Patent Publication Number: US-2006018775-A1

Title: Liquid circulation system and liquid cooling system therewith

Description:
INCORPORATION BY REFERENCE  
      The present application claims priority from Japanese application JP2004-214574 filed on Jul. 22, 2004, the content of which is hereby incorporated by reference into this application.  
     BACKGROUND OF THE INVENTION  
      The invention relates to a liquid circulation system for circulating liquid using a pump and a liquid cooling system therewith, and more particularly to a liquid circulation system equipped with a pump capable of being miniaturized and a mounting structure thereof, and a liquid cooling system therewith.  
     PRIOR ART  
      The increasing speed of a device and an integrated circuit used in a personal computer, a server or the like, especially a CPU has been recently much-needed, which has been increasing heating value.  
      The present mainstream of cooling a CPU is a direct air-cooling system for spraying cooling air to a heat sink by fixing the heat sink on the CPU and mounting a fan on it. However, cooling by means of the direct air-cooling system restricts a space around the CPU due to high-density conversion of an apparatus, as well as the size of the heat sink, thus restricting cooling capacity and fan size. To obtain high air volume, this needs to rotate a small-sized fan at a high speed, which leads to increasing noise.  
      For utilization of a large-sized heat sink and a large-sized fan with high efficiency, attempts have been made to apply a heat transport system such as a liquid cooling system. However, the conventional liquid cooling system is constituted of a larger amount of parts than an air cooling system, which causes difficult miniaturization and needs reduction in the number of parts and size.  
      As a related art capable of miniaturizing the liquid cooling system, for example, an art disclosed in JP-A-2004-92610 is known. This related art relates to miniaturization of a pump and uses a small-sized impeller.  
      As another related art, for example, an art disclosed in JP-A-2003-343492 is known. This related art, a centrifugal pump being slimmed, constitutes a pump from a slim impeller and a small-sized port.  
      As a further related art, an art disclosed in JP-A-2004-47921, which miniaturizes a liquid cooling system by integrating a pump with a cooling jacket, is used.  
     SUMMARY OF THE INVENTION  
      The foregoing related art disclosed in JP-A-2004-92610 has a problem that a small-sized impeller cannot increase a flow rate because efficiency is lower than that of a large-sized impeller. In the foregoing related art disclosed in JP-A-2003-343492, its centrifugal pump has a characteristic that its open flow rate is higher and static pressure is lower than that of one of other systems, for example, a piston pump. The related art using a small-diameter port has a problem that the flow rate of coolant becomes lower, especially in using coolant with high viscosity. Moreover, the art disclosed in JP-A-2004-47921 has a problem that the shape of a pump case must be specialized in accordance with the shape of an object to be cooled because part of a pump casing becomes a heat receiving surface, which leads to lost general versatility of a pump itself and difficult cost reduction by mass-production effect.  
      Any of the respective related arts relates to a liquid cooling system using a centrifugal pump. One of fundamental problems of the centrifugal pumps is that a liquid flow stops when air is mixed into an internal pump. The liquid flow stop is more apt to occur due to air mixing as the space of the internal pump is smaller.  
      A conventional liquid cooling system aimed at free maintenance has a problem of the permeability of coolant from a pump surface, namely, that coolant is lost while passing through a material constituting a pump case. This problem can be solved by using metal for a pump casing. However, if an impeller must be driven by magnetic force, metal cannot be, in practice, used for the case and polymer material is unavoidably used. A portion which is hardly associated with the magnetic force can use metal, which causes a problem that a cost increase occurs.  
      Accordingly, it is an object of the present invention to provide a liquid circulation system for circulating liquid using a pump and a liquid cooling system therewith, capable of solving the foregoing problems of conventional arts and the foregoing problem a centrifugal pump has, reducing the number of parts, and being miniaturized.  
      To achieve the aforementioned object, a liquid circulation system of the present invention, circulating liquid with a pump equipped with an impeller having a plurality of vanes, is structured as follows: the pump is installed through a liquid sealing mechanism on an opening section formed in a wall for a component in a liquid circulation passage so that the impeller in the pump may be disposed inside the component, a partition plate formed with a hole at such a position as to face the center of the impeller, a port is formed between a wall surface having the opening section and the partition plate, thereby generating a liquid flow in the direction of the port through the hole from the inside of the component by the rotation of the impeller.  
      In the foregoing structure, the pump equipped with the impeller comprises a shaft inserting through the center of the rotating shaft of the impeller, a wall for vertically supporting the shaft, permanent magnets mounted on the impeller, and electromagnets, which are respectively fitted on a surface on the opposite side to the impeller, sandwiching the wall to drive the rotation of the impeller.  
      The aforementioned object can be achieved by using the foregoing liquid circulating system in addition to a liquid cooling system having a component for performing heat exchange, a component for holding coolant, and a component which is brought into contact with a heat generating member and cools the heat generating member.  
      Accordingly, the present invention can miniaturize a liquid circulation system and minimize pressure drop loss in piping.  
      Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view illustrating an example of a configuration of an electronic device to which a liquid cooling system is applied according to an embodiment of the present invention;  
       FIG. 2  is a sectional view illustrating a configuration of a pump section used according to one embodiment of the present invention;  
       FIG. 3  is an explanatory view illustrating shapes of an impeller and vanes constituting a pump section, arrangement of electromagnets, and arrangement of permanent magnets;  
       FIG. 4  is a sectional view illustrating a configuration of a liquid cooling system according to a first embodiment of the present invention;  
       FIG. 5  is a sectional view illustrating a configuration of a liquid cooling system according to a second embodiment;  
       FIG. 6  is a sectional view illustrating a configuration of a liquid cooling system according to a third embodiment; and  
       FIG. 7  is a sectional view illustrating another configuration of a pump section used according to an embodiment of the present invention. 
    
    
      Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. However, this does not limit the present invention.  
     PREFERRED EMBODIMENTS OF THE INVENTION  
     First Embodiment  
       FIG. 1  is a perspective view illustrating an example of a configuration of an electronic device to which a liquid cooling system is applied according to an embodiment of the present invention, where a reference symbol  101  is a casing, a reference symbol  102  is a mother board, a reference symbol  103  is a CPU, a reference symbol  104  is a chip set, a reference symbol  105  is a memory, a reference symbol  106  is a PCI board, a reference symbol  107  is a HDD, a reference symbol  108  is a CD-ROM, a reference symbol  109  is FDD, a reference symbol  110  is a power supply unit, reference symbols  111   a,    111   b  are jackets, a reference symbol  112  is a radiator, a reference symbol  113  is a tank section, a reference symbol  114  is a pump section, a reference symbol  115  is a fan, and reference symbols  116  to  118  are tubes. The electronic device illustrated in  FIG. 1  is an approx. 44.4 high slim server, that is, a 1U server as an example.  
      The server as the electronic device illustrated in  FIG. 1  is constituted by mounting the CPU  103 , the chip set  104 , the memory  105 , and the PCI board  106  on the mother board  102  provided inside the casing  101 . As an external storage, the HDD  107 , the CD-ROM  108 , and the FDD  109  are mounted ahead, and the power supply unit  110  is mounted on the rear side of the casing  101 .  
      The liquid cooling system provided on the server is constituted of the radiator  112  fitted with the fan  115 , the tank section  113  provided at its one end, the pump section  114  provided at the other end, jackets  111   a ,  111   b  mounted on the two CPUs  103 , the tube  118  for making a connection between the jackets, the tube  116  for connecting the jacket  111   b  with the tank section  113 , the tube  117  for connecting the jacket  111   a  with the pump section  114 , and coolant circulating inside the tube  117 . As the coolant, it is sufficient to use a mixture of ethylene glycol or propylene glycol and water. A mixture prepared by mixing ethylene glycol or propylene glycol with water at the rate of approx. 30% to water may be used.  
      The jackets  111   a  and  111   b  of the liquid cooling system are respectively mounted on the CPUs  103  and absorb heat from the CPUs  103 . Specifically, the jackets  111   a ,  111   b  are formed out of metal with high heat transfer such as copper or aluminum. Contact surfaces between the jackets  111   a ,  111   b  and the CPU  103  are crimped with thermal compound, silicon rubber with high heat transfer or the like sandwiched therebetween so that the heat generated by the CPU  103  may be transferred to the jacket with high efficiency. The coolant passes through the inside of each of the jackets  111   a ,  111   b , and heat from the CPU  103  is transferred to the coolant and carried to the radiator  112 .  
      The radiator  112  for cooling coolant is provided with the tank section  113  for storing coolant and the pump section  114  for generating a liquid flow. The configuration of the radiator  112  having the pump section  114  is described below. The radiator  112  is attached with the fan  115 , and wind is sent to the radiator  112 .  
      As described earlier, piping of the liquid cooling system is formed out of the tubes  116  to  118 . The tube  116  connects the jacket  111   b  with the tank section  113 , the tube  117  connects the pump section  114  with the jacket  111   a , and the tube  118  connects the jacket  111   a  with the jacket  111   b.    
      The order of a coolant flow according to this embodiment is as follows: pump section  114 →jacket  111   a →jacket  111   b →tank section  113 →radiator  112 →pump section  114  (again). By passing the coolant cooled by the radiator  112  through the pump section  114  in this way, the pump section  114  can be prevented from being overheated.  
       FIG. 2  is a sectional view illustrating a configuration of a pump section  114  in  FIG. 1 ,  FIG. 3  is an explanatory view illustrating shapes of an impeller and vanes constituting a pump section  114 , arrangement of electromagnets, and arrangement of permanent magnets, and  FIG. 4  is a sectional view illustrating a configuration of a liquid cooling system according to an embodiment. The liquid cooling system illustrated in  FIG. 4  is constituted by installing the pump section  114  on the radiator  112 . FIGS.  2  to  4 , a reference symbol  201  is an impeller, a reference symbol  202  is a permanent magnet, a reference symbol  203  is a vane, a reference symbol  204  is a bearing, a reference symbol  205  is a shaft, a reference symbol  206  is a washer, a reference symbol  207  is a bottom wall, a reference symbol  208  is a stopper, a reference symbol  209  is a bent section, a reference symbol  210  is a packing, a reference symbol  211  is an electromagnet, a reference symbol  301  is a passage, a reference symbol  302  is a fin, a reference symbol  303  is a wall surface, a reference symbol  304  is a hole, a reference symbol  305  is a partition plate, a reference symbol  306  is a port and a reference symbol  307  is a screw, and other symbols are the same as in  FIG. 1 .  
      The pump section  114  is constituted as a centrifugal pump formed integrally with a motor and, as illustrated in  FIG. 2 , the pump section  114  consists of the impeller  201  having the permanent magnets  202  and the vane  203 , the bottom wall  207  for supporting the impeller  201 , and the electromagnets  211  mounted on the bottom wall  207 . The impeller  201  includes a plurality of permanent magnets  202  as illustrated in  FIG. 3  ( a ) and  FIG. 3  ( c ), and the plurality of vanes  203 . The bearing  204  is in the center of the impeller  201 , and the shaft  205  penetrates through the bearing  204 . The shaft  205  which penetrates through the inside of the bearing  204  is formed with the two washers  206  at the top and bottom thereof. The bottom washer  206  has a notched shape and is embedded to be fixed in the bottom wall  207 . On the other hand, the top washer  206  is constituted so as not to be rotated by the bent section  209  of the stopper  208 .  
      The bearing  204 , the shaft  205 , and the washer  206  may be formed out of a material with excellent wear resistance, such as ceramic. The bearing  204  is set so as to be brought into contact with the top and bottom washers  206 , therefore contact surfaces thereof rub with each other while the impeller  201  is rotating, however, these parts have excellent wear resistance, thus exhibiting long service life.  
      On the bottom wall  207  supporting the shaft, the packing  210  is provided at a surface on the same side as the surface on which the impeller  201  is installed, and electromagnets  211  are provided at the opposite surface. A motor for driving the rotation of the impeller  201  is formed out of the electromagnets  211  provided on the bottom plate  207  and the permanents magnets  202  provided on the impeller  201 . The electromagnets  211  provided on the bottom plate  207 , as illustrated in  FIG. 3  ( b ), is constituted of a plurality of coils producing a magnetic force in such a direction as to vertically penetrate through the bottom wall  207 , and the permanents magnets  202  provided on the impeller  201  similarly, as shown in  FIG. 3  ( c ), is a plurality of permanents magnets for generating magnetic forces in a direction perpendicular to the bottom wall  207 , where the adjacent magnets are arranged so as to have reversed polarity each other.  
      The motor for rotating the impeller  201  is constituted of the permanent magnets  202  facing through the bottom plate  207  and the electromagnets  211 , therefore the bottom plate  207  requires use of a member made of a material capable of penetrating a magnetic force, and it may be formed out of hard plastic or the like.  
      The pump section  114  does not have a port or a casing for ensuring water tightness, which a conventional pump uses. The pump section  114 , being not used solely with only a structure illustrated in  FIG. 2 , can exhibit a function serving as a pump only by being installed other radiator, tank or the like. Referring now to  FIG. 4 , there is described an example of a configuration in which the pump section  114  illustrated in  FIG. 2  is installed on the radiator  112 . An arrow indicated in  FIG. 4  shows a flow of coolant.  
      The radiator  112  is constituted of piping forming a plurality of passages  301  and a great number of fins  302  mounted thereon. On the left and right thereof, the tank section  113  and the pump section  114  are installed, and each of them is connected with the passages  301 . The plurality of passages  301  are parallel, and the fins  302  are thermally jointed to the passages  301 , so that the heat of the coolant running through the passages  301  is transmitted to the fins  302 . The passages  301  and the fins  302  are formed so that the wind from the fan  115  may hit, where the heat of the coolant is cooled. The radiator section  112  is formed out of copper or aluminum with high thermal conductivity.  
      The tank section  113  stores a fixed amount of coolant to ensure long-term reliability of the liquid cooling system. The liquid cooling system includes some portions using a member causing water permeation such as a polymer member, from which water permeation occurs, thus gradually reducing liquid amount. The tank section generally requires to maintain a sufficient amount of liquid for endurance against long-term use, however, this embodiment requires a smaller amount of polymer material usage, thus causing reduction in water permeation amount. Therefore, a smaller-size tank than a conventional one may be used.  
      The side on which the pump section  114  of the radiator  112  is installed is constituted of the wall surface  303  with the hole, in which the pump section  114  is assembled. The vanes  203  of the pump section  114  are positioned on the inner side of the wall surface  303 . The pump section  114  is fixed on the wall surface  303  by a screw  307 . Between the wall surface  303  and the bottom wall  207  of the pump section  114 , the packing  210  exists, thus causing no liquid leakage. On the inside of the wall surface  303  with holes of the radiator  112 , there is provided a partition plate  305  with the hole  304  at a position approaching the impeller  201  of the pump section  114  installed on the wall surface  303  without contacting the impeller  201 . The hole  304  is formed so as to face the central portion of the impeller  201 . On the passage  301  side of the hole  304 , a room for guiding coolant collected from the plurality of passages  301  to the hole  304 . The port  306  is provided on the impeller side of the space partitioned by the partition plate  305 , that is, between the partition plate  305  and the wall surface  303 .  
      With the foregoing configuration, by driving the rotation of the impeller, the coolant passing through the passage  301  of the radiator  112  is sucked from the hole  304  formed on the partition plate  305  and flows out of the port  306 . The pump section  114  operates under a state assembled in the radiator  112  and can eliminate piping for connecting the pump section with the radiator, thus miniaturizing the liquid cooling system and further eliminating pressure loss due to piping. Specifically, a portion sucking liquid by negative pressure resulting from the rotation of the vanes  203  of the impeller  201  is the hole  304  on the partition plate  305 . The hole  304 , having no restrictions on its diameter, can be significantly enlarged, thus almost neglecting pressure loss.  
      In a conventional way, the pump section and the tank are structured so as to be connected with each other through piping. If large-diameter piping is used, a pump port itself is enlarged, thus upsizing the pump. If the pump needs downsizing, the port must be unavoidably reduced in diameter, thus causing lowering of flow rate due to pressure loss.  
      In a conventional way, water permeation occurs from the whole pump casing, while the pump section  114  according to this embodiment is half immersed in the metallic radiator  112 , therefore water permeation from the pump section  114  is limited to only a surface of the bottom wall  207 . The bottom wall  207  has a surface area not larger than the half of a conventional pump casing, thus achieving water permeation amount not larger than the half of a conventional one.  
      This embodiment can use the hole on the wall surface  303  installed with the pump section  114  as those for filling the liquid cooling system with liquid, and the pump section  114  as its lid. The hole on the wall surface  303  can facilitate filling with liquid because the hole is much larger in diameter than piping.  
      In this embodiment, a case where the tank section  113  is installed on the radiator  112  is described, however, the present invention may individually constitute the tank section  113  as the radiator  112  for connection with piping.  
     Second Embodiment  
       FIG. 5  is a sectional view illustrating a configuration of a liquid cooling system according to a second embodiment. Referring now to  FIG. 5 , the liquid cooling system according to this embodiment is described below. The liquid cooling system illustrated in  FIG. 5  is constructed by installing a pump section on an independent tank section. In  FIG. 5 , a reference symbol  401  is a tank, reference symbols  402 ,  403  are ports, a reference symbol  404  is a wall surface, a reference symbol  405  is a hole, and a reference symbol  406  is a partition plate. Other symbols are the same as in FIGS.  1  to  4 . An arrow indicated in  FIG. 5  shows a flow of coolant.  
      In  FIG. 5 , the tank  401  is made of metal, the bottom surface of the tank  401  has the holed wall surface  404  for mounting the pump section  114  thereon, where the pump section  114  is assembled. The vanes  203  of the pump section  114  are positioned inside the wall surface  404 . The pump section  114  is fixed on the wall surface  404  by the screw  307 . Between the wall surface  404  and the bottom wall  207  of the pump section  114 , the packing  210  is intervened, which prevents liquid from leaking. Inside the holed wall surface  404  of the tank  401 , the partition plate  406  with the hole  405  is provided at a such a close position as to come into no contact with the impeller  201  of the pump section  114  installed on the wall surface  404 . The hole  405  is formed so as to face the central portion of the impeller  201 , and is open directly to the coolant in the tank. On the impeller side of a space partitioned by the partition plate  406 , that is, between the partition plate  406  and the wall surface  404 , the outlet port  403  for coolant is formed and, on the top of the tank  401 , the inlet port  402  for coolant is formed.  
      With the foregoing configuration, when the rotation of the impeller  201  is driven, the coolant in the tank  401  is sucked from the hole  405  formed on the partition plate  406  and flows out of the outlet port  403 . The pump section  114  operates in such a state as to be assembled in the tank  401 , so that piping for connecting the pump section  114  with the tank  401  can be eliminated, thus achieving miniaturization of the liquid cooling system. Moreover, pressure loss due to piping can be also eliminated. Specifically, a portion which sucks liquid with negative pressure generated by the rotation of the vanes  203  of the impeller  201  is the hole  405  of the partition plate  406 . The diameter of the hole  406 , having no restrictions, can be set so as to be significantly large, thus setting pressure loss to a roughly negligible degree.  
      The coolant from the outlet port  403  flows in the order of the jacket and radiator and returns to the tank  401  from the inlet port  402 , which are not shown in  FIG. 5 .  
      In a conventional way, the pump section and the tank are structured so as to be connected with each other through piping. If large-diameter piping is used, a pump port itself is enlarged, thus upsizing the pump. If the pump needs downsizing, the port must be unavoidably reduced in diameter, thus causing lowering of flow rate due to pressure loss.  
      In the conventional way, water permeation occurs at the whole pump casing. On the other hand, the pump section  114  according to this embodiment, being half submerged in the metallic tank  401 , water permeation from the pump section  114  is restricted to only the surface of the bottom wall  207 . The bottom wall  207 , having a surface area not larger than a half as many as a conventional pump casing, can restrain water permeation to not larger than a half.  
      The hole on the wall surface  404  of the tank  401  installed with the pump section  114  can be used as a hole for filling the liquid cooling system with liquid, and the pump section  114  can be used as a lid. The hole on the wall surface  404  is far larger in diameter than piping, which can facilitate filling with liquid.  
      Moreover, a centrifugal pump generally has a problem of a liquid flow being stopped at the time of air mixing, which requires to discharge air at air mixing, but the conventional liquid cooling system, having high pressure loss because of piping connection, requires additional means of discharging air in the pump.  
      However, this embodiment can facilitate discharge of air in a pump. In other words, in the embodiment of the present invention illustrated in  FIG. 5 , if air gathers in the pump  114 , that is, if air gathers around the vanes  203  of the impeller  201  surrounded by the partition plate  406  and the wall surface  404 , it is sufficient only to stop the operation of the pump section  114 , by which the air leaks upwards through the hole  405 . In this way, this embodiment can facilitate discharge of air in the pump.  
      Stopping of a liquid flow occurs if air gathers around the vanes  203  of the impeller  201  and liquid amount in the space reduces. With this embodiment, a volume surrounding the vanes  203  of the impeller  201 , that is, a space around the vanes  203  of the impeller  201  surrounded by the partition plate  406  inside the tank  401  is part of the tank  401 , however, the size of the tank is generally larger than that of the pump, and this volume, namely, liquid amount is more than that of a conventional pump, therefore, the effect of air mixing is relieved, thus making it difficult to generate stopping of a liquid flow.  
     Third Embodiment  
       FIG. 6  is a sectional view illustrating a configuration of a liquid cooling system according to a third embodiment. Referring to the drawing, a liquid cooling system according to this embodiment is described. The liquid cooling system illustrated in  FIG. 6  is constituted by integrating the pump section with a radiator. In  FIG. 6 , a reference symbol  501  is a jacket, reference symbols  502 ,  503  are ports, a reference symbol  504  is a wall surface, a reference symbol  505  is a hole, a reference symbol  506  is a duct, a reference symbol  507  is an opening section, and a reference symbol  508  is a heat sink. Other symbols are the same as in  FIGS. 1 and 2 . An arrow indicated in  FIG. 6  shows a flow of coolant.  
      In  FIG. 6 , the jacket  501  is formed out of metal with excellent thermal conductivity, such as copper or aluminum. Onto the bottom surface of the jacket  501 , a heat generating body to be cooled such as a CPU is jointed through thermal conductivity grease or the like. On the side of the jacket  501 , there are provided an inlet port  502  and an outlet port  503  for coolant. Moreover, a top surface  504  is formed with the hole  505 . In the hole  505  on the top surface  504 , the pump section  114  is assembled, and the vanes  203  of an impeller are put inside the jacket. Although not illustrated, like other embodiments, the pump section  114  is fixed by screwing, and a packing is provided between the top surface  504  and the pump section  114 , thus preventing liquid leakage from between the jacket  501  and the pump section  114 .  
      The duct  506  is provided inside the jacket  501 . The duct  506  is part of covered so as to include the pin-shaped heat sink  508  in a grid pattern. The duct  506  is connected with the inlet port  502  and is formed with the opening section  507 . The opening section  507  is formed so as to face the central portion of the vane  203  of the impeller  201 . That is, the duct  506  functions as piping from the inlet port  502  to the central portion of the vane  203  of the impeller  201 . Therefore, when the vanes  203  of the impeller  201  are rotated, its central portion is kept at a negative pressure, so that the inlet port  502  functions as a suction opening. The heat sink  508  provided inside the jacket  501  is formed integrally with a surface in contact with a heat generating body, namely, the bottom surface of the jacket  501  and constituted so that the heat of the heat generating body may be transmitted. Hence, the heat transmitted to the heat sink  508  is cooled by bringing it into contact with coolant.  
      With the foregoing configuration, the liquid cooling system formed integrally with the jacket according to this embodiment provides higher thermal conductivity than a conventional jacket. Detailed description is made about the liquid cooling system as follows:  
      The coolant from the port  502  is sucked into the vanes  203  of the impeller  201  from the opening section  507  through the duct  506 . Because the heat sink  508  exists in the duct  506  as well, cooling is performed to some degree at this point. The coolant passing through the vanes  203  of the impeller  201 , while being agitating by the rotation of the vanes  203  of the impeller  201 , is hurled against the heat sink  508  except a portion covered with the duct  506  and then flows out from the outlet port  503  toward the tank and the radiator not illustrated.  
      The thermal conductivity becomes higher as the flow rate of coolant is higher or coolant is more collision jet flow. In this embodiment, rotation of the vanes  203  of the impeller  201  produces a revolving liquid flow inside the jacket, so that a collision jet flow occurs, being hurled against the heat sink  508 . Therefore, a jacket constituting a cooling system illustrated in  FIG. 6  has a more rapid internal liquid flow than a conventional jacket through which coolant just passes and produces a collision jet flow, thus achieving high thermal conductivity and cooling performance.  
      In  FIG. 6 , the pump  114  operates under a state where the pump section  114  is assembled into the jacket  501 . Accordingly, piping for connecting the pump can be eliminated, thus miniaturizing the liquid cooling system.  
      In this embodiment, the shape of the heat sink  508  is like a pin-shaped fin in a grid pattern, however, the fin is not limited to this shape, but may be of any type if an area in a contact with coolant is wide.  
       FIG. 7  is a sectional view illustrating another configuration of the pump section  114 . In  FIG. 7 , a reference symbol  701  is an O-ring, and other symbols are the same as in  FIG. 2 .  
      The first to third embodiments describe that a packing is used to fill a clearance between a pump section and a component assembled with the pump section, however, as illustrated in  FIG. 7 , another way of sealing a clearance between a pump section and a component assembled with the pump section with an O-ring may be taken. A further another way, not illustrated herein, of a watertight structure by caulking may be used. Briefly speaking, it is sufficient to use a structure of filling a clearance between a pump section and a component assembled with the pump section.  
      A mounting structure of the permanent magnets  202  and the electromagnets  211  constituting the pump section  114  may be constituted, as illustrated in  FIG. 7 , by using the permanent magnets  202  of O-ring shape and embedding the electromagnets  211 . Moreover, a permanent magnet may be used for the whole impeller  201 . In short, it is sufficient to actualize a function of rotating the impeller  201 .  
      In the first to third embodiments, the features of a pump section producing a liquid flow is that the pump section consists of an impeller, a shaft, a wall vertically supporting the shaft, a wall for vertically supporting the shaft, and electromagnets positioned on a surface opposite to the impeller sandwiching the wall, and that the pump section can be constituted without need for using a port nor a casing ensuring watertightness found in a conventional pump. In addition to the foregoing features, a wall surface of a component in a liquid circulation passage has an opening section larger than the impeller size of the pump section, the pump section is assembled into the opening section, a liquid sealing structure is provided between a wall of the pump section and a wall surface of the component, and a partition plate is provided inside the component to convert the pressure generated by rotating the impeller into a liquid flow in a desired direction.  
      The pump section operates under a state assembled into a component in the liquid circulation passage, which eliminates piping for connecting a pump found in a conventional way, thus miniaturizing a liquid circulation system.  
      A partition plate as means of converting the pressure generated by rotation of the impeller into a liquid flow in a desired direction has a hole at a position corresponding to the central portion of the impeller. The hole is made to serve as a port of a suction opening of the impeller, and an outlet port is provided on the impeller side of a space partitioned by the partition plate.  
      Such a configuration can eliminate pressure loss generated between a pump section and a component of a liquid circulation system, thus increasing the flow rate of coolant. Moreover, a port formed on a partition plate of the component of the liquid circulation system is made to serve as a port for the pump section, thereby miniaturizing the liquid circulation system.  
      Furthermore, a shaft passing through the center of a rotating shaft of an impeller is equipped with a stopper, therefore even the absence of a casing around the impeller can prevent the impeller from coming off the shaft.  
      A liquid cooling system constituted by use of the liquid circulation system can perform heat transport with a liquid flow by means of the liquid circulation system. As components assembled with the pump section, a radiator, a jacket and tank are used, thus achieving miniaturization of the system and high cooling performance by flow rate increase.  
      It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.