Abstract:
An electronic apparatus includes a component to which a pressure is applied or which provides vibration, a heat absorbing member, a heat dissipating member, an elastomer bag which receives a pressure or the vibration from the component, a first check valve connected to a port of the elastomer bag, a second check valve connected to another port of the elastomer bag, and a coolant which flows passing through the heat absorbing member, the first check valve, the elastomer bag, the second check valve, and said heat dissipating member.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to cooling of an electronic apparatus, and more particularly to an energy-saving cooling system for use in a small electronic device such as a notebook personal computer (PC).  
         BACKGROUND OF THE INVENTION  
         [0002]    With the recent increasing processing rates of notebook PCs, the amount of heat diffused from their heat producing components, such as CPUs, hard disk drives, and graphics chips has been increasing. Such heat producing components, however, cannot be sufficiently cooled by conventional components, such as a heat sink, a heat pipe, and a cooling fan.  
           [0003]    Conventionally, it is known that a notebook PC employs a closed loop system constructed of a tube that efficiently cools the CPU by circulating a liquid coolant in the tube from a heat absorbing element to a heat dissipating element and back to the heat absorbing element by means of an electric motor.  
           [0004]    In Japanese Patent Application Laid-Open Publication (JP-A) HEI 7-243738 published on Sep. 19, 1995, Takeda et al. disclose an electronic apparatus cooling device using a magnetic fluid vibration motor. In this cooling device, a tube forms a closed loop, and a spherical magnetic member is caused to vibrate along the tube by means of an external magnetic field formed by an exciting current flowing through a coil in a driving section of the tube, to cause the liquid coolant in the tube to flow back and forth between the heat absorbing element and the heat dissipating element, whereby efficient cooling is achieved. The spherical magnetic element has an outer diameter which is substantially equal to an inner diameter of the tube. In an alternative configuration, the cooling device includes a tube of a closed loop having a branch tube equipped with such a driving section, and a one-way valve is provided on each side or one side of the branching section of the closed loop tube, wherein the liquid coolant is circulated by causing the spherical magnetic element to vibrate along the branch tube.  
           [0005]    Forced cooling in common electronic apparatuses requires electric energy. In a battery operated electronic apparatus, however, it is desirable to reduce electric energy consumption significantly.  
           [0006]    The inventors have recognized the need for an efficient energy-saving cooling system for an electronic apparatus.  
           [0007]    An object of the present invention is to provide energy-saving cooling in an electronic apparatus.  
           [0008]    Another object of the invention is to provide cooling in an electronic apparatus by circulating a fluid coolant by means of an energy-saving driving power.  
         SUMMARY OF THE INVENTION  
         [0009]    In accordance with an aspect of the present invention, an electronic apparatus includes a component to which a pressure is applied or which provides vibration, a heat absorbing member, a heat dissipating member, an elastomer bag which receives a pressure or the vibration from the component, a first check valve connected to a port of the elastomer bag, a second check valve connected to another port of the elastomer bag, and a coolant which flows passing through the heat absorbing member, the first check valve, the elastomer bag, the second check valve, and said heat dissipating member.  
           [0010]    The elastomer bag is placed in close proximity to the component. The elastomer bag in combination with the first and second check valves operates in such a manner as to pump the coolant, in response to the application and releasing of the pressure from the component or to the vibration therefrom.  
           [0011]    The electronic apparatus further includes an accumulator tank for storing said coolant, and the tank may be connected to the heat dissipating member. The accumulator tank may contain therein a closed or sealed air bag.  
           [0012]    The electronic apparatus may further include a second elastomer bag, which is connected to third and fourth check valve, and which receives a pressure or vibration from a second component.  
           [0013]    According to the invention, in an electronic apparatus, energy-saving cooling can be provided and a fluid coolant can be circulated by means of an energy-saving driving power.  
           [0014]    Throughout the drawings, similar symbols and numerals indicate similar items and functions. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 shows an electronic apparatus, such as a notebook personal computer or a PDA, to which the present invention is applicable;  
         [0016]    [0016]FIG. 2 shows a partially cutaway top plan view illustrating a display housing and a main unit housing, in accordance with an embodiment of the present invention, when the display housing is opened so that the display surface of the display housing makes an angle of 180 degrees with the manual operation surface of the main unit housing in the electronic apparatus of FIG. 1;  
         [0017]    [0017]FIGS. 3A and 3B show a top plan view and a front side view of the elastomer bag or tube, respectively;  
         [0018]    [0018]FIG. 4A shows a perspective view of the accumulator tank of FIG. 2, and FIG. 4B shows a vertical cross sectional view of the accumulator tank taken along line  4 B- 4 B in FIG. 4A.;  
         [0019]    [0019]FIGS. 5A and 5B show the structure and operation of a known check valve;  
         [0020]    [0020]FIGS. 6A and 6B show the structure and operation of another known check valve;  
         [0021]    [0021]FIGS. 7A and 7B show the structure and operation of a further known check valve;  
         [0022]    [0022]FIG. 8 shows a partially cutaway top plan view illustrating the display housing and the main unit housing, in accordance with another embodiment of the invention, when the display housing is opened so that the display surface of the display housing makes an angle of 180 degrees with the manual operation surface of the main unit housing in the electronic apparatus of FIG. 1;  
         [0023]    [0023]FIG. 9 shows a partially cutaway top plan view illustrating the display housing and the main unit housing of FIG. 1, in accordance with a further embodiment of the invention;  
         [0024]    [0024]FIG. 10 shows a partially cutaway top plan view illustrating the display housing and the main unit housing in the electronic apparatus of FIG. 1, in accordance with a still further embodiment of the invention;  
         [0025]    [0025]FIG. 11 shows a partially cutaway top plan view illustrating the display housing and the main unit housing in the electronic apparatus of FIG. 1, in accordance with a still further embodiment of the invention;  
         [0026]    [0026]FIG. 12 shows a partially cutaway top plan view illustrating the display housing and the main unit housing in the electronic apparatus of FIG. 1, in accordance with a still further embodiment of the invention; and  
         [0027]    [0027]FIG. 13 shows a parallel combination of a pump element consisting of the series connection of the check valves and elastomer bag of FIG. 2, a pump element consisting of the series connection of the check valves and elastomer bag of FIG. 8, a pump element consisting of the series connection of the check valves and elastomer bag of FIG. 9, and a pump element consisting of the series connection of the check valves and elastomer bag of FIG. 10. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]    [0028]FIG. 1 shows an electronic apparatus  10 , such as a notebook personal computer (PC) or a PDA (Personal Digital Assistant), to which the present invention is applicable. The electronic apparatus  10  includes a display housing  20  and a main unit housing  30 . A display  22 , such as a liquid crystal display (LCD), is fixed in the display housing  20 . The main unit housing  30  accommodates a keyboard  32 , a pointing device  34 , a rechargeable battery  36 , a speaker  38 , a CD/DVD drive  40 , a jog dial  42 , a cooling fan, a processor, a hard disk drive and the like, which are fixed in the main unit housing  30 . A palm rest  44  for supporting user&#39;s hands placed on the left and right sides of the pointing device  34  is provided on the upper surface of the main unit housing  30 .  
         [0029]    [0029]FIG. 2 is a partially cutaway top plan view illustrating the display housing  20  and the main unit housing  30 , in accordance with an embodiment of the present invention, when the display housing  20  is opened so that the display surface of the display housing  20  makes an angle of 180 degrees with the manual operation surface of the main unit housing  30  in the electronic apparatus  10  of FIG. 1. The display housing  20  contains therein heat dissipating members  220  and  221 , which are placed behind the display  22 , and through which a liquid coolant circulates to dissipate heat from the rear panel of the display housing  20 , and also an accumulator tank  210 , which is connected between the dissipating members  220  and  221  and used to store the liquid coolant. The tank  210  has a watertight construction to prevent the liquid coolant from leaking out through any portion other than its inlet and outlet ports. The liquid coolant may be an antifreeze liquid for example. The heat dissipating members  220  and  221  may be bent aluminum tubes for example. The tubes are arranged in such a manner as to contact the rear panel of the display housing  20 .  
         [0030]    In FIG. 2, the main unit housing  30  contains therein: a heat absorbing member  340  which is placed in close proximity to a heat generating portion  300 , which may be the CPU, hard disk drive, graphics chip and/or the like, in the electronic apparatus  10 ; check valves  442  and  462  which allow the liquid coolant to flow in only one direction and thus prevent it from flowing backward; and an elastomer bag or tube  412  which is connected between the check valves  442  and  462 . The heat absorbing member  340 , the check valves  442  and  462  and the elastomer bag  412  are located behind the manual operation surface on the side of the keyboard  32 . In the figure, the check valves  442  and  462  are represented by symbols conforming to the JIS (Japanese Industrial Standard). In FIG. 2, the elastomer bag  412  is located behind the pointing device  34  and the palm rest  44 . The pointing device  34  moves and vibrates vertically when clicked or pressed by a finger. The palm rest  44  slightly moves downward vertically when hands are placed thereon. The heat absorbing member  340  may be a bent aluminum tube for example. Preferably, the tube is arranged in such a manner as to contact the heat generating portion  300 .  
         [0031]    The bottom left outlet port of the heat dissipating member  220  is connected to the inlet port of the heat absorbing member  340  via a rubber tube  222  running between the two housings or cases  20  and  30  and via a tube  322 . The outlet port of the heat absorbing member  340  is connected to the inlet port of the check valve  442  via a tube  324 . The outlet port of the check valve  442  is connected to the inlet port of the elastomer bag  412  via a tube  342 . The outlet port of the elastomer bag  412  is connected to the inlet port of the check valve  462  via a tube  362 . The outlet port of the check valve  462  is connected to the bottom right inlet port of the heat dissipating member  221  via a tube  330  and a rubber tube  224 . The rubber tubes  222  and  224  are used and adapted to provide the fluid flow path regardless of the angle between the display housing  20  and the main unit housing  30 . The closed loop fluid circuit is thus formed. The tubes  322 ,  324 ,  342 ,  362 , and  330  each may be formed of a plastic or metal tube, the outer diameter of which is about 1 to 3 mm, and the cross section of which may be elliptical in shape for example.  
         [0032]    In operation, when the user operates the pointing device  34  with his or her hands placed on the palm rest  44 , the elastomer bag  412 , in response to the repetitive pressing and vibration associated with the operation, compresses and expands in a repetitive manner and thus pumps the liquid coolant contained therein. With the elastomer bag  412  repetitively compressing, the liquid coolant contained therein is pumped through the check valve  462  and gradually flows into the heat dissipating member  221  where the heat is dissipated. After that, the liquid coolant flows into the accumulator tank  210 . With the elastomer bag  412  repetitively expanding, the liquid coolant in the tank  210  flows out and is cooled through the heat dissipating member  220 , and flows into the heat absorbing member  340  where the liquid coolant absorbs heat from the heat generating portion  300 . After that, the liquid coolant is passed through the check valve  442  and gradually flows back into the elastomer bag  412 . In this way, the liquid coolant circulates between the heat absorbing member  340  and the heat dissipating members  220  and  221  and cools the heat generating portion  300  without consuming energy or power from the AC power supply or the DC battery  36  of the electronic apparatus  10 .  
         [0033]    [0033]FIG. 3A shows a top plan view of the elastomer bag or tube  412 - 420 , described above in connection with FIG. 2 and described later in connection with FIGS.  8  to  12 . FIG. 3B shows a front side view of the elastomer bag  412 - 420 . The elastomer bag  412  is made of a rubber or soft plastic material, and is substantially ellipsoidal in shape with its center portion bulging. The elastomer bag  412  is placed facing the pressure or vibration source so that the substantially flat surface of the center portion receives the pressure and vibration, the opposite surface thereof being supported on a support plate  421 . For simplicity of illustration, the support plate  421  is not shown in FIG. 2.  
         [0034]    [0034]FIG. 4A shows a perspective view of the accumulator tank  210  of FIG. 2. FIG. 4B shows a vertical cross sectional view of the accumulator tank  210  taken along the line  4 B- 4 B in FIG. 4A. The accumulator tank  210  contains a rubber or plastic air bag  212  which is expandable and compressible like a rubber balloon. The air bag  212  is located in the upper part of the accumulator tank  210 , and its movement is limited by a grid  214  so that it will not close the inlet and outlet ports for the liquid coolant  216 , regardless of where and how the electronic apparatus  10  is placed. Alternatively, such an air bag may be placed in the lower part of the tank  210 . When the elastomer bag  412  is compressed, causing the liquid coolant  216  to flow into the tank  210  and thus increasing the amount of fluid stored therein, the air bag  212  compresses. Conversely, when the elastomer bag  412  expands, causing the liquid coolant  216  to flow out of the tank  210  and thus reducing the amount of fluid stored therein, the air bag  212  expands. In other words, the elastomer bag  412  compresses and expands in conjunction with the elastic force of the air bag  212 .  
         [0035]    [0035]FIGS. 5A and 5B show the structure and operation of a known check valve that can be used as the check valves  442  and  462 . The check valve shown in FIGS. 5A and 5B has a substantially cone-shaped diaphragm protruding axially in the rightward direction. As shown in FIG. 5A, the check valve allows the liquid coolant to flow only in the rightward direction in which the diaphragm protrudes. However, as shown in FIG. 5B, the check valve prevents the liquid coolant from flowing backward in the direction opposite to the direction in which the diaphragm protrudes.  
         [0036]    [0036]FIGS. 6A and 6B show the structure and operation of another known check valve that can be used as the check valves  442  and  462 . The check valve shown in FIGS. 6A and 6B has a hinged thin plate or diaphragm mounted substantially perpendicular to the axis of the tube and configured to open only in the rightward direction. As shown in FIG. 6A, the check valve allows the liquid coolant to flow only in the rightward direction in which the thin plate opens. However, as shown in FIG. 6B, the check valve prevents the liquid coolant from flowing backward in the direction in which the thin plate closes.  
         [0037]    [0037]FIGS. 7A and 7B show the structure and operation of a further known check valve that can be used as the check valves  442  and  462 . The check valve shown in FIGS. 7A and 7B includes a spherical member or ball entrapped in a space between left- and right-side tubes. The left-side tube has a circular end that is cut flat, while the right-side tube has a notched circular end. As shown in FIG. 7A, the check valve allows the liquid coolant to flow only in the rightward direction, in which the ball is brought into contact with the notched end. However, as shown in FIG. 7B, the check valve prevents the liquid coolant from flowing backward in the direction, in which the ball is brought into contact with the circular end.  
         [0038]    [0038]FIG. 8 shows a partially cutaway top plan view illustrating the display housing  20  and the main unit housing  30 , in accordance with another embodiment of the invention, when the display housing  20  is opened so that the display surface of the display housing  20  makes an angle of 180 degrees with the manual operation surface of the main unit housing  30  in the electronic apparatus  10  of FIG. 1. The display housing  20  has a construction similar to that shown in FIG. 2, and hence will not be described again.  
         [0039]    In FIG. 8, the main unit housing  30  contains therein: a heat absorbing member  340  which is placed in close proximity to the heat generating portion  300 ; check valves  444  and  464  which allow the liquid coolant to flow in only one direction; and an elastomer bag  414  which is connected between the check valves  444  and  464 . The heat absorbing member  340 , the check valves  444  and  464 , and the elastomer bag  414  are located behind the manual operation surface on the side of the keyboard  32 . In FIG. 8, the elastomer bag  414  is located behind the aluminum bottom plate of the keyboard  32  and the pointing device  34 . For simplicity of illustration, the support plate  421  (FIG. 2) for the elastomer bag  414  is not shown in FIG. 8.  
         [0040]    The outlet port of the heat dissipating member  220  is connected to the inlet port of the heat absorbing member  340  via a rubber tube  222  and a tube  322 . The outlet port of the heat absorbing member  340  is connected to the inlet port of the check valve  444  via a tube  324 . The outlet port of the check valve  444  is connected to the inlet port of the elastomer bag  414  via a tube  344 . The outlet port of the elastomer bag  414  is connected to the inlet port of the check valve  464  via a tube  364 . The outlet port of the check valve  464  is connected to the inlet port of the heat dissipating member  221  via a tube  330  and a rubber tube  224 . The closed loop fluid circuit is thus formed.  
         [0041]    In operation, when the user operates the keyboard  32  and the pointing device  34 , the elastomer bag  414 , in response to the pressing and vibration associated with the operation, compresses and expands in a repetitive manner and thus pumps the liquid coolant contained therein. With the elastomer bag  414  repetitively compressing, the liquid coolant contained therein is pumped through the check valve  464  and gradually flows into the heat dissipating member  221  where the heat is dissipated. After that, the liquid coolant flows into the accumulator tank  210 . With the elastomer bag  414  repetitively expanding, the liquid coolant in the tank  210  flows out and is cooled through the heat dissipating member  220 , and then flows into the heat absorbing member  340  where the liquid coolant absorbs heat from the heat generating portion  300 . After that, the liquid coolant is passed through the check valve  444  and gradually flows back into the elastomer bag  414 . In this way, the liquid coolant circulates between the heat absorbing member  340  and the heat dissipating members  220  and  221 .  
         [0042]    [0042]FIG. 9 shows a partially cutaway top plan view illustrating the display housing  20  and the main unit housing  30 , in accordance with a further embodiment of the invention, when the display housing  20  is opened so that the display surface of the display housing  20  makes an angle of 180 degrees with the manual operation surface of the main unit housing  30  in the electronic apparatus  10  of FIG. 1. The display housing  20  has a construction similar to that shown in FIG. 2, and hence will not be described again.  
         [0043]    In FIG. 9, the main unit housing  30  contains therein: a heat absorbing member  340  placed in close proximity to the heat generating portion  300 ; check valves  446  and  466  which allow the liquid coolant to flow in only one direction; and an elastomer bag  416  connected between the check valves  446  and  466 . The heat absorbing member  340 , check valves  446  and  466 , and elastomer bag  416  are located behind the manual operation surface on the side of the keyboard  32 . In FIG. 9, the elastomer bag  416  is located behind the speaker  38  and the jog dial  42 . In addition, the elastomer bag  416  is located above the cooling fan  46  and the CD/DVD drive  40 . Further, the elastomer bag  416  may be placed above the hard disk drive  48 .  
         [0044]    Each of the cooling fan  46 , the CD/DVD drive  40 , and the hard disk drive  48  generates vibration due to the eccentricity of its axis of rotation, during its operation. The speaker  38  vibrates when producing sound. The elastomer bag  416  has the effect of absorbing the vibration of the cooling fan  46 , CD/DVD drive  40 , and hard disk drive  48  and thus reducing the noise while also reducing the vibration to be transmitted to other components contained in the electronic apparatus  10 . The elastomer bag  416  can also absorb the heat generated by the cooling fan  46 , CD/DVD drive  40 , and hard disk drive  48 .  
         [0045]    The outlet port of the heat dissipating member  220  is connected to the inlet port of the heat absorbing member  340  via a rubber tube  222  and a tube  322 . The outlet port of the heat absorbing member  340  is connected to the inlet port of the check valve  446  via a tube  324 . The outlet port of the check valve  446  is connected to the inlet port of the elastomer bag  416  via a tube  346 . The outlet port of the elastomer bag  416  is connected to the inlet port of the check valve  466  via a tube  366 . The outlet port of the check valve  466  is connected to the inlet port of the heat dissipating member  221  via a tube  330  and a rubber tube  224 . The closed loop fluid circuit is thus formed.  
         [0046]    In operation, when the speaker  38  produces sound, or when the user operates the jog dial  42 , or when the CD/DVD drive  40 , the cooling fan  46  or the hard disk drive  48  is in operation, the elastomer bag  416 , in response to the pressing and vibration associated with the operation or vibration, compresses and expands in a repetitive manner and thus pumps the liquid coolant contained therein. With the elastomer bag  416  repetitively compressing, the liquid coolant contained therein is pumped through the check valve  466  and flows into the heat dissipating member  221  where the heat is dissipated. After that, the liquid coolant flows into the accumulator tank  210 . With the elastomer bag  416  repetitively expanding, the liquid coolant in the tank  210  flows out and is cooled through the heat dissipating member  220 , and then flows into the heat absorbing member  340  where the liquid coolant absorbs heat from the heat generating portion  300 . After that, the liquid coolant is passed through the check valve  446  and flows back into the elastomer bag  416 . In this way, the liquid coolant circulates between the heat absorbing member  340  and the heat dissipating members  220  and  221 .  
         [0047]    [0047]FIG. 10 shows a partially cutaway top plan view illustrating the display housing  20  and the main unit housing  30 , in accordance with a still further embodiment of the invention, when the display housing  20  is opened so that the display surface of the display housing  20  makes an angle of 180 degrees with the manual operation surface of the main unit housing  30  in the electronic apparatus  10  of FIG. 1. The display housing  20  has a construction similar to that shown in FIG. 2, and hence will not be described again.  
         [0048]    In FIG. 10, the main unit housing  30  contains therein: a heat absorbing member  340  which is placed in close proximity to the heat generating portion  300 ; check valves  448  and  468  which allow the liquid coolant to flow in only one direction; and an elastomer bag  418  which is connected between the check valves  448  and  468 . The heat absorbing member  340 , the check valves  448  and  468 , and the elastomer bag  418  are located behind the manual operation surface of the keyboard  32 . In FIG. 10, the battery  36  is a relatively heavy component, and is placed close to and along the elastomer bag  418  disposed as shown in FIG. 3B. More specifically, the battery  36  is supported, for example, on sponge-like cushioning members  362  and accommodated in the main unit housing  30  in such a manner as to be movable relative to the elastomer bag  418 .  
         [0049]    The outlet port of the heat dissipating member  220  is connected to the inlet port of the heat absorbing member  340  via a rubber tube  222  and a tube  322 . The outlet port of the heat absorbing member  340  is connected to the inlet port of the check valve  448  via a tube  324 . The outlet port of the check valve  448  is connected to the inlet port of the elastomer bag  418  via a tube  348 . The outlet port of the elastomer bag  418  is connected to the inlet port of the check valve  468  via a tube  368 . The outlet port of the check valve  468  is connected to the inlet port of the heat dissipating member  221  via a tube  330  and a rubber tube  224 . The closed loop fluid circuit is thus formed.  
         [0050]    In operation, when the electronic apparatus  10  is carried by a user, for example, in a moving train, the electronic apparatus  10  is subjected to the vibration of the train, and the battery  36  vibrates in the main unit housing  30  within the elastic limit of the cushioning members  362 . When the battery  36  vibrates, the elastomer bag  418 , in response to the vibration, compresses and expands in a repetitive manner and thus pumps the liquid coolant contained therein. With the elastomer bag  418  repetitively compressing, the liquid coolant contained therein is pumped through the check valve  468  and gradually flows into the heat dissipating member  221  where the heat is dissipated. After that, the liquid coolant flows into the accumulator tank  210 . With the elastomer bag  418  repetitively expanding, the liquid coolant in the accumulator tank  210  flows out and is cooled through the heat dissipating member  220 , and then flows into the heat absorbing member  340  where the liquid coolant absorbs heat from the heat generating portion  300 . After that, the liquid coolant is passed through the check valve  448  and gradually flows back into the elastomer bag  418 . In this way, the liquid coolant circulates between the heat absorbing member  340  and the heat dissipating members  220  and  221  while the electronic apparatus  10  is being operated in the moving train.  
         [0051]    [0051]FIG. 11 shows a partially cutaway top plan view illustrating the display housing  20  and the main unit housing  30 , in accordance with a still further embodiment of the invention, when the display housing  20  is opened so that the display surface of the display housing  20  makes an angle of 180 degrees with the manual operation surface of the main unit housing  30  in the electronic apparatus  10  of FIG. 1.  
         [0052]    In FIG. 11, the display housing  20  contains therein: heat dissipating members  220  and  221 , through which the liquid coolant flows; an accumulator tank  210  which is connected between the dissipating members  220  and  221  and used to store the cooling liquid; an elastomer bag  420 ; and check valves  450  and  470 . The elastomer bag is disposed in close proximity to the rear side of the display  22 . The heat dissipating members  220  and  221 , accumulator tank  210 , and check valves  450  and  470  are placed behind the display  22 . The display  22  is a relatively heavy component, and is supported in the display housing  20  via a sponge-like cushioning member  23  in such a manner as to be movable in a direction perpendicular to the display surface, that is, toward and away from the elastomer bag  420 , when subjected to vibration. For simplicity of illustration, the support plate  421  (FIG. 2) for the elastomer bag  414  is not shown in FIG. 11.  
         [0053]    The main unit housing  30  contains therein a heat absorbing member  340  which is located behind the surface of the keyboard  32  and placed in close proximity to the heat generating portion  300 .  
         [0054]    The outlet port of the heat dissipating member  220  is connected to the inlet port of the check valve  450  via a tube  333 . The outlet port of the check valve  450  is connected to the inlet port of the elastomer bag  420  via a tube  350 . The outlet port of the elastomer bag  420  is connected to the inlet port of the check valve  470  via a tube  360 . The outlet port of the check valve  470  is connected to the inlet port of the heat absorbing member  340  via a tube  331  and a rubber tube  222 . The outlet port of the heat absorbing member  340  is connected to the inlet port of the heat dissipating member  221  via a tube  325  indicated by a dashed line and via a rubber tube  224 . The outlet port of the heat dissipating member  221  is connected to the inlet port of the accumulator tank  210 . The outlet port of the accumulator tank  210  is connected to the inlet port of the heat dissipating member  220 . The closed loop fluid circuit is thus formed. In this way, the liquid coolant circulates between the heat absorbing member  340  and the heat dissipating members  220  and  221  without consuming energy or power in the electronic apparatus  10 .  
         [0055]    In operation, when the electronic apparatus  10  is operated, for example, in a moving train, the electronic apparatus  10  is subjected to the vibration of the train, and the display  22  vibrates in the display housing  20  within the elastic limit of the cushioning member  23 . When the display  22  vibrates, the elastomer bag  420 , in response to the vibration, compresses and expands in a repetitive manner and thus pumps the liquid coolant contained therein. With the elastomer bag  420  repetitively compressing, the liquid coolant contained therein is pumped through the check valve  470  and flows into the heat absorbing member  340  where the liquid coolant absorbs heat from the heat generating portion  300 . The liquid coolant then flows into the heat dissipating member  221  where the heat is dissipated. After that, the liquid coolant gradually flows into the accumulator tank  210 . With the elastomer bag  420  repetitively expanding, the liquid coolant in the tank  210  flows out and is cooled through the heat dissipating member  220 , is then passed through the check valve  450 , and gradually flows back into the elastomer bag  420 . In this way, the liquid coolant circulates between the heat absorbing member  340  and the heat dissipating members  220  and  221 .  
         [0056]    Alternatively, similarly to the configuration shown in FIG. 10, the outlet port of the heat absorbing member  340  may be connected to the inlet port of the check valve  448  via the tube  324  indicated by a semi-dashed line; the outlet port of the check valve  448  may be connected to the inlet port of the elastomer bag  418  via the tube  348 ; the outlet port of the elastomer bag  418  may be connected to the inlet port of the check valve  468  via the tube  368 ; and the outlet port of the check valve  468  may be connected to the rubber tube  224  via the tube  330 .  
         [0057]    In this case, the arrangement consisting of the check valve  450 , elastomer bag  420  and check valve  470  is connected in series with the arrangement consisting of the check valve  448 , elastomer bag  418  and check valve  468 , and the liquid coolant circulates between the heat absorbing member  340  and the heat dissipating members  220  and  221 . If the elastomer bags  418  and  420  are each provided with a moderate restoring force, the elastomer bags  418  and  420  can alternately be caused to expand and compress, and therefore, the air bag  212  in the accumulator tank  210  may be eliminated or reduced in size.  
         [0058]    [0058]FIG. 12 shows a partially cutaway top plan view illustrating the display housing  20  and the main unit housing  30 , in accordance with a still further embodiment of the invention, when the display housing  20  is opened so that the display surface of the display housing  20  makes an angle of 180 degrees with the manual operation surface of the main unit housing  30  in the electronic apparatus  10  of FIG. 1. The display housing  20  and the main unit housing  30  have constructions similar to those shown in FIG. 10, except that a liquid fuel such as methanol is used as the liquid coolant, that the main unit housing  30  further includes a fuel cell  218 , and that the accumulator tank  210  stores the liquid fuel for the fuel cell  218 . In this case, there is no need to provide a liquid coolant storage tank separately from the liquid fuel storage tank. The fuel cell  218  consumes the liquid fuel in the accumulator tank  210  as the electronic apparatus  10  is operated, and the liquid fuel in the accumulator tank  210  gradually decreases. It is desirable to replenish the liquid fuel before it is depleted. In other respects, the operation of each component in FIG. 12 is the same as that of the corresponding component in FIG. 10.  
         [0059]    [0059]FIG. 13 shows a combination of a pump element consisting of the series connection of the check valve  442 , elastomer bag  412  and check valve  462  shown in FIG. 2, a pump element consisting of the series connection of the check valve  444 , elastomer bag  414  and check valve  464  shown in FIG. 8, a pump element consisting of the series connection of the check valve  446 , elastomer bag  416  and check valve  466  shown in FIG. 9, and a pump element consisting of the series connection of the check valve  448 , elastomer bag  418  and check valve  468  shown in FIG. 10. The respective pump elements are connected in parallel through branch tubes  324  and  330 . Such a combination serves to further promote the circulation of the liquid coolant between the heat absorbing member  340  and the heat dissipating members  220  and  221 .  
         [0060]    In each of the embodiments shown in FIGS.  2  and  8  to  13 , alternatively, the check valves may be arranged so as to flow the liquid coolant in the direction opposite to the illustrated direction. In this case, the liquid coolant is caused to flow in the opposite direction.  
         [0061]    The above-described embodiments are only typical examples, and their modifications and variations are apparent to those skilled in the art. It should be noted that those skilled in the art can make various modifications to the above-described embodiments without departing from the principle of the invention and the accompanying claims.