Patent Publication Number: US-2018043321-A1

Title: Mixing unit and method for stirring fluid

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part application which claims priority from PCT Application No. PCT/JP2017/008011, titled “Stirring Unit, Stirring Device, Stirring Method, Cell Culture Method, Reaction Promoting Method, and Method of Assembling Stirring Unit”, filed on Feb. 28, 2017; which claims priority the benefit of Japanese Patent Application No. 2016-082808, titled “Stirring Unit, Stirring Device, and Stirring Method”, filed on Apr. 18, 2016, the contents of which are incorporated in this disclosure by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
       1 . Field of the Invention 
     The present invention relates to a mixing unit and a method for stirring a fluid, and, more particularly, relates to a stirring unit, a stirring device, a stirring method, a cell cultivation method, a reaction promoting method, and a method of assembling a stirring unit for stirring a fluid contained in a vessel. 
       2 . Description of the Related Art 
     Conventionally, in order to stir a fluid contained in a vessel, there is well known a combination of a magnetic stirrer and a stirring unit. The stirring unit is placed so as to be submerged in a bottom part of the vessel, and rotates by receiving a rotational magnetic force from the magnetic stirrer to stir the fluid in the vessel. As the conventional stirring unit, there is a rotating body which is a stirring bar or a disk having a cross-shaped protrusion with magnets at ends of the disk, or a structure having a stirring blade provided on a rotating body. 
     However, in a conventional stirring unit, in order to stir a fluid in a vessel, there is a problem that it is difficult to stir the fluid located in upper portion of the vessel above an upper part of a center of the stirring unit having a small tangential speed. This is because, the fluid at an outer peripheral portion of the vessel is easy to be stirred by a large force of rotation transmitted from end portions of the stirring unit causing large turbulence of the flow of the fluid, while the fluid at an upper central portion of the vessel is difficult to be stirred by a small force of rotation transmitted from the central portion of the stirring unit causing small turbulence of the flow of the fluid. In addition, in the vertical direction within the vessel, the force transmitted from the stirring unit is larger toward the bottom side closer to the stirring unit but smaller toward the upper side due to viscosity of the fluid. As a result, the fluid in the vessel is stirred most quickly at the outer peripheral portion of the bottom of the vessel, and the fluid in an upper central portion of the vessel is stirred most slowly. As described above, with the conventional stirring unit, stirring of the fluid in the vessel proceeds from the outer peripheral portion of the vessel to the central portion of the vessel and also proceeds from the vessel bottom to the upper portion of the vessel. Therefore, it takes a relatively long time for uniformly stirring the entire fluid in the vessel. 
     SUMMARY OF THE INVENTION 
     One or more embodiments of the present invention provides a mixing unit and a method for stirring a fluid, and, more particularly, a stirring unit, a stirring device, a stirring method capable of efficiently and rapidly stirring a fluid in a vessel, a cell cultivation method using the stirring unit, a reaction promoting method, and a method of assembling the stirring unit. 
     According to one or more embodiments of the present invention, there is provided a stirring unit for stirring a fluid contained in a vessel including a mixing body for stirring the fluid by rotating around a rotation axis, and a magnet or a magnetic substance for receiving a rotating magnetic field for rotating the mixing body, wherein a suction port and a discharge port for the fluid are provided on a surface of the mixing body, one or two or more holes connecting the suction port and the discharge port are provided within the mixing body, the suction port is disposed at a position on the rotation axis or at a position closer to the rotation axis than the discharge port, and the discharge port is disposed at a position outside the rotation axis than the suction port. 
     According to the above configuration, as the stirring unit disposed in the vessel is rotated, the fluid within the mixing body is caused to flow out from the discharge port to the outside by a force generated from rotation. Then, the fluid in the vicinity of the central upper portion in the vessel is sucked into the mixing body from the suction port of the mixing body. As a result, the fluid in the outer peripheral portion of the stirring unit is mixed by being disturbed by the fluid flowing out from the discharge port. As described above, it is possible to suck the fluid at the center upper part in the vessel from the suction port of the mixing body without retention and allow the fluid to flow out from the discharge port, so that the fluid can be efficiently stirred and the time for uniformly mixing the entire fluid in the vessel can be shortened. 
     According to one or more embodiments of the present invention, there is provided a stirring device including the stirring unit and a rotating magnetic field generating unit for generating a rotating magnetic field for rotating the stirring unit. 
     According to one or more embodiments of the present invention, there is provided a stirring method including; disposing a stirring unit at a bottom of a vessel; rotating the stirring unit at the bottom within the vessel containing the fluid; sucking the fluid at a central upper portion in the vessel from a suction port by the stirring unit; passing the fluid within the stirring unit; and flowing out the fluid from the discharge port of the stirring unit to an outer peripheral portion within the vessel to stir the fluid. 
     According to one or more embodiments of the present invention, there is provided a cell cultivation method in which a fluid in a vessel is used as a cell cultivation medium and the cell cultivation solution is stirred with the stirring unit, or a reaction promoting method in which a fluid in the vessel is used as a reaction solution and the reaction solution is stirred with the stirring unit thereby promoting the reaction. 
     According to one or more embodiments of the present invention, there is provided a method for assembling a stirring unit including a step of forming a mixing body and a step of fixing the mixing body to a base having a magnet or a magnetic substance, wherein the step of forming the mixing body includes a step of aligning and stacking a plurality of mixing elements to form the mixing body, and the step of fixing the mixing body to the base has a step of fixing the mixing body to the base by penetrating the mixing body in the stacking direction by a fixing member. 
     Thus, according to the present invention, since a large fluid flow occurs in the vertical direction of the vessel, the fluid in the vessel can be rapidly mixed. Therefore, it is possible to shorten the mixing time of the fluid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view showing a stirring device using a stirring unit according to a first embodiment of the present invention; 
         FIG. 2A  is a perspective view of the stirring unit of  FIG. 1 , and  FIG. 2B  is a side view of the stirring unit of  FIG. 2A ; 
         FIGS. 3A and 3B  are a perspective view and a side view of a base employed in the stirring unit of  FIG. 2A , and  FIG. 3C  is a side view of a modification of the base of  FIG. 3B ; 
         FIG. 4  is a plan view showing a configuration of mixing elements constituting a mixing body of the stirring unit shown in  FIG. 2A ; 
         FIGS. 5A and 5B  are a partial plan view and a side sectional view of the mixing body showing a fluid flow state within the same; 
         FIG. 6  is a plan view showing a configuration of mixing elements according to a modification  1  of the mixing body; 
         FIG. 7A  is a perspective view of mixing elements according to a modification  2  of the mixing body, and  FIG. 7B  is a partial side sectional view of the mixing elements of  FIG. 7A  showing a fluid flow state within the same; 
         FIG. 8A  is a perspective view of mixing elements according to a modification  3  of the mixing body, and  FIG. 8B  is a partial cross-sectional view showing a sectional shape of the mixing elements; 
         FIGS. 9A and 9B  are side sectional views of the respective mixing bodies according to a modification  4  of the mixing body; 
         FIGS. 10A, 10B and 10C  are perspective views of the respective bases according to modifications of the base in the first embodiment; 
         FIGS. 11A and 11B  are a perspective view and a side view of a base of another example according to a modification of the base of the first embodiment; 
         FIG. 12  is a perspective view of a stirring unit according to a second embodiment of the present invention; 
         FIGS. 13A, 13B, and 13C  are perspective views showing other examples of the stirring unit of the second embodiment; 
         FIGS. 14A, 14B, and 14C  are perspective views of stirring units according to a third embodiment of the present invention; 
         FIGS. 15A and 15B  are perspective views showing other examples of the stirring unit of the third embodiment; 
         FIGS. 16A, 16B, and 16C  are perspective views of stirring units according to a fourth embodiment of the present invention; 
         FIG. 17  is a perspective view showing an example of a stirring unit according to a fifth embodiment of the present invention; 
         FIGS. 18A, 18B, 18C, 18D, 18E, and 18F  are perspective or plain views of various stirring units according to the fifth embodiment of the present invention; 
         FIG. 19A  is perspective view of a stirring unit according to a sixth embodiment of the present invention, FIG 19 B is a perspective view of a base modified from a base employed in the stirring unit of  FIG. 19A , and  FIG. 19C  is a perspective view of another modified base from  FIG. 19A ; 
         FIGS. 20A and 20B  are a perspective view and a cross-sectional view of still another modified base from  FIG 19A ; 
         FIG. 21  is a perspective view of a stirring unit according to a seventh embodiment of the present invention; 
         FIGS. 22A and 22B  are photographs showing stirring units used in examples of the present invention, and  FIGS. 22C and 22D  are photographs showing stirring units used as comparative examples; 
         FIGS. 23A and 23B  are photographs illustrating a state of stirring in the examples of  FIGS. 22A and 22B ; and 
         FIGS. 24A and 24B  are photographs illustrating a state of stirring in the comparative examples of  FIGS. 22C and 22D . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention will be described below with reference to the accompanying drawings. In embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention. 
       FIG. 1  is a cross-sectional view of a stirring device according to a first embodiment of the present invention, which includes a stirring unit  1  and a magnetic stirrer  4  for generating a rotating magnetic field for rotating stirring unit  1 . 
     Stirring unit  1  is disposed in a vessel  6  such as a beaker, and rotated by receiving a rotating magnetic field from magnetic stirrer  4  on which vessel  6  is placed to stir a fluid A such as a sample contained in vessel  6 . It should be noted that the present invention is not limited to the case where stirring unit  1  is disposed in vessel  6  such as the beaker and used for experiments and the like, but may be arranged in vessel  6  such as a tank for containing fluid A such as various raw materials including being used for commercial use.  FIG. 2A  is a perspective view of stirring unit  1  shown in  FIG. 1 , and  FIG. 2B  is a side view of stirring unit  1  of  FIG. 2A . Stirring unit  1  includes a mixing body  2  for stirring fluid A by rotating about a rotation axis S, and a base  3  incorporating magnets  5   a  and  5   b  for supporting mixing body  2  and receiving a rotating magnetic field. Although permanent magnets are used for magnets  5   a  and  5   b,  magnetic bodies may be used instead of them (this also applies to embodiments other than this embodiment). 
       FIG. 3  A and  FIG. 3  B respectively show a perspective view and a side view of base  3  which is provided with a pillar-shaped bar body  31  that is horizontally placed. At both ends of an upper surface of bar body  31 , there are provided screw cylinder portions  33  for mounting and fixing mixing body  2 , respectively. At both ends of bar body  31 , there are also respectively accommodated magnets  5   a  and  5   b  which receive the rotating magnetic field from magnetic stirrer  4  of  FIG. 1 . The respective magnets  5   a  and  5   b  are arranged so that the magnetization direction faces the vertical direction orthogonal to the longitudinal direction of bar body  31  and also the positions of the magnetic poles of magnets  5   a  and  5   b  are opposite to each other as shown in  FIG. 1 . In the horizontally placed state of bar body  31  as shown in  FIG. 3A , for example, when the N pole of one magnet  5   a  is disposed on its lower surface side, the S pole of other magnet  5   b  is disposed on its lower surface side. Ring, cylindrical or rectangular magnets may be used as magnets  5   a  and  5   b  but a bar magnet having such a size as to be housed over the longitudinal direction of bar body  31  may be housed within bar body  31 . 
     In addition, bar body  31  is provided with an annular portion  32  for preventing stirring unit  1  from falling. Annular portion  32  is connected to both end portions of bar body  31  so as to be flush with a lower surface of bar body  31 . An arcuate support protrusion  34  to be in contact with a bottom surface of vessel  6  is protruded at a center of the lower surface of bar body  31 . As a result, since support protrusion  34  serves as a center of rotation, stirring unit  1  is supported almost without shifting during rotation. Therefore, the frictional resistance between stirring unit  1  and the bottom surface of vessel  6  becomes extremely small, so that stirring unit  1  can be rotated smoothly. 
     If desired, two or more arc-shaped stabilizing protrusions may be provided at equal intervals with a height equal to or less than the protrusion height of support protrusion  34  on the lower surface of annular portion  32  (including the connected portion of bar body  31 ). In this case, even if the attitude of stirring unit  1  supported by support protrusion  34  at the time of rotation is inclined obliquely due to the weight of mixing body  2  or the like, the stabilizing protrusions contact the bottom surface of vessel  6  to keep it in a stable attitude.  FIG. 3  C shows a side view of a base  3  as a modification of  FIG. 3B , in which support protrusion  34  may be formed over the entire lower surface of bar body  31 . 
     As shown in  FIG. 2A  and  FIG. 2B , mixing body  2  is constituted by a stacked structure in which a plurality of mixing elements  21  (here,  10  elements) having a disk or substantially disk shape are stacked, and the stacked mixing elements  21  are fastened to screw cylinder portions  33  of base  3  (see  FIG. 3A ) to be fixed to base  3  by inserting bolts  11  (fixing members) through bolt holes “h 1 ” (see  FIG. 4 ) provided at two locations at 180 degree apart in an outer peripheral portion of the elements. Thus, mixing body  2  in which the plurality of mixing elements  21  are stacked and disassemblably integrated is easily constructed and fixed to base  3 . Further, by constituting the plurality of mixing elements  21  that can be disassembled into each element, it is possible to easily carry out a cleaning operation such as removal of residues and foreign matters remaining in each disassembled mixing element  21  (first through holes  22 , second through holes  23  and the like shown in  FIG. 4 ). The structure for integrating the plurality of mixing elements  21  and the structure for attaching mixing body  2  to base  3  are not limited to fixing with bolts  11  but also may be a disengageable attachment structure such as a concave and convex fitting structure. 
     As shown in  FIG. 4 , mixing body  2  is formed by alternately stacking two kinds of mixing elements  21   a  and  21   b,  and these two kinds of mixing elements  21   a  and  21   b  each have a plurality of first through holes  22  penetrating in the thickness direction. Mixing elements  21   a  and  21   b  shown in  FIG. 2  have different numbers of partition walls in the circumferential direction and the radial direction from those shown in  FIG. 4 , but the other structures are common. The plurality of first through holes  22  are provided along surfaces extending in the extending direction of the disk-shaped mixing elements  21   a  and  21   b.  Each of mixing elements  21   a  and  21   b  at its central portion is provided with a second through hole  23  having an opening area larger than that of first through hole  22 . Second through hole  23  is formed in a substantially circular shape. As shown in  FIGS. 2A and 2B , a cylindrical hollow portion  24  in which second through holes  23  communicate with each other is formed by stacking mixing elements  21   a  and  21   b.  Upper and lower openings of hollow portion  24  constitute a suction ports  20 α of fluid A. The central axis of hollow portion  24  coincides with rotation axis S of stirring unit  1 . Therefore, suction ports  20 α are arranged at a position on rotation axis S. 
     Further, as shown in  FIG. 4 , first through holes  22  are formed in a substantially rectangular shape as seen in plan view, and arranged concentrically around the center point of second through hole  23 . First through holes  22  are arranged in a staggered manner, and each arrangement pattern itself of first through holes  22  is different in two kinds of mixing elements  21   a  and  21   b.  In mixing element  21   a,  first through holes  22  are closed on an inner peripheral surface facing second through hole  23  and open on an outer peripheral surface of element  21   a,  while in other mixing element  21   b  first through holes  22  are open on an inner peripheral surface facing second through hole  23  and closed on an outer peripheral surface of element  21   b.  As shown in  FIGS. 2A and 2B , first through holes  22  opened to the outer peripheral surfaces of mixing elements  21   a  constitute discharge ports  20 β of fluid A. Accordingly, discharge ports  20 β are disposed at positions outside the rotation axis S than suction ports  20 α which are the upper and lower end openings of hollow portion  24  (that is, at a position outside in the radial direction orthogonal to rotation axis S). 
     First through holes  22  are formed to be the same in size in the same circumferential directions of mixing elements  21   a  and  21   b,  and formed so as to become larger toward the outside of the mixing elements  21   a  and  21   b  in the radial directions. Further, in the overlapping state of the two types of mixing elements  21   a  and  21   b,  each area of a portion where first through holes  22  overlap with each other is uniform in the circumferential direction. 
     First through holes  22  of the adjacent mixing elements  21   a  and  21   b  in mixing body  2  are arranged so as to partially overlap with each other in the radial direction and the circumferential direction, and communicate with each other in the stacking direction and the extending direction of mixing elements  21   a  and  21   b.  In other words, the respective partition walls between first through holes  22  extending in the radial direction and in the circumferential direction of mixing elements  21   a  and  21   b  are disposed with mutually different positions between the adjacent mixing elements  21   a  and  21   b.  Accordingly, an inner portion of mixing body  2  is formed such that fluid A is sequentially passed between first through holes  22  of adjacent mixing elements  21  and  21   b  so that fluid A is divided in the stacking direction and the extending direction of mixing elements  21   a  and  21   b.  Thus, as shown in  FIG. 2A , the plurality of first through holes  22  within mixing body  2  form a plurality of “flow paths” for connecting an upper opening of hollow portion  24  serving as suction port  20 α and first through holes  22  opened to the outer circumferential surface of mixing element  21   a  serving as discharge port  20 β. As shown in  FIG. 2B , a lower opening of hollow portion  24  also serves as suction port  20 α connecting with discharge port  20 β through hollow portion  24  and first through holes  22 . 
     Mixing elements  21   a  and  21   b  and base  3  constituting mixing body  2  are made of a resin such as polyethylene, polypropylene, fluorine resin or the like, but may be made of ceramic, metal, or the like. By making mixing elements  21   a  and  21   b  and base  3  made of resin, it is possible to easily and inexpensively manufacture mixing elements  21   a  and  21   b  and base  3  by resin molding. Further, in the case where the mixing elements  21   a  and  21   b  and the base  3  are made of a resin other than the fluorine-based resin, the surface layer may be formed of a fluorine-based resin by coating or the like. In this case, the chemical resistance is improved and it can be preferably used also in the field of mixing chemical agents and the like. 
     As a method of assembling stirring unit  1  of  FIG. 2A , there are provided a step of forming mixing body  2  and a step of fixing mixing body  2  to base  3 . 
     In the step of forming mixing body  2 , a plurality of mixing elements  21   a  and  21   b  are aligned at predetermined positions in the circumferential direction and are alternately stacked to form mixing body  2  as shown in  FIG. 4 . In this case, since the bolt holes “h 1 ” to be inserted by bolts  11  (fixing member) are provided at a pair of outer peripheral portions of mixing elements  21   a  and  21   b,  the respective mixing elements  21   a  and  21   b  are stacked by inserting bolts  11  through bolt holes “h 1 ” of the outer peripheral portion, whereby the elements can be easily aligned at predetermined positions in the circumferential direction. In the case where bolt holes “h 1 ” of mixing elements  21   a  and  21   b  are located closer to the center or are provided at the center portion, the elements can be efficiently aligned at a predetermined position in the circumferential direction by bringing a jig or the like into contact with the outer peripheral portion. In the step of fixing mixing body  2  to base  3 , mixing body  2  stacked by the plurality of mixing elements  21   a  and  21   b  is penetrated by bolts  11  in the stacking direction, and fixed by screwing bolts  11  into screw holes “h” of the base  3 . Through the above steps, the plurality of mixing elements  21   a  and  21   b  are aligned in predetermined positions in the circumferential direction to form the stacked mixing body  2 , and the attachment to base  3  is completed, so that the assembly of stirring unit  1  is efficiently performed. 
     Meanwhile, as shown in  FIG. 1 , magnetic stirrer  4  includes a main body  41 , an upper surface of which is horizontal, and a rotating magnetic field generating section  42  arranged within main body  41 . Rotating magnetic field generating section  42  includes a plate-shaped driving rotator  43  extending in the horizontal direction and magnets  46   a  and  46   b  provided on both upper end portions of a driving rotator  43 , respectively. Each of magnets  46   a  and  46   b  is disposed such that the magnetization direction faces in a direction (vertical direction) perpendicular to the extending surface (horizontal plane) of driving rotator  43 , and the magnetic poles (N pole and S pole) are arranged so that their positions are opposite to each other. A motor  45  is connected to a central portion of a lower surface of driving rotator  43  via a shaft portion  44 . By rotation driving of motor  45 , driving rotator  43  and the pair of magnets  46   a  and  46   b  are rotated in the horizontal direction so that a rotating magnetic field is generated on an upper surface of main body  41 . 
     Next, a method of stirring fluid A using stirring unit  1  having the above-described configuration will be described. 
     As shown in  FIG. 1 , vessel  6  containing fluid A is placed on the upper surface of main body  41  of magnetic stirrer  4 , stirring unit  1  is placed on the bottom surface of vessel  6 , and the magnetic force generated from magnets  46   a and  46   b  attracts magnets  5   a  and  5   b  of base  3  of stirring unit  1 . Then, by driving and rotating motor  45  of magnetic stirrer  4 , stirring unit  1  is rotated in vessel  6 . In this case, although stirring unit  1  rotates at a predetermined position, stirring unit  1  may be made to revolve while rotating the stirring unit  1  by revolving the rotating magnetic field generating section  42  (the same applies to other embodiments.). 
     By rotation of stirring unit  1 , fluid A retained or stagnated in mixing body  2  flows toward an outer periphery of mixing body  2  by receiving centrifugal force, and flows out of mixing body  2  from first through hole  22  of mixing element  21   a  which opens to an outer peripheral surface of mixing body  2  (see  FIGS. 2A and 2B ). On the other hand, fluid A in vessel  6  rotates and flows in a spiral manner toward the central lower portion where mixing body  2  is disposed, and flows into within hollow portion  24  through suction port  20 α, which is the upper opening of hollow portion  24 , from the upper portion of mixing body  2 . Though not shown by any arrow mark in  FIG. 1 , fluid A positioned around lower end of mixing body  2  also flows into within hollow portion  24  through its lower opening, viz., suction port  20 α as shown in  FIG. 2B . Fluid A flowing into hollow portion  24  further receives a centrifugal force acting on stirring unit  1  (in this case, including a force by rotation of stirring unit  1 , the same applies hereinafter), and flows into within mixing body  2  through first through holes  22  of mixing element  21   b  which open to an inner peripheral surface of hollow portion  24 . Then, fluid A flowing from one first through hole  22  at the inflow position passes through other first through hole  22  communicating with the one first through hole  22 , further passes through still other first through hole  22  communicating with the other first through hole  22 , and the like. Thus, fluid A flows within mixing body  2 . 
     In this case, as shown in  FIG. 5A , fluid A flowing within the mixing body  2  passes through the plurality of first through holes  22  of mixing elements  21   a  and  21   b,  and flows in a substantially radial manner from the inner peripheral portion to the outer peripheral portion. At the time, fluid A is divided in an extending direction of the mixing elements  21   a  and  21   b,  and the divided fluids merge or combine. 
     In addition, mixing body  2  has a plurality of mixing elements  21   a  and  21   b  in a stacking direction, and is provided with a plurality of flow paths allowing fluid A to flow in the stacking direction of mixing elements  21   a  and  21   b  by the respective first through holes  22  communicating in the stacking direction. Therefore, when fluid A within mixing body  2  passes through first through holes  22 , fluid A also flows in the stacking direction of mixing elements  21   a  and  21   b  as shown in  FIG. 5  B, and fluid A is also divided in the stacking direction of mixing elements  21   a  and  21   b  to merge. Mixing elements  21   a  and  21   b  shown in  FIG. 2  have different numbers of partition walls in the circumferential direction and in the radial direction from those shown in  FIG. 5 , but are not different in the function. 
     In this way, flow of the fluid A within mixing body  2  spreads not only in planar or two-dimensional division and merging in the extending direction of mixing elements  21   a  and  21   b,  but also in three-dimensional division and merging extending in the stacking direction of mixing elements  21   a  and  21   b . The division and merging are carried out three dimensionally, whereby fluid A is highly mixed by repeating division, merging and the like. When mixing elements  21   a  and  21   b  are stacked one by one, planar and two-dimensional division and merging are performed, but even in this case, fluid A is repeatedly divided, merged, and mixed. 
     As shown in  FIGS. 1, 2A and 2B , stirring unit  1  of this embodiment is provided with hollow portion  24  penetrating in the direction of rotation axis S at the central portion of mixing body  2 . Therefore, fluid A in the upper central portion in vessel  6  is sucked into hollow portion  24  from the upper and lower portions of mixing body  2 , and mixed rapidly within mixing body  2 . 
     As shown in  FIG. 4 , hollow portion  24  of mixing body  2  is formed by stacking second through holes  23  each having an opening area larger than that of each first through hole  22 , and has a sufficiently large opening with respect to first through hole  22 . Accordingly, as shown in  FIG. 5B , the flow resistance when the fluid A flows into hollow portion  24  is smaller than that of first through hole  22  opening on the upper and lower surfaces of mixing body  2 . In addition, hollow portion  24  of mixing body  2  is located in the center of vessel  6  as shown in  FIG. 1 . Therefore, by rotation of stirring unit  1 , fluid A in the upper central portion in vessel  6  opposed to hollow portion  24  can be easily introduced into hollow portion  24  via suction port  20 α as shown in  FIG. 5B  without retention. Then, fluid A sucked into hollow portion  24  receives a centrifugal force by rotation of mixing body  2 , flows into mixing body  2  and passes through each of first through holes  22 , whereby as described above, fluid A is repeatedly divided and merged in the stacking direction and the extending direction of mixing elements  21   a  and  21   b,  respectively, to be highly mixed. 
     Hollow portion  24  of mixing body  2  is not always necessarily located at the center portion in vessel  6 . If desired, by shifting the position of the center portion of stirring unit  1  from the center portion of vessel  6 , hollow portion  24  may deviate from the center portion in vessel  6 . 
     As described above, according to the stirring unit having such a mixing body, the fluid in the center portion of the vessel at the center of rotation is also quickly stirred and the entire fluid can be stirred efficiently. As a result, it is possible to very shorten the time until the entire fluid in the vessel is uniformly stirred. 
     It should be noted that the present invention is not limited to this first embodiment, and various modifications may be made within the scope of the gist of the present invention, and for example, the following modifications are available. 
     Modification  1  of Mixing Body  2   
     First through hole  22  of mixing element  21  may be arranged nonlinearly in the extending direction of mixing element  21 . 
     For example, as shown in  FIG. 6  illustrating a configuration of mixing elements according to a modification  1  of mixing body  2  in this embodiment, mixing elements  21   c  and  21   d  are formed to have partition walls  25 R and  25 C between first through holes  22 , in which partition walls  25 R curving in one direction from the center portion toward the outer side are formed to be in a substantially involute curve toward one direction side, and partitioned and connected by partition walls  25 C extending continuously in the circumferential direction between these partition walls  25 R. Partition walls  25 C extending in the circumferential direction are formed concentrically around the center points of mixing elements  21   c  and  21   d.    
     Thus, by disposing first through holes  22  in an involute shape (nonlinear shape), the flow resistance when the fluid flows through mixing body  2  can be made smaller than in the case where first through holes  22  are arranged in a linear line. 
     Modification  2  of Mixing Body  2   
     The above-described partition walls between first through holes  22  in mixing element  21  may be formed in a curved shape having no edge as seen in a cross sectional direction. For example, as shown in  FIG. 7A  showing a perspective view of the mixing elements according to a modification  2  of mixing body  2  in this embodiment and  FIG. 7B  showing a partial side sectional view of the mixing elements of  FIG. 7A , elliptical or circular, or substantially vertically long elliptical or circular, shapes are formed in the cross-sectional shapes of partition walls  25 R extending in the radial direction and partition walls  25 C extending in the circumferential direction in mixing elements  21   e  and  21   f.    
     The impact at the time of collision by the flow of fluid A in mixing elements  21   e  and  21   f  having partition walls  25 R and  25 C with such a cross-sectional elliptical shape can be reduced on outer surfaces of the partition walls as compared with mixing elements having partition walls with such a rectangular shape as seen in the cross-sectional direction. For example, in the field of cell cultivation such as production of fermented foods by yeast or the like, or cell cultivation such as liquid high density cultivation, even if a fluid A containing substances such as yeast and cells collides with the partition walls when the fluid A is uniformly stirred, the impact is suppressed, and good stirring may be performed without damaging the substance. 
     Modification  3  of mixing body  2   
     The above-described partition wall  25  between first through holes  22  in mixing element  21  may be inclined, if desired. 
     For example, as shown in  FIG. 8A  showing a perspective view of mixing elements according to a modification  3  of mixing body  2  in this embodiment and  FIG. 8B  showing a partial cross-sectional view showing a sectional shape of the mixing elements, partition walls  25 C extending in a circumferential direction in mixing elements  21   g  and  21   h  are inclined so as to spread toward the outer periphery as it goes upwardly, and partition walls  25 R are inclined to one side in the right and left direction. The sectional shapes of partition walls  25 R and  25 C of mixing elements  21   g  and  21   h  are elliptical or substantially elliptical, but may be polygonal such as quadrangular. 
     Mixing elements  21   g  and  21   h  having such inclined partition walls  25 R and  25 C allow the flow of the fluid A within stirring unit  1  to be given directionality by the rotation of stirring unit  1 . In the mixing elements of  FIG. 8A , it is possible to cause the fluid A to spirally flow downward or upward according to the direction of rotation of the stirring unit  1 . 
     Modification  4  of Mixing Body  2   
     The above-described first through holes  22  and second through holes  23  in the plurality of mixing elements  21  stacked in mixing body  2  may be configured to have different sizes for each mixing element  21  as a modification  4  of mixing body  2  in this embodiment. 
     For example, as shown in  FIG. 9A  showing a side sectional view of mixing body  2 , first through holes  22  in a plurality of stacked mixing elements  21   i  and  21   j  may be arranged such that first through holes  22  are larger toward the lower layer side. 
     With such a configuration, since the passage resistance when fluid A passes between first through holes  22  adjacent in the stacking direction within mixing body  2  decreases toward the lower layer side, it is possible within mixing body  2  to reduce the flow rate of fluid A flowing through the upper layer side and increase the flow rate of the fluid A flowing through the lower layer side. 
     Further, as shown in  FIG. 9B  showing a side sectional view of mixing body  2 , second through holes  23  in a plurality of stacked mixing elements  21   m  and  21   n  are formed such that mixing elements  21   m  and  21   n  include second through holes  23  having a larger diameter toward the lower layer side and the inner diameter of a hollow portion  24  is configured to increase toward the lower layer side. 
     With such a configuration, the flow resistance of fluid A flowing in hollow portion  24  decreases toward the lower layer, so that the flow rate of fluid A flowing on the lower layer side can be increased. 
     Modification  5  of Mixing Body  2   
     As a modification  5  of mixing body  2  in this embodiment, mixing body  2  may be configured to be a single member provided with the above-described first through holes  22  and hollow portion  24  without using the structure stacked by the plurality of mixing elements  21 . Mixing body  2  of such a single member may be easily produced by, for example, a 3D printer device. Further, as other mixing body  2 , the above-described hollow portion  24  may be employed in a porous material member having continuous pores serving as first through holes  22 . 
     Modification of Base  3   
     Although the above-described base  3  of  FIGS. 3A to 3C  includes bar body  31  and annular portion  32 , the form of its shape and the like is not particularly limited as far as it does not fall over in this embodiment. 
     As a modification of such base  3 , it may employ bases in various forms, for example, a base  3   a  composed of a bar body having an elliptical columnar form internally with a bar shaped magnet  5  as shown in  FIG. 10A , a base  3   b  composed of a bar body having a flat rectangular columnar form internally with a pair of magnets  5   a  and Sb as shown in  FIG. 10B , a base  3   c  composed of a wheel body having an annular portion internally with a pair of magnets  5   a  and  5   b  as shown in  10 C, and a base  3   d  composed of a cylindrical body having a cylindrical form internally with a pair of magnets  5   a  and  5   b  as shown in  FIG. 11 . Raised portions (screw cylinder portion)  33  having screw holes “h” for mounting mixing body  2  are respectively disposed at both upper end portions of the bar bodies of bases  3   a  and  3   b  as shown in  FIGS. 10A and 10B , and at two locations in a diameter direction of the upper surface of the wheel body of base  3   c  as shown in  FIG. 10C , whereby a gap is formed between mixing body  2  and bases  3   a,    3   b  and  3   c  respectively so that the flow of fluid A under the mixing body  2  is not stagnated. 
     In base  3   d  shown in  FIGS. 11A and 11B  showing a perspective view and a side view of the base, screw holes “h” for mounting mixing body  2  are provided at two positions of 180 degrees apart in an outer peripheral portion of an upper surface of the cylindrical body, and a vertical hole  35  penetrating the upper and lower surfaces is provided in the central portion. Even if mixing body  2  and base  3   d  are in contact with each other, a fluid A flowing in from the lower side of base  3   d  flows through first through holes  22  communicating with vertical hole  35  via hollow portion  24  of mixing body  2 , and is delivered to an outer peripheral portion of mixing body  2  so that fluid A can be satisfactorily stirred without retention the flow of fluid A. 
     It is should be noted that, bases  3   a  and  3   b  shown in  FIGS. 10A and 10B  may have a structure capable of accommodating a bar magnet  5  or magnets  5   a  and  5   b  in a bar body extending in the longitudinal direction. Base  3   c  internally having magnets  5   a  and  5   b  shown in  10 C may have a structure such that other magnets or magnetic substances are disposed at other preferred positions in the annular portion. In a base having such a cylindrical-shaped structure as base  3   d  (see  FIG. 11 ) in which vertical hole  35  does not penetrate the lower surface thereof, a bar magnet may be horizontally accommodated in the lower part of the base. 
     Such a support protrusion  34  as shown in  FIGS. 3B and 3C  are disposed on the bottom surfaces of bar shaped bases  3   a  and  3   b,  and two or more support projections  36  (see  FIG. 11B ) are provided at equal intervals, on bottom faces of wheel-shaped and cylindrical-shaped bases  3   c  and  3   d.    
     As to directions described in this first embodiment, “stacking direction” is synonymous with the direction of the rotation axis of stirring unit  1  (including mixing body  2  and base  3 ), the vertical direction and the like, and “extending direction” is synonymous with the direction orthogonal to the stacking direction, the radial direction and the circumferential direction of mixing elements  21 . 
     Second Embodiment 
       FIG. 12  shows a stirring unit  1 A according to a second embodiment of the present invention. In stirring unit  1 A, a mixing body  2   a  is constituted by a tube body  7  forming open ends upward and sideways, and a base  3   e  is constituted by a disk body  30  holding tube body  7 . 
     Tube body  7  (mixing body  2   a ) and disk body  30  (base  3   e ) may be connected by various members such as a mating structure of unevenness or bonding with an adhesive. Tube body  7  includes a vertical tube  71  extending in the vertical direction and four lateral tubes  72  which are connected to a lower end of vertical tube  71  and extending sideways. Vertical tube  71  is disposed on a rotation axis S of stirring unit  1 A, and the upper end opening thereof serves as a suction port  20 α of fluid A. Lateral tubes  72  are arranged in a cross shape, and the respective side end openings serve as discharge ports  20 β of fluid A. Accordingly, suction port  20 α is located at a position on rotation axis S of stirring unit  1 A, and discharge port  20 β is located at a position outside rotation axis S than suction port  20 α, that is, at a side outer side orthogonal to rotation axis S. Further, vertical tube  71  and lateral tube  72  communicate with each other, and its inside constitutes a flow path of fluid A. If desired, lateral tube  72  may be attached obliquely downward or obliquely upward with respect to longitudinal tube  71 . 
     Though not shown in  FIG. 12 , magnets ( 5   a  and  5   b  of  FIG. 3A ) constituted similarly to the first embodiment are respectively accommodated in two places of base  3   e  at a 180 degree position on the outer peripheral portion of disc body  30 . Further, an arcuate support protrusion ( 34  of  FIG. 3B ) in contact with a bottom surface of a vessel ( 6  of  FIG. 1 ) protrudes from the center of a lower surface of disk body  30  in the same manner as in the first embodiment. In addition, a bar magnet may be housed as a magnet so that both end portions are positioned at the 180 degree position of base  3   e.    
     A method of stirring fluid A by stirring unit  1 A of this second embodiment will be described hereinafter. 
     In the same manner as in the above embodiment shown in  FIG. 1 , as stirring unit  1 A disposed at the bottom of vessel  6  is rotated by the rotating magnetic field from magnetic stirrer  4 , the fluid within each lateral tube  72  is caused by the centrifugal force to flow out to the outside from discharge port  20 β at the side end opening of lateral tube  72 . Then, since fluid A within vertical tube  71  flows into each of lateral tubes  72 , fluid A in the vicinity of the central upper portion in vessel  6  is caused to rotate and flow in a spiral toward tube body  7 , and is drawn into vertical tube  71  from suction port  20 α of the upper end opening of vertical tube  71 . As a result, fluid A on the outer periphery of stirring unit  1 A is mixed by being disturbed by fluid A flowing out from the discharge port  20 β. Thus, fluid A in the upper central portion in vessel  6  is sucked from suction port  20 α of the upper end opening of stirring unit  1 A without retention and flows out from the discharge port  20 β in the side end opening, so that it become possible to efficiently stir fluid A and shorten the time until entire fluid A is uniformly mixed. 
     It is to be noted that lateral tube  72  may be formed to have an I-shape having openings (discharge ports  20 β) at two lateral sides like the tube body  7   a  of the stirring unit  1 A- 1  shown in  FIG. 13A , or to employ lateral tubes of various forms opened at a plurality of lateral locations, as examples of this second embodiment. 
     In addition, like stirring units  1 A- 2  and  1 A- 3  shown in  FIGS. 13B and 13C , the tube body constituting the mixing body  2   a  may be modified to an L-shaped tube body  7   b  having an upper end opening (suction port  20 α) and a side end opening (discharge port  20 β) such that a plurality of the L-shaped tube bodies  7   b  constitute a mixing body  2   a  by assembling the respective tube constituent parts in the longitudinal direction back to back. The respective heights of the upper end openings (suction ports  20 α) of the plurality of L-shaped tube bodies  7   b  may be the same, or, as shown in  FIGS. 13B and 13C , may be different. Thus, by arranging the respective heights of the plurality of suction ports  20 α at different heights (see  FIGS. 13B and 13C ), the fluid A at the respective positions of the upper part and the intermediate part of a central portion of vessel  6  may be sucked in at the same time, so that fluid A in the central portion can be more quickly stirred. In the L-shaped tube type mixed body  2   a,  each suction port  20 α is disposed at a position near the rotation axis S of the stirring unit  1 A- 2  and  1 A- 3 , not at the position on the rotation axis S. 
     Third Embodiment 
       FIGS. 14  A to  14 C show stirring units  1 B,  1 B- 1  and  1 B- 2  as a third embodiment of the present invention. A mixing body  2   b  shown in  FIG. 14A  includes a cylindrical body  8  having openings ( 20 α and  20 β) on its upper and side surfaces respectively and communicating with the respective openings ( 20 α and  20 β) through an internal flow passage  81 , and a base  3   e  is constituted by a disc body  30  having the same outer diameter as that of cylindrical body  8 . 
     One opening on the upper surface of cylindrical body  8  is disposed in the center portion, and the opening portion of this upper surface serves as a suction port  20 α of fluid A. Four openings on the side surface of cylindrical body  8  are arranged at equal intervals, and each opening on this side surface becomes a discharge port  20 β of fluid A. Therefore, in cylindrical body  8  (mixing body  2   a ), suction port  20 α is disposed at the position on rotation axis S of stirring unit  1 B and discharge ports  20 β are located at positions outside rotation axis S than suction port  20 α, that is, disposed at a lateral outside position orthogonal to rotation axis S. This cylindrical body  8  (mixing body  2   b ) has four internal flow passages  81  extending in the lateral direction and four discharge openings  20 β, but this embodiment is not limited thereto. There may be provided a plurality of internal flow passages  81  and discharge openings  20 β. Further, laterally extending internal flow passages  81  may be formed obliquely downward or obliquely upward with respect to internal flow passage  81  extending in the longitudinal direction from suction port  20 α. Base  3   e  has a similar structure to that of the above-described second embodiment ( FIG. 12  and  FIG. 13 ). 
     In addition, in the case where base  3  has a similar structure to that in  FIG. 3 ,  FIG. 10  or  FIG. 11 , opening  20 α on the upper surface of cylindrical body  8  may be penetrated to the lower surface serving as another suction port  20 α as shown in  FIGS. 14B and 14C . In this case, fluid A may also be sucked from the lower surface of cylindrical body  8 . In stirring units  1 B- 1  and  1 B- 2  shown in  FIGS. 14B and 14C , a base  3   d  is an example using base  3   d  shown in  FIG. 11 , and a vertical hole  35  of base  3   d  is arranged to communicate with a through hole in cylindrical body  8  (vertical flow path of internal flow path  81 ) serving as a mixing body  2   b.    
     Further, in the case where cylindrical body  8  has an internal flow path  81  (a longitudinal flow path along a rotation axis S direction and a lateral flow path orthogonal to rotation axis S) communicating with side opening sections  20 β, internal flow path  81  may be easily cleaned by dividing cylindrical body  8   b  if it is constituted by an upper cylindrical body  8   b - 1  and a lower cylindrical body  8   b - 2  which are configured to be vertically divided at a position of internal flow path  81  (lateral flow path) as shown in  FIG. 14C . 
     The stirring units  1 B,  1 B- 1  and  1 B- 2  according to this third embodiment can also achieve the same operation and effect as those of the above-described second embodiment. 
     The stirring units  1 B,  1 B- 1  and  1 B- 2  according to this third embodiment have bases  3   d  and  3   e  as separate bodies from mixing body  2   b,  but mixing body  2   b  may have a cylindrical body integrated with bases  3   d  and  3   e.  In other words, mixing body  2   b  also serving as bases  3   d  and  3   e  may be formed by cylindrical body  8 , and the magnets may be accommodated in the cylindrical body  8 . For example, as in the case of a stirring unit  1 B- 3  shown in  FIG. 15A , when an opening on an upper surface of a cylindrical body  8   c  penetrates to a lower surface serving as suction port  20 α, a magnet of a cylindrical shape, a ring shape, a square shape or the like may be accommodated in cylindrical body  8   c  as a magnet  5  (note that  FIG. 15A  is an example of square magnets  5   a  and  5   b ). As shown a stirring unit  1 B- 4  in  FIG. 15B , when an opening on an upper surface of a cylindrical body  8   c  does not penetrate the lower surface, a bar magnet other than the foresail magnet also may be accommodated in cylindrical body  8  as a magnet  5 . 
     Fourth Embodiment 
       FIGS. 16A to 16C  show perspective views of stirring units IC,  1 C- 1  and  1 C- 2  as a fourth embodiment of the present invention. As shown in  FIG. 16A , a mixing body  2   c  is composed of a structure body  9  in which a disk-shaped annular plate  91  having a through hole in the center and other disk  92  are connected by a plurality of connection walls  93 , openings (suction port  20 α and discharge port  20 β) are disposed on an upper surface and a side surface of structure body  9 , and a base  3   e  is constituted by a disk member  30  having the same outer diameter as the outer diameter of structure body  9 . With such a configuration also, since the outer peripheral end of a gap  90  between annular plate  91  and circular plate  92  separated by the plurality of connection walls  93  becomes discharge port  20 β of a fluid (A), by rotation of stirring unit  1 C, the fluid (A) within a vessel ( 6 ) may be sucked from the opening (suction port  20 α) on the upper surface, and discharged from the side opening (discharge port  20 β) so as to be stirred. In structure body  9  as mixing body  2   c,  four connection walls  93  connecting annular plate  91  and circular plate  92  are provided, but the number is not limited to this and may be smaller or larger than four. Further, like a stirring unit  1 C- 1  shown in  FIG. 16B  connection wall  93  may have an involute shape (nonlinear shape) in a plan view. 
     In a stirring unit  1 C- 2  of this other embodiment  3  as shown in  FIG. 16  C, mixing body  2   c  may be a structure body  9   b  in which a pipe shaped suction tube  94  is connected to annular plate  91 . In this case, one end of suction tube  94  connected to annular plate  91  opens to an upper surface and becomes suction port  20 α of the fluid (A). It should be noted that suction tube  94  may be in the form of a trumpet (not shown in drawings). 
     If desired, base  3   e  of this embodiment may utilize base  3   d  having a vertical hole  35  shown in  FIG. 11A . Another suction port  20 α may be provided on the lower surface of base  3   e  opposed to the suction port  20 α of the upper surface so that the fluid can flow into the stirring unit from both upper and lower suction ports  20 α. 
     Fifth Embodiment 
       FIG. 17  shows a side view of a stirrer  1 D according to a fifth embodiment of the present invention, wherein stirring unit  1 D is formed so as to be elongated as a whole so that it can also be used for a vessel  6 A having a narrow inlet  61  such as an Erlenmeyer flask.  FIGS. 18A to 18F  are perspective views and plan views showing various forms of the stirring unit  1 D of  FIG. 17 . 
       FIG. 18A  is a perspective view of a stirring unit  1 D according to one example in this fifth embodiment. Stirring unit ID includes a mixing body  2   d  constituted by a long thin pipe body  200  opened at both ends, and bases  3   f  which are disposed on both end portions of pipe body  200 . 
     Pipe body  200  serving as mixing body  2   d  has a square pipe shape, and an opening serving as a suction port  20 α for a fluid A of  FIG. 17  which is disposed at a center part of an upper surface in a laterally placed state in which the length direction is horizontal. Although not shown in  FIG. 18A , an opening serving as a suction port may be provided also on the lower surface opposite to suction port  20 α. The openings at both ends of pipe body  200  serve as discharge ports  20 β of fluid A. In stirring unit  1 D, a direction orthogonal to the length direction of pipe body  200  in the laterally placed state of pipe body  200  is defined as a rotation axis S, suction port  20 α is disposed at a position on rotation axis S of stirring unit ID, and each discharge port  20 β is disposed at a position outside rotation axis S than suction port  20 α, that is, at a lateral outside position orthogonal to rotation axis S. 
     Bases  3   f  have disk-shaped magnets  5   a  and  5   b  within the bases which are provided on lower surfaces on both end sides in a laterally placed state of pipe body  200 , respectively. Each base  3   f  has a cylindrical shape, but may be a quadrangular prism shape or the like according to the square pipe shape of pipe body  200 . Bases  3   f  may employ other shaped magnets or magnetic substance than the magnets  5   a  and  5   b,  if desired. The positions of respective bases  3   f  may be arranged closer to the center without arranging them at both ends of pipe body  200 . 
     Since stirring unit  1 D is formed to be long and thin as a whole, as shown in  FIG. 17 , it may be inserted inside vessel  6 A by opposing the end portion thereof to the narrow inlet  61  of vessel  6 A such as an Erlenmeyer flask so as to be disposed on the bottom surface of vessel  6 A. Even if base  3   f  of stirring unit  1  does not face the bottom surface side of vessel  6 A on insertion inside vessel  6 A, base  3   f  of stirring unit ID is moved to be placed on the bottom surface of vessel  6 A by the action of the rotating magnetic field from magnetic stirrer  4  as shown in  FIG. 1 . In the same manner as those of the first embodiment as shown in  FIG. 1 , as stirring unit ID disposed at the bottom of vessel  6 A is rotated by the rotating magnetic field from magnetic stirrer  4 , the centrifugal force causes fluid A within pipe body  200  shown in  FIG. 18A  to flow out from discharge ports  20 β at the openings at both ends of pipe body  200  so that fluid A near the center upper portion in vessel  6 A rotates and flows in a spiral shape toward pipe body  200  to be sacked into pipe body  200  from suction port  20 α at the center of the upper surface thereof. As a result, fluid A in the outer peripheral portion of stirring unit  1 D is mixed by being disturbed by fluid A flowing out from discharge port  20 β. As described above, fluid A in the upper central portion in vessel  6 A can be sucked from suction port  20 α of the upper opening of stirring unit  1 D without retention to flow out from discharge ports  20 β at the openings at both ends of pipe body  200 , so that it is possible to shorten the time until entire fluid A is uniformly mixed. 
     As a modified example of mixing body  2   d  of  FIG. 18A , like a stirring unit  1 D- 1  shown in  FIG. 18B , a cylindrical pipe body  200   a  may be employed or other various tubular pipe bodies may be employed. Further, as in the case of a stirring unit  1 D- 2  shown in  FIG. 18C , There may be employed base  3   b  horizontally disposed at each of the end portions of pipe body  200   a  at point symmetrical positions (different side surfaces) on the side surface along the rotational direction of stirring unit  1 D- 2 . In this case, when stirring unit  1 D- 2  is put into vessel  6 A, stirring unit  1 D- 2  is more likely to be arranged on the bottom surface of vessel  6 A in a posture in which bases  3   g  on both sides face the respective sides of pipe body  200   a.  Stirring unit  1 D- 2  disposed on the bottom surface of vessel  6 A needs to be disposed in such a posture that suction port  20 α of pipe body  200   a  faces upward of the vessel  6 A. However, in a case that suction ports  20 α are disposed on both of the upper and lower surfaces of pipe body  200   a,  any one of the upper and lower surfaces of suction port  20 α faces upward of vessel  6 A, so that it is unnecessary to adjust the attitude of stirring unit  1 D- 2 . 
     Further, if desired, as in the case of a stirring unit  1 D- 3  shown in  FIG. 18D  as a modification, bases  3   g  may have an assembling configuration in which insertion tube portions  37  for inserting a pipe body  200   a  are provided at and both end portions of pipe body  200   a  are inserted into insertion tube portions  37 . Base  3   h  may have a configuration in which a threaded portion is formed in an inner side of each insertion tube portion  37  and threaded portions are also provided on both end portions of pipe body  200   a  so as to be assembled in a screwing manner. If desired, without any threaded portion, base  3   h  may have an insertion type assembling configuration where insertion tube portions  37  are merely fitted into both end portions of pipe body  200   a.    
     Further, the mixing body  2   d  may employ an S-shaped pipe body  200   b  of a stirring unit  1 D- 4  shown in  FIG. 18E , or an I-shaped pipe body  200 C of a stirring unit  1 D- 5  shown in  FIG. 18F , wherein two discharge ports  20 β are arranged to face each other at both end portions of each of pipe bodies  200   b  and  200 C. The mixing body  2   d  may employ other various shaped pipe bodies. In the case of  FIGS. 18E and 18F , bases  3   g  are provided at point symmetrical positions (different side faces) on the side faces of pipe bodies  200   b  and  200   c  along the rotational directions of the stirring units  1 D- 4  and  1 D- 5 , respectively. If desired, bases  3   g  may be provided on both end sides of the lower surface of pipe bodies  200   b  and  200   c.  In the case of the S-shaped pipe body  200   b  shown in  FIG. 18E , it is necessary to determine the rotation direction so that the openings at both ends of pipe body  200   b  may serve as discharge ports  20 β from which fluid A in pipe body  200   b  flows out. Further, as a modification of the present embodiment, mixing body  2   d  may be attached to base  3   i  shown in  FIG. 20A  to be described later. 
     In  FIGS. 18A to 18F  of this embodiment, a pair of magnets  5   a  and  5   b  or magnetic substances are disposed at both end portions of pipe bodies  200 ,  200   a ,  200   b  and  200   c,  respectively, so that the positions of the magnetic poles of magnets  5   a  and  5   b  are opposite to each other. 
     Sixth Embodiment 
       FIG. 19A  is a perspective view of a stirring unit  1 D according to a sixth embodiment of the present invention. For example, as shown in  FIG. 19A , a base  3   f  is constituted by fitting a bar-shaped stirrer  302  into a support base (holding body)  301  in a fittable manner. 
     The bar-shaped stirrer  302  may be constituted by, for example, a rotator holding magnets or magnetic substances. Base  3   f  is provided with attachment holes  303  at a pair of positions of 180 degree on an inner surface of support base  301  formed in an annular shape, and is constituted by fitting and fixing both end portions of bar-shaped stirrer  302  to attachment holes  303 . Screw holes “h” are disposed at a pair of places in a diametrical direction on an upper surface of support base  301 , and a mixing body  2  is attached by screwing screws  11  inserted into mixing body  2  into the screw holes “h”. Thereby, for example, it is possible to easily construct a stirring unit having mixing body  2  by using bar-shaped stirrer  30  of the existing product. 
       FIG. 19B  is a perspective view of a base  3   g  modified from base  3   f  of  FIG. 19A , which is configured such that a recessed groove  304  continuous in a circumferential direction is formed on an inner surface of a support base  301  so that bar-shaped stirrer  302  can be easily fitted to support  301 .  FIG. 19C  is a perspective view of a base  3   h  further modified from base  3   f  of  FIG. 19A , which may be configured such that a support base  300  is formed in a disk shape and a bar-shaped stirrer  302  is fitted and fixed in a fitting groove  305  provided in a bottom surface of the disk. Here, screw holes “h” of screws  11  for attaching mixing body  2  are provided on upper surfaces of support bases  301  and  300  shown in  FIGS. 19B and 19C . 
       FIG. 20A  is a perspective view of a base  3   i  further modified from base  3   f  of  FIG. 19A , and  FIG. 20B  is a cross-sectional view of base  3   i.  Base  3   i  includes a supporting base  301  formed into an annular shape and elongated holes  306  extending in its circumferential direction provided at a pair of positions of an inner side at 180 degrees, in which base  3   i  is constituted by fitting and fixing two ends of bar-shaped stirrer  302  into the respective elongated holes  306 . In this case, in elongated holes  306  into which bar-shaped stirrer  302  is fitted, there is formed a gap so as to communicate an inner side and an outer side of support base  301 , so that a centrifugal force acting on stirring unit  1 D passes a fluid A (not shown) on the inner side of support base  301  through the gap toward the outer side of support base  301 , so that fluid A does not retain on the inner side of support base  301 . Further, on the lower surface of the support base  301 , notches  307  are provided in an opposed portion between the pair of opposed long holes  306 . These notches  307  also make it possible to prevent fluid A from retaining on the inner side of support base  301 . Threaded holes “h” of screws  11  for attaching mixing body  2  to two positions in the diameter direction is provided on an upper surface of support base  301 . 
     In addition to support bases ( 300  and  301 ) shown in  FIGS. 19 and 20 , it is also possible to use a configuration that allows attachment of bar-shaped stirrer  302 . 
     Seventh Embodiment 
       FIG. 21  is a perspective view of a stirring unit  1 E according to a seventh embodiment of the present invention, wherein magnets  5   a  and  5   b  are fixed in a manner to be fitted. A pair of fitting grooves  801  for fitting and fixing magnets  5   a  and  5   b  are provided at a pair of positions in a diameter direction of a lower surface of a cylindrical body  8   d  constituting stirring unit  1 E. Thereby, stirring unit  1 E can be easily constructed. Further, for example, it is possible to easily adjust the magnetic force of stirring unit  1 E by selecting and using magnets  5   a  and  5   b  having different magnetic forces, depending on its purpose, use, and the like. 
     In the stirring unit  1 E, it is preferable to use magnets  5   a  and  5   b  coated with a resin. For example, when cylindrical body  8   d  is made of a fluororesin, magnets  5   a  and  5   b  also coated with a fluororesin is used. The shapes of magnets  5   a  and  5   b  are not limited to the square type as shown in  FIG. 21 , and various shapes such as a cylindrical type may be used. Cylindrical body  8   d  has substantially the same structure as that of cylindrical body  8   c  shown in  FIG. 15A  as a structure of a mixing body  2   b,  but it is not limited to this, and it can be formed in various mixed structures. Cylindrical body  8   d  also has the function of a base ( 3 ) provided with magnets  5   a  and  5   b,  and has the functions of mixing body  2   b  and base  3  integrally. If desired, mixing body  2   b  and base  3  may be formed separately so as to be assembled, and have a fitting groove  801  in which magnets  5   a  and  5   b  are fitted and attached. Also, magnets  5   a  and  5   b  are not limited to the two, but may be constituted by one bar magnet, and cylindrical body  8   d  may be provided with a fitting groove which can be fitted and fixed by the bar magnet in a lateral direction. 
     Holding rings such as annular shapes may be provided on magnets  5   a  and  5   b  respectively, and the respective holding rings may be fitted and fixed on the end portions of tube body  7  as shown in  FIG. 12 . In this case, magnets  5   a  and  5   b  provided with the holding wheels may be provided on the four lateral tubes  72  or only on the two opposed lateral tubes  72 . In this case, stirring unit  1 A is constituted with tube body  7  and magnets  5   a  and  5   b  with holding rings, so that the base  3   e  becomes unnecessary. Likewise, for example, magnets  5   a  and  5   b  with holding rings may be fitted and fixed to both end portions of the tube body  7   a  as shown in  FIG. 13A  so that the base  3   e  is not required. 
     Other Embodiments 
     According to another embodiment of the present invention, the mixing body portion in the above embodiments may be modified to be directly connected to a motor to constitute a mixing body for stirring a fluid in a vessel. 
     That is, there is configured a mixing body (see  FIG. 2 ,  FIGS. 6 to 9  and the like) for stirring the fluid contained in the vessel by rotating around the rotation axis, wherein a suction port and a discharge port for the fluid are provided on a surface of the above-described mixing body, one or two or more holes connecting the suction port and the discharge port are provided within the mixing body, the suction port is disposed at a position on the rotation axis or a position closer to the rotation axis than the discharge port, and the discharge port is disposed at a position outside the rotation axis than the suction port (for example, a position outside in a radial direction orthogonal to the rotation axis). 
     Further, there is provided a mixing body for stirring a fluid contained in a vessel by rotating around the rotation axis (see  FIGS. 12 to 16, 18, 21  and the like), wherein the mixing body includes one or two or more flow paths, one end side opening of the flow path constitutes a fluid suction port, other end side opening of the flow path constitutes a fluid discharge port, the suction port is disposed at a position on the rotation axis or at a position close to the rotation axis, and the discharge port is disposed at a position outside the rotation axis than the suction port (for example, a position outside in a radial direction orthogonal to the rotation axis). 
     As other embodiment of the present invention, the stirring apparatus shown in  FIG. 1  may have a modified construction such that stirring unit  1  is disposed upside down so that base  3  for holding magnets  5   a  and  5   b  in vessel  6  is placed on the upper side of mixing body  2 , a lid is put on vessel  6 , and magnetic stirrer  4  is placed on the lid. 
     Even with the mixing body and stirring device of the above-described other embodiments, like each of the above-described embodiments, the fluid in the central portion of the vessel at the center of rotation is also rapidly stirred to efficiently stir the entire fluid. As a result, it is possible to very shorten the time until the entire fluid in the vessel is uniformly stirred. 
     EXAMPLE 
     Next, in order to ascertain the effect of stirring by the stirring unit of the present invention, the following decolorizing experiment was carried out.  FIGS. 22A to 22D  are photographs to show actual samples for the decolorizing experiment without reference marks, but reference marks corresponding to those in the above described embodiments are added in the following parentheses to help understanding the examples, hereinafter. 
     For the decolorization experiment, an iodine decolorization reaction was used. Specifically, (referring to  FIG. 1 ), a beaker (vessel  6 ) containing an iodine solution (fluid A) was placed on a magnetic stirrer ( 4 ), the stirring unit ( 1 ) of the example was placed in the bottom of the beaker to stir the iodine solution, and the time for decolorization until the iodine solution became transparent was measured after adding an aqueous sodium thiosulfate solution to the stirring iodine solution. The time until the decolorization may be regarded as the time during which the sodium thiosulfate aqueous solution is uniformly mixed with the iodine solution as a whole, that is, the time when the entire fluid (A) is uniformly mixed, and the stirring effect of the stirring unit was verified from the length of the time until the decolorization. 
     The specifications of each solution used in the decolorization experiment are as follows;
         Iodine solution: 20 cc of 0.05 mol/Liodine solution (0.1 N)   Sodium thiosulfate aqueous solution: 4 cc of aqueous solution prepared by dissolving 37.5 g, of sodium thiosulfate in 200 cc of water   Beaker: 3 liters       

     As to stirring units ( 1 ) of Examples 1 and 2, there were used those shown in the photographs of  FIG. 22A  “Example 1” and  FIG. 22B  “Example 2”. 
     A stirring unit ( 1 ) of Example 1 is shown in  FIG. 22  A, and its mixing body ( 2 ) has a structure as shown in  FIG. 2A  (a pair of first through holes  22  in each of mixing elements  21   a  and  21   b  are arranged in a radial direction.), and its base ( 3 ) has a disk structure in which screw cylinder portions ( 33 ) are provided at a pair of positions on an upper surface of disk body  30  of  FIG. 12 . The specification size of the stirring unit ( 1 ) of Example 1 is as follows. 
     The base ( 3 ) has a disk portion with a diameter (outer diameter) of 40 mm and a height of 14 mm, and there is a gap of 5 mm between the base ( 3 ) and the mixing body ( 2 ). The mixing body ( 2 ) is formed by alternately stacking three sets (using a total of twelve mixing elements) each of which is consisting of a pair of mixing elements ( 21   a ) each having a height of 1 mm overlapped with each other and a pair of mixing elements ( 21   b ) each having a height of 1 mm overlapped with each other, and has a diameter (outer diameter) of 37.5 mm, an inner diameter of the hollow portion of 19 mm and a height of 12 mm. 
     A stirring unit ( 1 ) of Example 2 is shown in  FIG. 22B , and its mixing body ( 2 ) has a structure as shown in  FIG. 2  (three first through holes  22  in each of the mixing elements  21   a  and  21   b  are arranged in a radial direction.), and its base ( 3 ) has a disk structure in which screw holes (h) are provided at three positions on an upper surface of disk body  30  of  FIG. 12  and a plurality of through holes vertically penetrating through the base are disposed to reduce its weight. The specification size of the stirring unit ( 1 ) of Example 2 is as follows. 
     The base ( 3 ) has a disk portion with a diameter (outer diameter) of 60 mm and a height of 15 mm, and a gap of 20 mm is provided between disk ( 3 ) and the mixing body ( 2 ). The mixing body ( 2 ) has a three-layered structure formed by alternately stacking three sets (using a total of eighteen mixing elements) each of which is consisting of three mixing elements ( 21   a ) each having a height of 1 mm overlapped with each other and three mixing elements ( 21   b ) each having a height of 1 mm overlapped with each other, and has a diameter (outer diameter) of 54 mm, an inner diameter of the hollow portion of 27 mm and a height of 18 mm. The space between the mixing body ( 2 ) and the base ( 3 ) has a height of 20 mm. 
     As Comparative Example 1, a stirring bar (trade name “Rotor” manufactured by As One Corporation) made of a bar body shown in the photograph of  FIG. 22C  was used. The stirring bar of Comparative Example 1 is a substantially cylindrical shape having a length of 60 mm and a width (diameter) of 8 mm. 
     Further, as Comparative Example 2, there was used a stirring disk (trade name “Crosshead rotator double” manufactured by As One Corporation) having protrusions arranged in a cross shape on upper and lower surfaces of the disk shown in the photograph of  FIG. 22  D. The stirring disk of Comparative Example 2 is a substantially disk-shaped one having a diameter of 40 mm and a height of 14 mm (the thickness of the disk is 5.6 mm, and the height of each of the upper and lower projections is 4.2 mm). 
     As a result of the above decolorization experiments, the time until decolorization was 20 seconds in the stirring unit ( 1 ) of Example 1 and 5 seconds in the case of the stirring unit ( 1 ) in Example 2, whereas in the case of the stirring bar of Comparative Example 1 took 100 seconds, and the stirring disk of Comparative Example 2 took 70 seconds. That is, according to the stirring unit ( 1 ) of the present embodiment, it is possible to complete the mixing of the entire fluid A uniformly in a short time of 1/3.5 or less compared with the stirring unit of the comparative example, so that high stirring performance and high mixing performance could be confirmed. 
     Further, the state of stirrings was observed as shown in the photographs of  FIGS. 23A and 23B  (Example 1 and Example 2). That is, in the stirring units ( 1 ) of Example 1 and Example 2, the solution in the beaker changed to be transparent from the bottom to the top of the beaker as a whole. Accordingly, it can be found that the stirring of a fluid (A) is being performed by the stirring unit ( 1 ) which sucks the solution at the center upper part in the beaker from the upper part of mixing body ( 2 ) into the hollow part and mixes the same within the mixing body ( 2 ) to flow so as to discharge to the outer periphery side of the mixing body ( 2 ). 
     On the other hand, in the stirring units of Comparative Example 1 and Comparative Example 2, as shown in the photographs of  FIGS. 24A and 24B  (Comparative Example 1 and Comparative Example 2), the solution on the outer peripheral side in the beaker changed transparently from the bottom portion of the beaker to the upper portion, and then the solution in the central part with each stirring unit changed to transparent from bottom to top of the beaker. Accordingly, it can be found that the energy of rotation is small at the center part of the stirring unit which is the center of rotation and particularly the movement of the solution is dull at the central upper part most distant from the stirring unit whereby a long time is required for the fluid A in the central portion and the central upper portion to be mixed with the fluid A in the other portion and to be uniformly mixed as a whole. 
     While the invention has been shown and described with reference to one or more particular embodiments thereof, it will be understood by those of skill in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.