhaust fan  23  flows to the air exhaust port (A)  22 , and an air flow of an air volume of 40% flows to the air exhaust port (B)  22   a  as shown in  FIG. 16 . 
     First, the air exhaust controlling circuit  17 A determines whether the temperature of the heat generating component b (the GPU  15 ) is higher than that of the heat generating component a (the CPU  11 ) or not (S 301 ). This determination is performed by the air exhaust controlling circuit  17 A with obtaining the temperatures of the CPU  11  and the GPU  15  from the temperature sensors  25 ,  25   a,  and comparing the temperatures. 
     The case where the temperature of the heat generating component b (the CPU  15 ) is higher than that of the heat generating component a (the CPU  11 ) will be described with reference to the flowchart shown in  FIG. 13 . If the temperature of the heat generating component b is higher than that of the heat generating component a (Yes in S 301 ), the air exhaust controlling circuit  17 A determines whether it is necessary to increase the air volume in order to cool the heat generating component b or not (S 303 ). In the case where the temperature of the heat generating component b is equal to or higher than a threshold value, for example, it is determined that the air volume is necessary to be increased. 
     If it is not necessary to increase the air volume for cooling the heat generating component b (No in S 303 ), it is not necessary to cool the heat generating component a in which the temperature is lower than the heat generating component b, and hence the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If it is necessary to increase the air volume for cooling the heat generating component b (Yes in S 303 ), the air exhaust controlling circuit  17 A determines whether the aperture ratio of the blocking shutter  26   a  on the side of the air exhaust port (B)  22   a  is 0% as shown in  FIG. 14  or not, i.e., whether the blocking shutter  26   a  is completely closed or not, in order to seek means for cooling the heat generating component b without increasing the number of rotations of the bidirectional air exhaust fan  23  (S 305 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  does not flow to the air exhaust port (B)  22   a  by the blocking shutter  26   a  on the side of the air exhaust port (B)  22   a,  and hence an air flow of an air volume of 100% flows to the air exhaust port (A)  22 . 
     If the blocking shutter  26   a  on the side of the air exhaust port (B)  22   a  is closed (Yes in S 305 ), the air exhaust controlling circuit  17 A opens the blocking shutter  26   a  (S 307 ). As a result, as shown in  FIG. 15 , an air flow of an air volume of 80% flows to the air exhaust port (A)  22 , and an air flow of 20% flows to the air exhaust port (B)  22   a.  In this way, when the blocking shutter  26   a  on the side of the air exhaust port (B)  22   a  is opened, an air flow of a larger air volume can be supplied to the heat sink  21   a  on the side of the heat generating component b (the GPU  15 ), and the heat generating component b can be cooled. Then, the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the blocking shutter  26   a  on the side of the air exhaust port (B)  22   a  is not closed (No in  5305 ), the air exhaust controlling circuit  17 A determines whether the air volume suppressing filter  27   a  on the side of the air exhaust port (B)  22   a  is closed as shown in  FIG. 15  or not (S 309 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  hardly flows to the air exhaust port (B)  22   a  by the air volume suppressing filter  27   a  on the side of the air exhaust port (B)  22   a.  Therefore, an air flow of an air volume of 80% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 20% flows to the air exhaust port (B). 
     If the air volume suppressing filter  27   a  on the side of the air exhaust port (B)  22   a  is closed (Yes in S 309 ), the air exhaust controlling circuit  17 A opens the air volume suppressing filter  27   a  (S 311 ). As a result, as shown in  FIG. 16 , an air flow of an air volume of 60% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 40% flows to the air exhaust port (B)  22   a.  In this way, when the air volume suppressing filter  27   a  on the side of the air exhaust port (B)  22   a  is completely opened, an air flow of a larger air volume can be supplied to the heat sink  21   a  on the side of the heat generating component b (the GPU  15 ), and the heat generating component b can be cooled. Then, the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the air volume suppressing filter  27   a  on the side of the air exhaust port (B)  22   a  is not closed (No in S 309 ), the air exhaust controlling circuit  17 A determines whether the air volume suppressing filter  27  on the side of the air exhaust port (A)  22  is closed as shown in  FIG. 17  or not (S 313 ). In this case, an air flow of an air volume of 60% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 40% flows to the air exhaust port (B)  22   a.    
     If the air volume suppressing filter  27  on the side of the air exhaust port (A)  22  is not closed (No in S 313 ), the air exhaust controlling circuit  17 A closes the air volume suppressing filter  27  (S 315 ). As a result, as shown in  FIG. 17 , an air flow of an air volume of 30% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 70% flows to the air exhaust port (B)  22   a.  In this way, when the air volume suppressing filter  27  on the side of the air exhaust port (A)  22  is closed to restrict the air volume blown to the air exhaust port (A)  22 , an air flow of a larger air volume can be supplied to the heat sink  21   a  on the side of the heat generating component b (the GPU  15 ), and the heat generating component b can be cooled. Then, the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the air volume suppressing filter  27  on the side of the air exhaust port (A)  22  is closed (Yes in S 313 ), the air exhaust controlling circuit  17 A determines whether the blocking shutter  26  on the side of the air exhaust port (A)  22  is closed as shown in  FIG. 18  or not (S 317 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  does not flow to the air exhaust port (A)  22  by the blocking shutter  26  on the side of the air exhaust port (A)  22 . Therefore, an air flow of an air volume of 100% flows to the air exhaust port (B)  22   a.    
     If the blocking shutter  26  on the side of the air exhaust port (A)  22  is not closed (No in S 317 ), the air exhaust controlling circuit  17 A closes the blocking shutter  26  (S 319 ). As a result, as shown in  FIG. 18 , an air flow of an air volume of 0% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 100% flows to the air exhaust port (B)  22   a.  In this way, when the blocking shutter  26  on the side of the air exhaust port (A)  22  is closed and the air flow to the air exhaust port (A)  22  is blocked, an air flow of a larger air volume can be supplied to the heat sink  21   a  on the side of the heat generating component b (the CPU  15 ), and the heat generating component b can be cooled. Then, the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the blocking shutter  26  on the side of the air exhaust port (A)  22  is closed (Yes in S 317 ), the heat generating component b cannot be cooled simply by controlling the blocking shutters  26 ,  26   a  and the air volume suppressing filters  27 ,  27   a,  and hence the air exhaust controlling circuit  17 A increases the number of rotations of the bidirectional air exhaust fan  23  (S 321 ). When the number of rotations of the bidirectional air exhaust fan  23  is increased, an air flow of a larger air volume can be supplied to the heat sink  21   a  for the heat generating component b (the GPU  15 ), and the heat generating component b can be cooled. Then, the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     In the case where it is necessary to cool the heat generating component b, if the heat generating component b can be cooled by controlling the set states of the blocking shutters  26 ,  26   a  and the air volume suppressing filters  27 ,  27   a,  the electronic apparatus  1 A controls the set states of the blocking shutters  26 ,  26   a  and the air volume suppressing filters  27 ,  27   a  to cool the heat generating component b. If not, the heat generating component b is cooled by increasing the number of rotations of the bidirectional air exhaust fan  23 . 
     Next, the case where the temperature of the heat generating component a (the CPU  11 ) is higher than that of the heat generating component b (the GPU  15 ) will be described with reference to the flowchart shown in  FIG. 19 . If the temperature of the heat generating component a is higher than that of the heat generating component b (No in S 301 ), the air exhaust controlling circuit  17 A determines whether it is necessary to increase the air volume for cooling the heat generating component a or not (S 401 ). In the case where the temperature of the heat generating component b is equal to or higher than a threshold value, for example, it is determined that an increase of the air volume is necessary. 
     If it is not necessary to increase the air volume for cooling the heat generating component a (No in S 401 ), it is not necessary to cool the heat generating component b in which the temperature is lower than the heat generating component a, and hence the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If it is necessary to increase the air volume for cooling the heat generating component a (Yes in S 401 ), the air exhaust controlling circuit  17 A determines whether the blocking shutter  26  on the side of the air exhaust port (A)  22  is closed as shown in  FIG. 18  or not, in order to seek means for cooling the heat generating component a without increasing the number of rotations of the bidirectional air exhaust fan  23  (S 403 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  does not flow to the air exhaust port (A)  22  by the blocking shutter  26  on the side of the air exhaust port (A)  22 , and hence an air flow of an air volume of 100% flows to the air exhaust port (B)  22   a.    
     If the blocking shutter  26  on the side of the air exhaust port (A)  22  is closed (Yes in S 403 ), the air exhaust controlling circuit  17 A opens the blocking shutter  26  (S 405 ). As a result, as shown in  FIG. 17 , an air flow of 30% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 70% flows to the air exhaust port (B)  22   a.  In this way, when the blocking shutter  26  on the side of the air exhaust port (A)  22  is opened, an air flow of a larger air volume can be supplied to the heat sink  21  on the side of the heat generating component a (the CPU  11 ), and the heat generating component a can be cooled. Then, the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the blocking shutter  26  on the side of the air exhaust port (A)  22  is not closed (No in S 403 ), the air exhaust controlling circuit  17 A determines whether the air volume suppressing filter  27  on the side of the air exhaust port (A)  22  is closed as shown in  FIG. 17  or not (S 407 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  hardly flows to the air exhaust port (A)  22  by the air volume suppressing filter  27  on the side of the air exhaust port (A)  22 . Therefore, an air flow of an air volume of 30% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 70% flows to the air exhaust port (B)  22   a.    
     If the air volume suppressing filter  27  on the side of the air exhaust port (A)  22  is closed (Yes in S 407 ), the air exhaust controlling circuit  17 A opens the air volume suppressing filter  27  (S 409 ). As a result, as shown in  FIG. 16 , an air flow of an air volume of 60% flows to the air exhaust port (A), and an air flow of 40% flows to the air exhaust port (B). In this way, when the air volume suppressing filter  27  on the side of the air exhaust port (A)  22  is completely opened, an air flow of a larger air volume can be supplied to the heat sink  21  on the side of the heat generating component a (the CPU  11 ), and the heat generating component a can be cooled. Then, the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the air volume suppressing filter  27  on the side of the air exhaust port (A)  22  is not closed (No in S 407 ), the air exhaust controlling circuit  17 A determines whether the air volume suppressing filter  27   a  on the side of the air exhaust port (B)  22   a  is closed as shown in  FIG. 15  or not (S 411 ). In this case, an air flow of an air volume of 80% flows to the air exhaust port (A), and an air flow of an air volume of 20% flows to the air exhaust port (B). 
     If the air volume suppressing filter  27   a  on the side of the air exhaust port (B)  22   a  is not closed (No in S 411 ), the air exhaust controlling circuit  17 A closes the air volume suppressing filter  27   a  (S 413 ). As a result, as shown in  FIG. 15 , an air flow of an air volume of 80% flows to the air exhaust port (A), and an air flow of an air volume of 20% flows to the air exhaust port (B). In this way, when the air volume suppressing filter  27   a  on the side of the air exhaust port (B)  22   a  is closed to restrict the air volume blown to the air exhaust port (B)  22   a,  an air flow of a larger air volume can be supplied to the heat sink  21  on the side of the heat generating component a (the CPU  11 ), and the heat generating component a can be cooled. Then, the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the air volume suppressing filter  27   a  on the side of the air exhaust port (B)  22   a  is closed (Yes in S 411 ), the air exhaust controlling circuit  17 A determines whether the blocking shutter  26   a  on the side of the air exhaust port (B)  22   a  is closed as shown in  FIG. 14  or not (S 415 ). In this case, the air flow generated by the bidirectional air exhaust fan  23  does not flow to the air exhaust port (B)  22   a  by the blocking shutter  26   a  on the side of the air exhaust port (B)  22   a.  Therefore, an air flow of an air volume of 100% flows to the air exhaust port (A), and an air flow of an air volume of 0% flows to the air exhaust port (B). 
     If the blocking shutter  26   a  on the side of the air exhaust port (B)  22   a  is not closed (No in S 415 ), the air exhaust controlling circuit  17 A closes the blocking shutter  26   a  (S 417 ). As a result, as shown in  FIG. 14 , an air flow of an air volume of 100% flows to the air exhaust port (A)  22 , and an air flow of an air volume of 0% flows to the air exhaust port (B)  22   a.  In this way, when the blocking shutter  26   a  on the side of the air exhaust port (B)  22   a  is completely closed and the air flow to the air exhaust port (B)  22   a  is blocked, an air flow of a larger air volume can be supplied to the heat sink  21  on the side of the heat generating component a (the CPU  11 ), and the heat generating component a can be cooled. Then, the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     If the blocking shutter  26   a  on the side of the air exhaust port (B)  22   a  is closed (Yes in S 415 ), the heat generating component a cannot be cooled simply by controlling the blocking shutters  26 ,  26   a  and the air volume suppressing filters  27 ,  27   a,  and hence the air exhaust controlling circuit  17 A increases the number of rotations of the bidirectional air exhaust fan  23  (S 419 ). When the number of rotations of the bidirectional air exhaust fan  23  is increased, an air flow of a larger air volume can be supplied to the heat sink  21  on the side of the heat generating component a (the CPU  11 ), and the heat generating component a can be cooled. Then, the process returns to step S 301  in which the air exhaust controlling circuit  17 A again determines whether the temperature of the heat generating component b is higher than that of the heat generating component a or not. 
     In the case where it is necessary to cool the heat generating component a, if the heat generating component a can be cooled by controlling the set states of the blocking shutters  26 ,  26   a  and the air volume suppressing filters  27 ,  27   a,  the electronic apparatus  1 A controls the set states of the blocking shutters  26 ,  26   a  and the air volume suppressing filters  27 ,  27   a,  to cool the heat generating component a. If not, the heat generating component a is cooled by increasing the number of rotations of the bidirectional air exhaust fan  23 . 
     According to the second embodiment, the exhaust air volumes of the air exhaust ports  22 ,  22   a  of the bidirectional air exhaust fan  23  are dynamically controlled based on the temperatures of the heat generating components a, b to suppress unnecessary air exhaust and enhance the cooling efficiency, whereby the number of rotations of the air exhaust fan  23  can be maintained to an optimum state and the heat generating components a, b can be cooled. 
     Although the electronic apparatuses  1 ,  1 A of the invention have been described in the case where the function of implementing the invention is previously stored in the apparatuses, the invention is not restricted to this. A similar function may be downloaded from a network to the apparatus, or a recording medium on which the similar function is stored may be installed on the apparatus. As the recording medium, a medium of any form such as a CD-ROM may be used as far as it can store programs and can be read by the apparatus.