Abstract:
A pump includes: an impeller that moves fluid; a housing section, provided adjacent to a channel for the fluid, that communicate with the channel; and a controller that positions the impeller in the channel during a driving of the impeller and houses the impeller in the housing section during a stoppage of driving of the impeller.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-62908, filed on Mar. 19, 2012, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to a pump, pump system, method of controlling a pump, and cooling system. 
       BACKGROUND 
       [0003]    Communication equipment or information processing equipment includes a cooling system that provides cooling by fluid circulation. 
         [0004]    A related technique is disclosed in Japanese Laid-open Patent Publication No. 2005-228237. 
       SUMMARY 
       [0005]    According to one aspect of the embodiments, a pump includes: an impeller that moves fluid; a housing section, provided adjacent to a channel for the fluid, that communicate with the channel; and a controller that positions the impeller in the channel during a driving of the impeller and houses the impeller in the housing section during a stoppage of driving of the impeller. 
         [0006]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0007]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1  illustrates an exemplary pump; 
           [0009]      FIG. 2  illustrates an exemplary cross section of a pump; 
           [0010]      FIG. 3  illustrates an exemplary impeller; 
           [0011]      FIG. 4  illustrates an exemplary part of a pump; 
           [0012]      FIG. 5  illustrates an exemplary part of a pump; 
           [0013]      FIG. 6  illustrates an exemplary part of a pump; 
           [0014]      FIG. 7  illustrates an exemplary positional relationship in a part of the pump; 
           [0015]      FIG. 8  illustrates an exemplary internal structure of a pump; 
           [0016]      FIG. 9  illustrates an exemplary part of the pump; 
           [0017]      FIG. 10  illustrates an exemplary motor circuit; 
           [0018]      FIG. 11  illustrates an exemplary communication apparatus; 
           [0019]      FIG. 12  illustrates an exemplary cooling system; 
           [0020]      FIG. 13  illustrates an exemplary control process; 
           [0021]      FIG. 14  illustrates an exemplary replacement of a motor; 
           [0022]      FIG. 15  illustrates an exemplary control process; 
           [0023]      FIG. 16  illustrates an exemplary processing of a control device; and 
           [0024]      FIG. 17  illustrates an exemplary transport system. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0025]    A pump that moves fluid includes a turbopump that drives an impeller. The impeller is positioned in a channel in the turbopump. Thus, if the pump comes to a stop, the impeller halting its rotation may be an obstacle to the channel and a pressure loss in the channel may be increased. 
         [0026]    For example, when a plurality of pumps are disposed in series, if one of the plurality of pumps comes to a stop, the impeller of the stopped pump may be an obstacle and hinder the running of the other pumps. For example, if a natural flow of fluid may be expected from the structure of the channel in design, the impeller of the stopped pump may be an obstacle to the natural flow. For example, a bypass that bypasses the stopped pump may be provided. Components, including a pipe and a valve for forming the bypass, may be increased, and the channel may be complicated. 
         [0027]      FIG. 1  illustrates an exemplary pump. A pump  1  illustrated in  FIG. 1  may be a turbopump that moves fluid by rotation of an impeller. For example, the pump  1  includes an impeller  20  that moves fluid. 
         [0028]    The impeller  20  is positioned inside a pump casing  30  and moves fluid with which the inside of the pump casing  30  is filled. The fluid moved by the impeller  20  may be either liquid or gas. The impeller  20  is driven by rotational power of a motor  61  in a motor casing  60  attached to the pump casing  30 , thus moving the fluid. 
         [0029]    The rotational power of the motor  61  is transmitted to the impeller  20  through magnetism produced by an electromagnet section  40  rotated by the motor  61 . For example, the impeller  20  includes a permanent magnet  24  that rotates following to magnetism of the electromagnet section  40 . The permanent magnet  24  follows to movement of the electromagnet section  40  and rotates, thereby driving the impeller  20 . 
         [0030]    A pump chamber channel  33  in which the impeller  20  is positioned when the pump  1  runs is disposed inside the pump casing  30  including the impeller  20 . The pump chamber channel  33  may form a portion of the channel for the fluid. The pump chamber channel  33  is coupled to a pipe that allows fluid to flow in the inside of the pump casing  30  to pass therethrough and to a pipe that allows fluid to flow out of the inside of the pump casing  30  to pass therethrough. 
         [0031]    A housing section  31  adjacent to and in communication with the pump chamber channel  33  is disposed inside the pump casing  30  at a location that is opposite to the electromagnet section  40  such that the pump chamber channel  33  is positioned therebetween, for example, at the location below the pump chamber channel  33  illustrated in  FIG. 1 . The housing section  31  may have a size to house the impeller  20 . 
         [0032]    A rotating shaft  32  by which the impeller  20  is rotatably supported is disposed inside the pump casing  30 . The rotating shaft  32  is positioned in a central portion inside the pump casing  30  and extends between the inside of the housing section  31 , which is positioned in a lower portion inside the pump casing  30 , and the inside of the pump chamber channel  33 , which is positioned in an upper portion inside the pump casing  30 . The lower end of the rotating shaft  32  is fixed to the bottom of the housing section  31 . The upper end of the rotating shaft  32  is fixed to the top of the pump chamber channel  33 . The rotating shaft  32  includes an outer circumferential surface  34  on which the impeller  20  is axially slideable. The impeller  20  is rotatably supported by the outer circumferential surface  34 . Thus, the impeller  20  slides along the rotating shaft  32  and may move to both the housing section  31  and the pump chamber channel  33  inside the pump casing  30 . 
         [0033]    The pump casing  30  is sealed except for the connections with the pipes attached to the outer sides of the pump casing  30 . Thus, leakage of fluid inside the pump casing  30  from portions other than the connections with the pipes is reduced. 
         [0034]    The pump  1  includes a motor circuit  50 . The motor circuit  50  may be an electric circuit that controls an electric power supplied to the motor  61  and the electromagnet section  40  and includes a power source  51  and a switch  52 . The switch  52  controls an electric power to be supplied from the power source  51  to the motor  61  and the electromagnet section  40  in accordance with a control signal input from the outside. For example, when receiving a control signal that turns on the pump  1 , the switch  52  operates so as to supply an electric power from the power source  51  to the motor  61  and the electromagnet section  40  to both start the motor  61  and bring the electromagnet section  40  to an energized state. When receiving a control signal that turns off the pump  1 , the switch  52  operates so as to interrupt the electric power supplied from the power source  51  to the motor  61  and the electromagnet section  40  to both stop the motor  61  and bring the electromagnet section  40  to a non-energized state. 
         [0035]      FIG. 2  illustrates an exemplary cross section of the pump.  FIG. 2  may be a cross-sectional view of the pump  1  taken along the line A-A illustrated in  FIG. 1 . The impeller  20  includes a cylindrical bearing  22  having a through hole  21  through which the rotating shaft  32  passes formed in its rotation center portion and a plurality of vanes  23  extending radially from the outer circumferential side of the bearing  22 . Thus, when the impeller  20  rotates about the bearing  22 , the vanes  23  extrude fluid filling the inside of the pump casing  30  from upstream to downstream, thereby causing the fluid to flow. 
         [0036]      FIG. 3  illustrates an exemplary impeller. In  FIG. 3 , the impeller  20  is provided with the permanent magnet  24 . The impeller  20  includes the permanent magnet  24  being annular and surrounding the periphery of the through hole  21  at the end adjacent to the electromagnet section  40  illustrated in  FIG. 1 , for example. The permanent magnet  24  includes an end that is adjacent to the electromagnet section  40  and that forms a magnetic pole of either the north pole or the south pole and another end that is remote from the electromagnet section  40  and that forms a magnetic pole of the pole opposite to that of the end adjacent to the electromagnet section  40 . For example, the impeller  20  may include a magnetic element made of a material having small residual magnetism, such as iron, instead of the permanent magnet  24 . 
         [0037]      FIG. 4  illustrates an exemplary part of a pump. For example,  FIG. 4  illustrates an enlarged view of a part of the pump  1  indicated by the character B in  FIG. 1 .  FIG. 5  illustrates an exemplary of a pump. For example,  FIG. 5  illustrates a cross-sectional view of the part of the pump  1  taken along the line C-C illustrated in  FIG. 1 . The electromagnet section  40  is fixed to a drive shaft  62  for the motor  61  and rotates together with the drive shaft  62  for the motor  61 . The electromagnet section  40  includes a magnetic element  41 , a coil  42 , a cover  43 , electrode receiving grooves  44 (+) and  44 (−), and conductive rings  45 (+) and  45 (−). The magnetic element  41  may be a disc-shaped magnetic element and is attached to the drive shaft  62  for the motor  61 . The coil  42  is wound around the magnetic element  41  so as to circle around the outer circumferential side of the magnetic element  41 . The cover  43  may be a disc-shaped cover in which the magnetic element  41  and the coil  42  are housed. The electrode receiving grooves  44 (+) and  44 (−) are grooves that circle in parallel with each other in the outer circumferential side. The conductive rings  45 (+) and  45 (−) are conductive rings fit in the electrode receiving grooves  44 (+) and  44 (−), respectively. 
         [0038]      FIG. 6  illustrates an exemplary part of a pump. For example,  FIG. 6  illustrates the electrical connection between the electromagnet section  40  and the motor circuit  50 . One end of the coil  42  is electrically coupled to the conductive ring  45 (+), and another end of the coil  42  is electrically coupled to the conductive ring  45 (−). The conductive ring  45 (+) is in contact with an electromagnetic electrode (also called brush)  47 (+) attached to the motor casing  60 . The conductive ring  45 (−) is also in contact with an electromagnetic electrode  47 (−) attached to the motor casing  60 , similarly to the conductive ring  45 (+). The electromagnetic electrode  47 (+) is pressed against the conductive ring  45 (+) by a spring  46 (+). The electromagnetic electrode  47 (−) is also pressed against the conductive ring  45 (−) by a spring  46 (−). The electromagnetic electrodes  47 (+) and  47 (−) are coupled to the motor circuit  50 . Thus, when electricity is supplied from the motor circuit  50 , the electricity flows in the coil  42  through the electromagnetic electrodes  47 (+) and  47 (−) and the conductive rings  45 (+) and  45 (−). 
         [0039]      FIG. 7  illustrates an exemplary positional relationship in a part of a pump. For example,  FIG. 7  illustrates the positional relationship among the electromagnet section  40 , motor  61 , and impeller  20 . When the motor  61  rotates, the electromagnet section  40  fixed to the drive shaft  62  for the motor  61  rotates. When the electromagnet section  40  rotates, the conductive ring  45 (+) rotates in a state where the conductive ring  45 (+) is in electrical contact with the electromagnetic electrode  47 (+) and the conductive ring  45 (−) rotates in a state where the conductive ring  45 (−) is in electrical contact with the electromagnetic electrode  47 (−). Thus, even when the motor  61  is in a rotating state, electricity may be fed from the motor circuit  50  to the coil  42 , and the coil  42  may be energized. 
         [0040]    When the motor  61  rotates in a state where the coil  42  is energized, an eddy current occurs in the permanent magnet  24  receiving the magnetism of the coil  42 . Thus, the impeller  20  is driven by interaction between the eddy current occurring in the permanent magnet  24  and a magnetic field produced by the coil  42 . 
         [0041]    The orientation of the coil  42 , the direction of the electrical current passing through the coil  42 , or the orientation of the permanent magnet  24  in the electromagnet section  40  is adjusted such that the magnetic pole of the end of the electromagnet section  40  adjacent to the impeller  20  has the polarity opposite to the magnetic pole of the end of the permanent magnet  24  adjacent to the electromagnet section  40 . When the electromagnet section  40  is brought to an energized state by the passage of an electric current in the electromagnet section  40 , the impeller  20 , which includes the permanent magnet  24 , moves along the rotating shaft  32  and is attracted to the electromagnet section  40 . If the impeller  20  includes a magnetic element made of a material having small residual magnetism, such as iron, the polarity of the magnetic pole of the end of the electromagnet section  40  adjacent to the impeller  20  may be either the north pole or the south pole. 
         [0042]      FIG. 8  illustrates an exemplary internal structure of a pump. For example,  FIG. 8  may illustrate the internal structure of the pump  1  when the impeller  20  is attracted to the electromagnet section  40 . When the electromagnet section  40  is brought to an energized state, the impeller  20  is attracted to the electromagnet section  40 , as illustrated in  FIG. 8 . When the electromagnet section  40  is brought to a non-energized state, the magnetism of attracting the impeller  20  to the electromagnet section  40  is reduced, and the impeller  20  is moved to the housing section  31  by its own weight, as illustrated in  FIG. 1 . For example, the impeller  20  is positioned inside the pump chamber channel  33  or housed in the housing section  31  in the pump  1  under the control on an electrical current passing through the coil  42  of the electromagnet section  40 . 
         [0043]    Because the impeller  20  is positioned inside the pump chamber channel  33  or housed in the housing section  31 , situations where the stopped impeller  20  becomes an obstacle to the channel may be reduced. 
         [0044]    The switch  52  illustrated in  FIG. 1  becomes an “open” state based on a control signal indicating “stop,” and the feeding of electricity to the motor  61  and electromagnet section  40  is interrupted. The impeller  20  comes to a stop, is housed in the housing section  31 , as illustrated in  FIG. 1 , and may fail to become an obstacle to the channel.  FIG. 9  illustrates an exemplary part of a pump.  FIG. 9  illustrates a cross-sectional view of the part of the pump  1  taken along the line D-D illustrated in  FIG. 1 . In a state where the pump  1  does not run, when the impeller  20  is housed in the housing section  31 , the impeller  20  is absent from the pump chamber channel  33 . Thus, the impeller  20  may fail to become the obstacle to fluid moving into the pump casing  30  of the pump  1 , passing through the pump chamber channel  33 , and moving out of the pump casing  30 , whereby the channel may be ensured. 
         [0045]    The number of magnetic poles of the end of the electromagnet section  40  adjacent to the permanent magnet  24  and the number of magnetic poles of the end of the permanent magnet  24  adjacent to the electromagnet section  40  may be one or more than one. Power may be transmitted by the use of attraction and repulsion of the magnet. 
         [0046]    The impeller  20  may be moved to the housing section  31  by its own weight. For example, the impeller  20  may be moved to the housing section  31  by the use of repulsion of an elastic body, such as a spring or sponge, when the electromagnet section  40  is in a non-energized state. When repulsion of an elastic body is used, the housing section  31  may be positioned below, at the side of, or above the pump chamber channel  33 . The electromagnet section  40  may obtain power directly from the drive shaft  62  for the motor casing  60  or, for example, may indirectly obtain power through a power transmitting unit, such as a transmission mechanism. 
         [0047]    The degree of flexibility in the pump mounting direction in the above-described configuration may be increased. For example, the pump illustrated in  FIG. 1  may be mounted such that the top in the drawing is oriented downward. 
         [0048]    The electromagnet section  40  may be electrically coupled to the motor circuit  50  through the conductive rings  45 (+) and  45 (−) disposed on the outer circumferential side of the cover  43 . The electromagnet section  40  may be electrically coupled to the motor circuit  50  through a conductive ring disposed in the vicinity of the drive shaft  62 , for example. Power may be fed to the electromagnet section  40  through electric wire coupled to a rotor coil of the motor  61 . 
         [0049]    The electrical connection between the electromagnet section  40  and the motor circuit  50  may have a configuration in which a coil spring and a brush are combined. The electrical connection between the electromagnet section  40  and the motor circuit  50  may include a leaf spring or may have a configuration in which a brush itself is a leaf spring, for example. 
         [0050]    The motor casing  60  and the pump casing  30  in the pump  1  may be separate components to facilitate replacement of the motor  61 . The pump casing  30  and the motor casing  60  may be integrated. 
         [0051]    The pump casing  30  may be formed from a cylindrical component. The pump casing  30  may have a cubic shape, a conical shape, or other shapes where the housing section  31  and the pump chamber channel  33  may be formed therein. 
         [0052]    The opposite ends of the rotating shaft  32  may be fixed to the bottom of the housing section  31  and the top of the pump chamber channel  33 , respectively. One end of the rotating shaft  32  may be fixed to the bottom of the housing section  31  or the top of the pump chamber channel  33 , for example. 
         [0053]    The impeller  20  may be rotatably supported by the rotating shaft  32 . The impeller  20  may be supported by being in contact with the inner circumferential wall of the pump casing  30  having a cylindrical shape, instead of by the rotating shaft  32 , for example. The impeller  20  may be supported inside the pump casing  30  by magnetic force, for example. 
         [0054]    The impeller  20  may be moved to the housing section  31  by inversion of the polarity of each of the magnetic poles of the electromagnet section  40 .  FIG. 10  illustrates an exemplary motor circuit. A motor circuit  150  illustrated in  FIG. 10  inverts the polarity of the magnetic pole of the electromagnet section  40 . 
         [0055]    The motor circuit  150  includes a power source  151 , a switch  152 , and a polarity inverter  153 , similarly to the motor circuit  50  illustrated in  FIG. 1 . 
         [0056]    The switch  152  controls electric power supplied from the power source  151  to the motor  61  based on a control signal input from the outside. For example, when a control signal that turns on the pump  1  is input to the switch  152 , electric power is supplied from the power source  151  to the motor  61 , and the motor  61  starts. When a control signal that turns off the pump  1  is input to the switch  152 , electric power supplied from the power source  151  to the motor  61  is interrupted, and the motor  61  comes to a stop. 
         [0057]    The polarity inverter  153  inverts the polarity of electricity to be sent from the power source  151  to the electromagnet section  40 . For example, when a control signal that turns on the pump  1  is input to the polarity inverter  153 , the polarity inverter  153  energizes the electromagnet section  40  such that the polarity of the magnetic pole of the end of the electromagnet section  40  adjacent to the permanent magnet  24  is opposite to the polarity of the magnetic pole of the end of the permanent magnet  24  adjacent to the electromagnet section  40 . When a control signal that turns off the pump  1  is input to the polarity inverter  153 , the polarity inverter  153  energizes the electromagnet section  40  such that the polarity of the magnetic pole of the end of the electromagnet section  40  adjacent to the permanent magnet  24  becomes the same as the polarity of the magnetic pole of the end of the permanent magnet  24  adjacent to the electromagnet section  40 . 
         [0058]    For example, when the pump  1  illustrated in  FIG. 1  is coupled to the motor circuit  150  illustrated in  FIG. 10 , in the case where a control signal that turns on the pump is input, the impeller  20  is attracted to the electromagnet section  40  by attraction of magnetism. In the case where a control signal that turns off the pump is input, the impeller  20  is forced away from the electromagnet section  40  by repulsion of magnetism. 
         [0059]    Thus, the impeller  20  in the case where the motor circuit  150  illustrated in  FIG. 10  is used in the pump  1  illustrated in  FIG. 1  may be housed in the housing section  31  more quickly than that in the case where the motor circuit  50  illustrated in  FIG. 1  is used. 
         [0060]    The degree of flexibility in the pump mounting direction in the above-described configuration may be increased. For example, the pump illustrated in  FIG. 1  may be mounted such that the top in the drawing is oriented downward. When the motor circuit  150  illustrated in  FIG. 10  is used, an electromagnet section for moving the impeller  20  may be provided separately from the electromagnet section  40  for transmitting rotational power from the motor  61  to the impeller  20 . 
         [0061]    A switch that interrupts an electrical current to the electromagnet section  40  after the elapse of a set period of time from the receipt of a control signal that turns off the pump  1  may be added to the motor circuit  150  illustrated in  FIG. 10 . By the addition of the switch interrupting the electrical current to the electromagnet section  40 , the electrical current flowing in the electromagnet section  40  may be interrupted during stoppage of the pump  1 . When the electrical current flowing in the electromagnet section  40  is interrupted after the impeller  20  is housed in the housing section  31 , the impeller  20  remains in the housing section  31  by its own weight. 
         [0062]    Because the impeller  20  is moved to the housing section  31  in the above-described configuration more quickly than that in the pump  1  illustrated in  FIG. 1 , the time for which the stopped impeller  20  is an obstacle to the channel may be reduced. 
         [0063]      FIG. 11  illustrates an exemplary communication apparatus. A unit  102  including an electronic component  101  being one example of heat-generating equipment is mounted in a communication apparatus  100  illustrated in  FIG. 11 . The communication apparatus  100  transmits and receives various kinds of data and may have redundancy from the aspect as a social infrastructure. Thus, a cooling system that cools the electronic component  101  may have redundancy. 
         [0064]      FIG. 12  illustrates an exemplary cooling system. For example, a cooling system  106  illustrated in  FIG. 12  includes pumps  1 A and  1 B corresponding to the pump  1  illustrated in  FIG. 1 , a heat exchanger  103 , a circulation channel  104 , and a control device  105 . The control device  105  sends a control signal to the motor circuit  50  included in each of the pumps  1 A and  1 B. The cooling system  106  removes heat from the electronic component  101  disposed along the circulation channel  104  by the use of a cooling medium, one kind of fluid, and dissipates the heat to the outside of the system. The pumps  1 A and  1 B may be disposed in series on the circulation channel  104 . The cooling medium circulates through the circulation channel  104  when at least one of the pumps  1 A and  1 B is in a running state. 
         [0065]    The cooling medium may be either liquid or gas that may be the fluid; liquid may efficiently cool the heat-generating equipment. Only one pump  1  illustrated in  FIG. 1 , or alternatively, a plurality of, for example, three or more pumps  1  may be disposed on the circulation channel  104  in the cooling system  106 . 
         [0066]      FIG. 13  illustrates an exemplary control process. The control device  105  illustrated in  FIG. 12  may perform the control process illustrated in  FIG. 13 . 
         [0067]    (In operation S 101 ) When the communication apparatus  100  is activated, the control device  105  activates either one of the pumps  1 A and  1 B (hereinafter referred to as the first pump). The electromagnet section  40  in the activated first pump is brought to an energized state, and the impeller  20  moves from the housing section  31  to the pump chamber channel  33 . The impeller  20  having moved to the pump chamber channel  33  is driven inside the pump chamber channel  33  by power transmitted from the electromagnet section  40  rotated by the motor  61  through magnetism. 
         [0068]    (In operation S 102 ) The control device  105  monitors the presence or absence of an anomaly of the first pump. The presence or absence of an anomaly of the pump may be determined based on various parameters representing the statuses of the pump. Examples of the parameters representing the statuses of the pump may include the amount of flow of the cooling medium flowing through the circulation channel  104 , the electrical current of the motor  61 , the number of revolutions of the motor  61  or impeller  20 , and the electrical current value of the electromagnet section  40 . 
         [0069]    (In operation S 103 ) When detecting an anomaly of the first pump, the control device  105  stops the first pump. The electromagnet section  40  in the stopped first pump is brought to a non-energized state, and the impeller  20  moves from the pump chamber channel  33  to the housing section  31 . Thus, the channel coupling the inlet and outlet of the first pump and allowing the cooling medium to flow therethrough inside the pump casing  30  is ensured. For example, obstruction to circulation of the cooling medium by the impeller  20  of the first pump may be reduced. The impeller  20  having moved to the housing section  31  loses power transmitted from the electromagnet section  40  through magnetism and comes to a stop. 
         [0070]    (In operation S 104 ) After stopping first pump, the control device  105  activates the other pump having stopped so far out of the pumps  1 A and  1 B (hereinafter referred to as the second pump). The impeller  20  in the activated second pump moves to the inside of the pump chamber channel  33  and is driven inside the pump chamber channel  33 . The stopping of the first pump ensures the channel coupling the inlet and outlet of the first pump and allowing the cooling medium to flow therethrough inside the pump casing  30 . Thus, the activation of the second pump enables the cooling medium to normally circulate in the circulation channel  104 . 
         [0071]    When the control device  105  performs the control process illustrated in  FIG. 13 , one stopped pump out of the pumps  1 A and  1 B may be used as a reserve pump. Thus, when a plurality of pumps are disposed in series, a path for bypassing the pumps is not provided, and redundancy of the cooling system  106  may be achieved. 
         [0072]    The impeller  20  included in each of the pumps  1 A and  1 B is driven by power transmitted through magnetism. For example, the pumps  1 A and  1 B may not include a power transmission shaft or a shaft seal for use in the pump. Thus, the pump casing  30  and the motor casing  60  in the pump  1  may be formed such that they may be separated. For example, if an anomaly based on the motor  61  in the first pump occurs in the first pump, the motor  61  in the first pump may be replaced or repaired without stopping of the second pump. 
         [0073]      FIG. 14  illustrates an exemplary replacement of a motor. In  FIG. 14 , the motor  61  in the first pump may be replaced. If the motor  61  in the first pump has broken down, this faulty motor  61  is detached together with the motor casing  60 , and a normal motor  61  is attached. The pump casing  30  is sealed except for the connections with the pipes attached to the outer circumferential surface of the pump casing  30 . Thus, if the motor  61  or the motor casing  60  is detached from the pump casing  30 , leakage of the cooling medium flowing inside the pump casing  30  is reduced. The pump  1 A is repaired in a state where the pump  1 B runs. 
         [0074]    Examples of the cause of a breakdown of the pump include a breakdown of an electric component, such as a motor, and abrasion of a bearing or a shaft seal section of the motor. The impeller  20  in the pump  1  illustrated in  FIG. 1  is driven by power transmitted through magnetism from the electromagnet section  40 , thus making the fluid flow. Because the pump  1  illustrated in  FIG. 1  includes no shaft seal section, breakdowns may be reduced. In the case where a breakdown occurs in a component inside the pump casing  30 , if the impeller  20  is housed in the housing section  31 , another pump continues running while the faulty pump is set aside, the cooling system  106  may maintain its cooling function. 
         [0075]      FIG. 15  illustrates an exemplary control process. The control device  105  illustrated in  FIG. 12  may perform the control process illustrated in  FIG. 15 . 
         [0076]    (In operation S 201 ) When the communication apparatus  100  is activated, the control device  105  illustrated in  FIG. 12  monitors the temperature of the electronic component  101 . The temperature of the electronic component  101  may be obtained from a signal of a temperature sensor (not illustrated) disposed in the vicinity of the electronic component  101  or from temperature data output from the electronic component  101 . The pumps  1 A and  1 B in the cooling system illustrated in  FIG. 12  may fail to become an obstacle to the circulation channel  104  in a state where the pumps  1 A and  1 B are stopped. Thus, when the circulation channel  104  expects a natural flow of the cooling medium, hindrance to the natural flow is reduced. 
         [0077]    (In operation S 202 ) When the temperature of the electronic component  101  reaches a value preset as the temperature at which the first pump is activated, the control device  105  activates the first pump. 
         [0078]    (In operation S 203 ) After activating the first pump, the control device  105  monitors the temperature of the electronic component  101 . 
         [0079]    (In operation S 204 ) When the temperature of the electronic component  101  reaches a value preset as the temperature at which the second pump is activated, the control device  105  activates the second pump. 
         [0080]    (In operation S 205 ) When the temperature of the electronic component  101  is below the value preset as the temperature at which the first pump is activated, the control device  105  stops the first pump. 
         [0081]    (In operation S 206 ) When the temperature of the electronic component  101  is below the value preset as the temperature at which the second pump is activated, the control device  105  stops the second pump. 
         [0082]    When detecting an anomaly of the pump in a repetition of operations S 201  to S 206 , the control device  105  performs a subroutine. 
         [0083]      FIG. 16  illustrates an exemplary processing of the control device. The processing illustrated in  FIG. 16  may be a subroutine performed by the control device illustrated in  FIG. 12 . 
         [0084]    (In operation S 301 ) When detecting an anomaly of the pump in a repetition of operations S 201  to S 206 , the control device  105  determines the presence or absence of a reserve pump. For example, when both the pumps  1 A and  1 B are running or when a stopped pump out of the pumps  1 A and  1 B is faulty, the control device  105  determines that there is no reserve pump. 
         [0085]    (In operation S 302 ) When determining that there is a reserve pump in operation S 301 , the control device  105  stops the first pump. 
         [0086]    (In operation S 303 ) After stopping the first pump, for example, the pump in which an anomaly has been detected, the control device  105  activates the second pump, for example, the pump as the reserve pump. 
         [0087]    (In operation S 304 ) When determining that there is no reserve pump in operation S 301 , the control device  105  stops the unit  102  to be cooled by in the cooling system  106 . 
         [0088]    For example, power supplied to the unit  102  is interrupted to protect the electronic component  101  against a breakdown based on an increase in temperature. 
         [0089]    When the control device  105  performs the control process illustrated in  FIG. 15 , an appropriate number of pumps may be run in accordance with the temperature of the electronic component  101 , and one stopped pump out of the pumps  1 A and  1 B may be used as a reserve pump. Thus, power consumption of the pumps may be reduced, and redundancy of the cooling system  106  may be achieved. 
         [0090]      FIG. 17  illustrates an exemplary transport system. A transport system  200  illustrated in  FIG. 17  transports liquid inside a tank. The pump  1  illustrated in  FIG. 1  may be used in a circulation channel through which fluid circulates. The pump  1  illustrated in  FIG. 1  may be used in a channel through which fluid does not circulate. 
         [0091]    For example, the pump  1  illustrated in  FIG. 1  may be used in the transport system  200  in which tanks  201 A and  201 B are coupled to each other with a pipe  202 , as illustrated in  FIG. 17 . When the pump  1  illustrated in  FIG. 1  is disposed on the pipe  202  in the transport system  200 , even if the pump  1  is broken down, liquid may be transported employing a height difference or a pressure difference between the tanks  201 A and  201 B. 
         [0092]    Even if the pump  1  comes to a stop, the impeller  20  may fail to become an obstruction to the channel for fluid. 
         [0093]    A plurality of pumps  1 , at least one of which is illustrated in  FIG. 1 , may be disposed on the pipe  202  in the transport system  200 . The control device for controlling each of the pumps  1  may perform the processes illustrated in  FIGS. 13 ,  15 , and  16 . 
         [0094]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.