Abstract:
To provide a dehumidification apparatus which can perpetually maintain the internal humidity of a disk drive low and can be installed on a cover or the like of the disk drive with a small space. Also, the dehumidification apparatus is controlled based on the internal humidity or the temperature condition inside and outside the disk drive, by which stable dehumidification can be effected without condensation etc. occurring inside and outside of the disk drive. There are provided a glass fiber which is arranged penetrating a cover of a hard disk drive (HDD) and extends inside and outside the HDD, and a heating member provided outside the HDD, so that the glass fiber on the outside is bonded to the heating member and is heated. Also, a cooling member is provided inside the HDD, and the glass fiber on the inside is bonded to the cooling member. Also, there is provided an apparatus for circulating air that is in contact with a heating portion and a cooling portion.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a dehumidification apparatus for reducing the humidity in a closed housing for a hard disk etc. and, more particularly, to a microminiature dehumidification apparatus suited for installation on a cover of a hard disk drive (hereinafter referred to as an HDD), and a dehumidification control system. 
     2. Description of the Related Art 
     As a method for keeping the humidity in a hard disk drive low, a conventional method has been used in which a desiccant is arranged in the hard disk drive. Thus, an improved and modern dehumidification system, including means to control the dehumidifying process, would be desirable. 
     SUMMARY OF THE INVENTION 
     Since a desiccant loses its hygroscopic property after it has absorbed a predetermined amount of water, it cannot keep the humidity in the HDD low for a long period of time. Further, water absorbed once by the desiccant is released again in the HDD for a long time, so that corrosion of the device in the HDD cannot be prevented from occurring from a long-term viewpoint. 
     An object of the present invention is to provide a microminiature, simply-constructed dehumidifier for removing water in a highly airtight device such as an HDD, a humidifier system in which an air circulation mechanism is added to the humidifier, and a dehumidification control system for keeping the interior of the device at a predetermined humidity or lower by controlling the dehumidifier and the dehumidification apparatus. 
     The dehumidifier in accordance with the present invention comprises a capillary member which is disposed penetrating a wall for forming two separated spaces so that a first portion thereof is located in one space and a second portion thereof is located in the other space, and the first portion and second portion are connected to each other, by which water can be moved between the two spaces by capillary action or phenomenon; and a heating portion for heating the first portion. 
     In this case, there may be provided a cooling portion for cooling the second portion of the capillary member. 
     Further, the construction may be such that the heating portion and cooling portion are heated and cooled, respectively, by the Peltier effect. 
     The dehumidification apparatus in accordance with the present invention comprises a first air circulator comprising a circulation pipe forming a circulation passage for air; and a pair of air feeders each of which is arranged at both ends of the circulation pipe so that air is fed in the same direction of the circulation passage and an air hole is closed at the time of non-operation; and 
     a dehumidifier comprising a heating portion formed in the circulation pipe; and a capillary member which is disposed penetrating a wall of the circulation pipe so that a first portion thereof is located inside the circulation pipe and a second portion thereof is located outside the circulation pipe while being connected to the first portion, by which water can be moved between the inside and the outside of the circulation pipe by the capillary phenomenon; the first portion of the capillary member located on the inside being heated by the heating portion. 
     In this case, a cooling portion may be formed outside the circulation pipe so that the second portion of the capillary member is cooled by the cooling portion. 
     The dehumidification apparatus of another construction comprises first and second air circulators each comprising a circulation pipe forming a circulation passage for air; and a pair of air feeders each of which is arranged at both ends of the circulation pipe so that air is fed in the same direction of the circulation passage and an air hole is closed at the time of non-operation; and 
     a dehumidifier comprising a heating portion formed in the first circulation pipe; and a capillary member in which a first portion and a second portion thereof are located so as to be connected to the inside of the first and second circulation pipes, respectively, by which water can be moved between the inside portions of both of the circulation pipes by capillary action or phenomenon; the first portion of the capillary member located inside the first circulation pipe being heated by the heating portion. 
     In this case, a cooling portion may be formed inside the second circulation pipe so that the second portion of the capillary member is cooled by the cooling portion. 
     The disk drive in accordance with the present invention comprises a housing formed with a pair of air holes; and the aforementioned dehumidification apparatus, and is constructed so that, of the pair of air feeders of the first air circulator, an air inflow port of the air feeder through which air flows into the circulation passage and an air outflow port of the air feeder through which air flows out of the circulation passage are spatially connected directly to each of the pair of air holes. 
     The disk drive of another construction comprises a housing formed with a pair of air holes; and the dehumidification apparatus having a pair of air feeders, and is constructed so that an air outflow port of the air feeder through which air flows out of the circulation passage, of the pair of air feeders of the first air circulator, and an air inflow port of the air feeder through which air flows into the circulation passage, of the pair of air feeders of the second air circulator, are spatially connected directly to each of the pair of air holes. 
     The dehumidification control system in accordance with the present invention has, in addition to the aforementioned disk drive, a humidity sensor disposed in the housing and a controller for controlling the dehumidification apparatus so that the dehumidification apparatus is operated when the humidity in the housing has a value not lower than a predetermined value. 
     The dehumidification control system of another construction has, in addition to the aforementioned disk drive, a pair of temperature sensors disposed inside and outside the housing and a controller for controlling the dehumidification apparatus so that the dehumidification apparatus is operated based on the temperatures inside and outside the housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing an embodiment of an HDD constructed in accordance with the present invention; 
     FIG. 2 is a top view showing a construction of an embodiment of a dehumidifier in accordance with the present invention; 
     FIG. 3 is a sectional view taken along the line A—A of the top view of FIG. 2; 
     FIG. 4 is a sectional view showing a construction of an embodiment of a dehumidification apparatus in accordance with the present invention; 
     FIG. 5 is a sectional view showing a construction of a micropump; 
     FIGS.  6 ( a )-( c ) are sectional views showing various states of operation of the micropump of FIG. 5; 
     FIG. 7 is a block diagram showing an embodiment of a dehumidification control system in accordance with the present invention; 
     FIG. 8 is a flowchart for illustrating the operation of a control unit of the dehumidification control system; 
     FIG. 9 is a flowchart illustrating the operation of a control unit of the dehumidification control system; 
     FIG. 10 is a top view showing a construction of another embodiment of a dehumidifier in accordance with the present invention; 
     FIG. 11 is a sectional view taken along the line B—B of the top view of FIG. 10; 
     FIG. 12 is a sectional view showing a construction of another embodiment of a dehumidification apparatus in accordance with the present invention; and 
     FIG. 13 is a sectional view showing a construction of still another embodiment of a dehumidification apparatus in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a perspective view showing an embodiment of an HDD in accordance with the present invention. An HDD  1  comprises a disk  4 , a base  2  for arranging an actuator arm  5  etc. at predetermined positions therein, and a cover  3  which is formed by an aluminum or stainless steel plate etc. and is installed above the base  2 , by which a substantially closed housing is formed. In this cover  3  is formed a dehumidifier  6 . 
     To make the construction clear, FIG. 1 shows a state in which the cover  3  is removed and moved in the direction away from the base  2 . 
     FIG. 2 is a top plan view showing a construction of an embodiment of a dehumidifier  6  in accordance with the present invention. FIG. 3 is a sectional view taken along the line A—A of FIG.  2 . 
     The dehumidifier  6  is inserted and positioned in an opening  3   a  formed in the cover  3  of the HDD  1 . One end of each of a prismatic n-type semiconductor  7  and p-type semiconductor  8 , which are components of the dehumidifier  6 , joins to the lower surface of a metallic conductive plate  9 . The other end of the n-type semiconductor  7  joins to the upper surface of a minus metal plate terminal  10 , and the other end of the p-type semiconductor  8  joins to the upper surface of a plus metal plate terminal  11 . 
     The upper surface of the metallic conductive plate  9  joins to the lower surface of a heating plate  12  formed of a ceramic, and the lower surface of the minus metal plate terminal  10  and the plus metal plate terminal  11  each joins to the upper surface of a cooling plate  13  formed of a ceramic. Side plates  14  form four sides so as to form a rectangular parallelepiped whose upper and lower faces are the heating plate  12  and the cooling plate  13 , respectively, which are opposed to each other at a predetermined interval in the vertical direction. 
     On one side face  14   a  of the side plate  14  is disposed a glass fiber holding member  16 . The glass fiber holding member  16  is formed with an elongated hole  16   a  along one side face of the side plate  14 . A glass fiber  15 , the amount of which is of such a degree as to close the elongated hole  16   a,  is arranged in such a state as to connect to the upper and lower sides of the glass fiber holding member  16  via the elongated hole  16   a.  The glass fiber  15  on the upside of the glass fiber holding member  16  is bent so as to extend along the heating plate  12 , and is bonded to the upper surface of the heating plate  12 . The glass fiber  15  on the downside of the glass fiber holding member  16  is bent so as to extend along the cooling plate  13 , and is bonded to the lower surface of the cooling plate  13 . 
     The dehumidifier  6  constructed as described above is inserted and positioned in the opening  3   a  formed in the cover  3  of the HDD  1  (FIG.  1 ), and further is fixed with an adhesive  17  packed to keep airtightness. To prevent a gap from being produced between the glass fiber  15  and the elongated hole  16   a,  an adhesive should preferably be packed therebetween for fixation to such a degree that the adhesive does not permeate in the glass fiber  15  to hinder the capillary phenomenon, described later. Also, the housing consisting of the cover  3  and the base  2  (FIG. 1) and the member for closing the opening  3   a  correspond to a wall for separating two spaces. 
     In the above described configuration, when a predetermined voltage is applied to between the minus metal plate terminal  10  and the plus metal plate terminal  11  via lead wires  18  and  19 , an electric current flows in a circuit formed by the plus metal plate terminal  11 , the p-type semiconductor  8 , the metallic conductive plate  9 , the n-type semiconductor  7 , and the minus metal plate terminal  10  in the direction indicated by arrows a, b and c shown in FIG.  3 . 
     At this time, as is known as the Peltier effect, the absorption and generation of heat take place at a junction of the plus metal plate terminal  11  and the p-type semiconductor  8 , a junction of the p-type semiconductor  8  and the metallic conductive plate  9 , a junction of metallic conductive plate  9  and the n-type semiconductor  7 , and a junction of the n-type semiconductor  7  and the minus metal plate terminal  10 . As a result, the plus metal plate terminal  11  and the minus metal plate terminal  10  are cooled, and the metallic conductive plate  9  is heated. 
     Therefore, inside the HDD  1  (FIG.  1 ), the cooling plate  13  that is in contact with the plus metal plate terminal  11  and the minus metal plate terminal  10  is cooled, so that water in the HDD  1  condenses on the cooling plate  13  and at an adsorbing portion  15   b  of the glass fiber  15  which is cooled by the contact with the cooling plate  13 . The water condensing at the adsorbing portion  15   b  moves successively in the glass fiber  15  toward the evaporating portion  15   a  by the capillary phenomenon. 
     On the other hand, outside the HDD  1  (FIG.  1 ), the heating plate  12  that is in contact with the metallic conductive plate  9  is heated, so that the water reaching the evaporating portion  15   a  of the glass fiber  15  that is in contact with the heating plate  12  is evaporated successively by this heat. Thus, the water in the HDD  1  is removed to the outside thereof. 
     As described above, according to the dehumidifier  6  in accordance with an embodiment of the present invention, the water in the HDD  1  can be discharged efficiently to the outside only by using a simple construction and a small space. 
     FIG. 4 is a sectional view showing a construction of an embodiment of a dehumidification apparatus in accordance with the present invention. 
     This dehumidification apparatus  21  is, like, for example, the aforementioned dehumidifier  6  (FIG.  3 ), installed on the cover  3  of the HDD  1  shown in FIG.  1 . In this case, the cover  3  is formed with a suction hole  3   b  and an exhaust hole  3   c.  These holes are closely connected to an inlet hole  22   a  of a micropump  22 , described later, and an outlet hole  23   b  of a micropump  23 , respectively, in an airtight condition inside the cover. 
     One end  26   a  of an outside air circulation pipe  26  is closely connected to the peripheral portion of the outlet hole  22   b  of the micropump  22 , and the other end  26   b  thereof is closely connected to the peripheral portion of the inlet hole  23   a  of the micropump  23 . Therefore, a circulation passage  26   c  of the outside air circulation pipe  26  communicates with the outside of the HDD  1  via the micropump  22  or the micropump  23 . 
     One end  27   a  of an inside air circulation pipe  27  is closely connected to the peripheral portion of an outlet hole  24   b  of a micropump  24 , and the other end  27   b  thereof is closely connected to the peripheral portion of an inlet hole  25   a  of a micropump  25 . An inlet hole  24   a  of the micropump  24  and an outlet hole  25   b  of the micropump  25  are located in the HDD  1 . Therefore, a circulation passage  27   c  of the inside air circulation pipe  27  communicates with the inside of the HDD  1  via the micropump  24  or the-micropump  25 . 
     The circulation passage  26   c  of the outside air circulation pipe  26  and the circulation passage  27   c  of the inside air circulation pipe  27  are spatially connected via a connection hole  28  formed at the central portion of these passages. In this connection hole  28 , the aforementioned dehumidifier  6  shown in FIG. 2 is inserted and fixed with no gap in such a manner that the heating plate  12  (FIG. 3) faces the circulation passage  26   c.    
     Since the micropumps  22 ,  23 ,  24  and  25  have the same construction though the operation timing thereof is different, only the internal construction of the micropump  22  is shown in FIG. 5 as an example, and the operation thereof will be described with reference to an operation view of FIG.  6 . 
     As shown in FIG. 5, the micropump  22  comprises a base  31  and three microvalves  32 ,  33  and  34  disposed at predetermined positions of the base  31 . The base  31  is formed with the inlet hole  22   a  of the micropump  22 , which corresponds to an air inlet, the outlet hole  22   b  of the micropump  22 , which corresponds to an air outlet, and passage holes  31   a  and  31   b  which constitute intermediate passages of air. 
     The microvalves  32 ,  33  and  34  have the same construction though the operation timing thereof is different, and therefore only the construction of the microvalve  32  is explained. Other microvalves  33  and  34  will be explained in the later description of operation as necessary. 
     The microvalve  32  comprises a soft magnet film  32   a,  which is placed on the base  31  so as to close the inlet hole  22   a  and one of openings of the passage hole  31   a  of the base  31 , a passage cover  32   b,  which forms a space  32   g  for allowing the soft magnet film  32   a  to be deformed so that the inlet hole  22   a  is spatially connected to the passage hole  31   a  as described later, and a core  32   c,  which forms an electromagnet  32   e  by winding a coil  32   d  and is disposed so as to be close to the soft magnet film  32   a  with both end portions thereof projecting into the space  32   g.    
     Similarly, the microvalve  34  is constructed so that the soft magnet film  34   a  thereof is disposed so as to close the outlet hole  22   b  and one opening of the passage hole  31   b  of the base  31 , and the microvalve  33  is constructed so that the soft magnet film  33   a  thereof is disposed so as to close the other opening of the passage hole  31   a  and the passage hole  31   b  of the base  31 . 
     In the above described construction, when the electromagnet  32   e  of the microvalve  32  is first turned on, the soft magnet film  32   a  is attracted by the electromagnet  32   e  and is curved as shown in FIG.  6 ( a ), so that the inlet hole  22   a  and the passage hole  31   a  are connected spatially to each other, and therefore air entering through the inlet hole  22   a  flows into a variable space  32   f  formed in the microvalve  32 . Next, after the electromagnet  33   e  of the microvalve  33  is turned on, the electromagnet  32   e  of the microvalve  32  is turned off, by which the inflow air is caused to flow into a variable space  33   f  of the microvalve  33 . 
     Next, after the electromagnet  34   e  of the microvalve  34  is turned on, the electromagnet  33   e  of the microvalve  33  is turned off, by which the inflow air is further caused to flow into a variable space  34   f  of the microvalve  34  as shown in FIG.  6 ( b ). Finally, the electromagnet  34   e  of the microvalve  34  is turned off, by which the air having flowed in through the inlet hole  22   a  is discharged through the outlet hole  22   b  as shown in FIG.  6 ( c ). 
     By continuously repeating a series of the above described operations, the micropump  22  can always discharge, through the outlet hole  22   b,  the air having flowed in through the inlet hole  22   a.  The state in which the micropump sends air by an interlocked operation of three microvalves in this manner is hereinafter referred to simply as an operating condition of micropump. 
     The dehumidification apparatus  21  (FIG. 4) forms a flow of air by operating the four micropumps  22 ,  23 ,  24  and  25  with the above described construction, and thereby dehumidifies the interior of the HDD  1  as described below. 
     When all of the micropumps  22 ,  23 ,  24  and  25  are turned into an operating condition, the outside air of the HDD  1  (FIG. 1) flows in the circulation passage  26   c  of the outside air circulation pipe  26  in the arrow-marked direction, and on the other hand, the inside air of the HDD  1  (FIG. 1) flows in the circulation passage  27   c  of the inside air circulation pipe  27  in the arrow-marked direction. In this state, the aforementioned predetermined voltage is applied to the metal plate terminals  10  and  11  (FIG. 3) of the dehumidifier  6 , by which the water in the HDD  1  is discharged from the evaporating portion  15   a  of the glass fiber  15  into the circulation passage  26   c.    
     As described above, according to the dehumidification apparatus  21  in accordance with an embodiment of the present invention, since new inside air and outside air are always supplied to the vicinity of the dehumidifier  6 , dry inside air and wet outside air do not stay around the dehumidifier  6 , thereby increasing the dehumidification efficiency. Also, since the inside air pressure is not decreased by the dehumidification, there is no fear of an adverse effect of a flying head etc. on the operation of HDD. Further, since the inlet and outlet holes of each of the micropumps are closed in the stopped state, the airtightness of HDD is maintained when the dehumidification apparatus  21  is not in operation. 
     Although the direction in which the inside air flows in the inside air circulation pipe  27  is the same as the direction in which the outside air flows in the outside air circulation pipe  26  in the construction shown in FIG. 4, these directions may be opposite to each other. Also, the outside and inside air circulation pipes  26  and  27  may be crossed obliquely or at right angles, not being in parallel. 
     FIG. 7 is a block diagram showing a basic configuration of an embodiment of a dehumidification control system in accordance with the present invention. FIGS. 8 and 9 are flowcharts for illustrating the operation of a control unit for the dehumidification control system shown in FIG.  7 . 
     In FIG. 7, a humidity sensor  42 , which is disposed at a predetermined position (not shown) inside the HDD  1  (FIG.  1 ), sends out the humidity information in the HDD  1  to a control circuit  41 . A temperature sensor  43 , which is disposed at a predetermined position (not shown) outside the HDD  1 , sends out the external temperature information outside the HDD  1  to a control circuit  41 , and a temperature sensor  44 , which is disposed at a predetermined position (not shown) inside the HDD  1 , sends out the internal temperature information inside the HDD  1  to a control circuit  41 . For simplifying the explanation, FIG. 7 shows the humidity sensor  42  and both of the temperature sensors  43  and  44 . However, either one of the humidity sensor  42  and a pair of temperature sensors  43  and  44  may be disposed selectively according to the later-described operation mode. 
     FIG. 8 is a flowchart for a dehumidification control system that is provided with the humidity sensor  42  (FIG.7) inside the HDD  1 . When the HDD  1  is turned on, the control circuit  41  checks whether or not the internal humidity in the HDD  1  exceeds a predetermined value P (Step  1 ). If the humidity exceeds the predetermined value P, the four micropumps  22 ,  23 ,  24  and  25  of the dehumidification apparatus  21  shown in FIG. 4 is made in the operating condition to circulate the outside air and the inside air through the circulation passages  26   c  and  27   c,  respectively, and also a predetermined voltage is applied to the pair of metal plate terminals  10  and  11  (FIG. 3) of the dehumidifier  6  to operate the dehumidification apparatus  21  (Step  2 ). On the other hand, if the internal humidity has a value equal to or lower than the predetermined value P, the dehumidification apparatus  21  is not operated (Step  3 ). 
     The control circuit  41  checks the humidity in the HDD  1  as described above each time that time T shown in Step  4  elapses, and operates or stops the dehumidification apparatus  21  according to the result. 
     FIG. 9 is a flowchart for a dehumidification control system that is, provided with the temperature sensors  43  and  44  inside and outside the HDD  1 . When the HDD  1  is turned on, the control system  41  checks whether the external temperature is not higher than 0° C. (Step  1 ). If the external temperature is not higher than 0° C., the dehumidification apparatus  21  is kept stopped (Step  4 ). This operation is performed to prevent the water discharged into the circulation passage  26   c  of the outside air circulation pipe  26  from freezing in the passage. 
     Next, a difference between the external temperature and the internal temperature is checked, and if the external temperature is lower than the internal temperature by a predetermined value J 1  or more, the dehumidification apparatus  21  is kept stopped (Steps  2  and  4 ). This operation is performed to prevent the water discharged to the outside from condensing near the exhaust hole  3   c  (FIG. 4) in the cover  3 . 
     Next, a difference between the external temperature and the internal temperature is checked, and if the external temperature is higher than the internal temperature by a predetermined value J 2  or more, the dehumidification apparatus  21  is operated at the highest efficiency set for emergency (Steps  3  and  6 ). This operation is performed to prevent the water in the HDD  1  from condensing inside. If the result of judgment in Step  2  is Yes and the result of judgment in Step  3  is No, the dehumidification apparatus  21  is operated at an efficiency set for normal operation (Steps  2 ,  3  and  5 ). The operation efficiency of the dehumidification apparatus  21  is determined by the speed value of operation timing of each micropump explained with reference to FIG.  6  and the voltage value applied to the dehumidifier  6 , and is set appropriately. 
     Further, the control circuit  41  checks the temperatures inside and outside the HDD  1  as described above each time that time T shown in Step  7  elapses, and operates or stops the dehumidification apparatus  21  according to the result. 
     As described above, according to the dehumidification control system in accordance with an embodiment of the present invention, the humidity inside the HDD or the temperatures inside and outside the HDD are detected, and the operation of the dehumidification apparatus is controlled based on the result. Therefore, the interior of the HDD can be dehumidified in the best condition. Also, although the humidity control by the detection of humidity and the humidity control by the detection of temperature have been explained as a separate system in the above embodiment, a system in which both controls are combined may be configured. For example, the system configuration may be such that the humidity inside the HDD is checked, and if the humidity has a value not lower than the predetermined value P, the program proceeds to Step  1  in FIG.  9 . 
     FIG. 10 is a top view showing a construction of another embodiment of a dehumidifier in accordance with the present invention, and FIG. 11 is a sectional view taken along the line B—B of FIG.  10 . 
     This dehumidifier  51  is, like the aforementioned dehumidifier  6  shown in FIG. 3, inserted and positioned in the opening  3   a  formed in the cover  3  of the HDD  1  (FIG.  1 ). A partitioning plate  52 , which is a component of the dehumidifier  51 , is fitted in the opening  3   a  and fixed with no gap by using an adhesive  56  packed to keep airtightness. The partitioning plate  52  is formed with an elongated hole  52   a  along one side thereof, and a flat plate shaped heating member  53  is fixed to the top surface of the partitioning plate  52 . 
     A glass fiber  55 , the amount of which is of a degree such as to close the elongated hole  52   a,  is arranged in such a state as to connect to the upper and lower sides of the partitioning plate  52  via the elongated hole  52   a.    
     The glass fiber  55  on the upside of the partitioning plate  52  is bent so as to extend along the heating member  53 , and is bonded to the upper surface of the heating member  53 . The glass fiber  55  on the downside of the partitioning plate  52  is free without being fixed. 
     To prevent a gap from being produced between the glass fiber  55  and the elongated hole  52   a,  an adhesive should preferably be packed therebetween for fixation to such a degree that the adhesive does not permeate in the glass fiber  55  to hinder the capillary phenomenon. Also, the housing consisting of the cover  3  and the base  2  (FIG. 1) and the partitioning plate  52  correspond to a wall for separating two spaces. 
     In the above described construction, when a voltage is applied to an electrode, not shown, of the heating member  53  to heat the heating member  53 , the water contained in an evaporating portion  55   a  of the glass fiber  55  in contact with the heating member evaporates, so that the internal water adhering to an adsorbing portion  55   b  of the glass fiber  55  in the HDD  1  moves successively in the glass fiber  55  toward the evaporating portion  55   a  by the capillary phenomenon. Thus, the water in the HDD  1  is removed to the outside. 
     As described above, according to the dehumidifier  51  in accordance with the embodiment of the present invention, the water in the HDD  1  can be discharged to the outside by a simple construction. Also, the dehumidifier  51  can be used in place of the dehumidifier  6  in the aforementioned dehumidification apparatus  21  shown in FIG. 4, and further the dehumidification apparatus provided with the dehumidifier  51  can be used for the dehumidification control system in accordance with the present invention shown in FIG.  7 . In this case, however, the control unit  41  controls the voltage applied to the electrode, not shown, of the heating member  53 . 
     FIG. 12 is a sectional view showing a construction of another embodiment of a dehumidification apparatus in accordance with the present invention. 
     A dehumidification apparatus  61  is, like, for example, the aforementioned dehumidifier  6 , installed on the cover  3  of the HDD  1  shown in FIG.  1 . In this case, the cover  3  is formed with the suction hole  3   b  and the exhaust hole  3   c.  These holes are closely connected to an inlet hole  62   a  of a micropump  62  and an outlet hole  63   b  of a micropump  63 , respectively, in an airtight condition inside the cover. Four micropumps  62 ,  63 ,  64  and  65  used in this embodiment are the same as the micropump  22  shown in FIG.  5 . FIG. 12 shows the directivity of the disposed micropump by showing the inlet and outlet holes thereof. 
     One end  66   a  of an inflow pipe  66  is closely connected to the peripheral portion of an outlet hole  62   b  of the micropump  62 , and the other end  66   b  thereof is closely connected to the peripheral portion of an inlet hole  64   a  of the micropump  64 . On the other hand, one end  67   a  of an outflow pipe  67  is closely connected to the peripheral portion of an inlet hole  63   a  of the micropump  63 , and the other end  67   b  thereof is closely connected to the peripheral portion of an outlet hole  65   b  of the micropump  65 . Also, both of an output hole  64   b  of the micropump  64  and an inlet hole  65   a  of the micropump  65  are located in the HDD  1 . 
     Therefore, a circulation passage  66   c  of the inflow pipe  66  communicates with the outside and inside of the HDD  1  via the micropumps  62  and  64 , and a circulation passage  67   c  of the outflow pipe  67  communicates with the outside and inside of the HDD  1  via the micropumps  63  and  65 . 
     The circulation passage  66   c  of the inflow pipe  66  and the circulation passage  67   c  of the outflow pipe  67  are connected spatially to each other by a connection hole  68  formed at the central portion of these passages. In this connection hole  68 , the aforementioned dehumidifier  6  shown in FIG. 2 or the dehumidifier  51  shown in FIG. 10 is inserted and fixed with no gap. At this time, the dehumidifier is disposed so that the evaporating portion thereof is located on the side of the outflow pipe. 
     In the above construction, when all of the micropumps  62 ,  63 ,  64  and  65  are made in an operating condition, the outside air of the HDD  1  (FIG. 1) flows through the circulation passage  66   c  of the inflow pipe  66  in the arrow-marked direction, entering the HDD  1 . On the other hand, the inside air of the HDD  1  (FIG. 1) flows through the circulation passage  67   c  of the outflow pipe  67  in the arrow-marked direction, flowing out to the outside of the HDD  1 . When the aforementioned predetermined voltage is applied to the metal plate terminals  10  and  11  (FIG. 3) of the dehumidifier  6  in this state, the dehumidifier  6  absorbs water from the outside air flowing into the HDD  1  through the circulation passage  66   c  and discharges the water into the inside air flowing out to the outside of the HDD  1  through the circulation passage  67   c.    
     Therefore, water with low humidity flows into the HDD  1 , so that as a result, the water in the HDD  1  can be removed to the outside. In order to prevent harmful chemical substances from entering when the outside air flows into the HDD  1 , a chemical filter  69  may be installed to the outlet hole  64   b  of the micropump  64  to prevent inflow of the chemical substances. 
     As described above, according to the dehumidification apparatus  61  in accordance with the present invention, the water in the HDD  1  can be removed efficiently. Also, it can be used in the dehumidification control system in accordance with the present invention shown in FIG.  7 . Also, the operation of the micropumps  62  and  64  and the operation of the micropumps  63  and  65  are controlled separately to control the inflow amount of air flowing into the HDD  1  and the outflow amount of air flowing out of the HDD  1 , by which the air pressure in the HDD  1  can also be controlled. Further, since the inlet and outlet holes of each of the micropumps are closed in the stopped condition, the airtightness of the HDD  1  is maintained when the dehumidification apparatus  61  is not operated. 
     FIG. 13 is a sectional view showing a construction of still another embodiment of a dehumidification apparatus in accordance with the present invention. As is apparent from the figure, this dehumidification apparatus  71  has exactly the same construction as that of the dehumidification apparatus  21  shown in FIG. 4 except that the inside air circulation pipe  27  and the micropumps  24  and  25  are eliminated from the dehumidification apparatus  21 , and therefore, the detailed description thereof is omitted. 
     According to the dehumidification apparatus  71 , although the dehumidification efficiency somewhat lowers as compared with the dehumidification apparatus  21 , the same effects as those of the aforementioned dehumidifier  21  can be achieved in other respects. 
     Although terms of “upper”, “lower”, and the like have been used in the explanation of the above described embodiments, these terms have been used for convenience. The absolute positional relationship in the condition in which the apparatus is used is not limited. 
     Although glass fiber has been used as a capillary member for producing the capillary phenomenon in the above described embodiments, the material is not limited to this, and cotton cloth or the like can be used. 
     Also, a micropump has been used as an air feed means in the above described embodiments, the air feed means is not limited to this, and a microminiature fan with shutter can be used. 
     Also, an example in which the dehumidification apparatus  21  provided in the HDD, shown in FIG. 4, is controlled shown as a dehumidification control system is shown in the above described embodiments, the dehumidification control system is not limited to this, and can be configured so as to control the dehumidifier  6  similarly provided in the HDD, shown in FIG. 2, or the dehumidifier  51  shown in FIG.  10 . 
     Also, although an example in which the present invention is applied to an HDD is shown in the above described embodiments, the present invention is not limited to this, and can be applied to an optical disk drive or other precision devices. 
     Further, although a dehumidifier or a dehumidification apparatus has been installed to a cover in the above described embodiments, various modes are possible; for example, the dehumidifier or the dehumidification apparatus may be installed to a base. 
     According to the dehumidifier in accordance with the present invention, the water in a closed space can be discharged to the outside with a simple construction. 
     According to the dehumidification apparatus in accordance with the present invention, the water in a closed space can be discharged to the outside effectively. Also, since the inside air pressure is not decreased by the dehumidification, when the present invention is applied to an HDD, there is no fear of an adverse effect of a flying head etc. on the internal operation. Further, since the inlet and outlet holes of each of the micropumps are closed in the stopped state of the dehumidification apparatus, the airtightness of HDD is maintained. 
     According to the other dehumidification apparatus in accordance with the present invention, by controlling the inflow amount of air flowing into a closed space and the outflow of air flowing out to the outside, the air pressure in the HDD  1  can also be controlled. 
     According to the dehumidification control system in accordance with the present invention, the humidity in the HDD or the temperatures inside and outside the HDD are detected, and the operation of dehumidification apparatus is controlled according to the detection result. Therefore, the interior of the HDD can be dehumidified in the best condition.